Review
doi: 10.1002/14651858.CD007950.pub3.
Effects and safety of periconceptional oral folate supplementation for preventing birth defects
Affiliations
- PMID: 26662928
- PMCID: PMC8783750
- DOI: 10.1002/14651858.CD007950.pub3
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Review
Effects and safety of periconceptional oral folate supplementation for preventing birth defects
Cochrane Database Syst Rev.
.
Abstract
Background: It has been reported that neural tube defects (NTD) can be prevented with periconceptional folic acid supplementation. The effects of different doses, forms and schemes of folate supplementation for the prevention of other birth defects and maternal and infant outcomes are unclear.
Objectives: This review aims to examine whether periconceptional folate supplementation reduces the risk of neural tube and other congenital anomalies (including cleft palate) without causing adverse outcomes in mothers or babies. This is an update of a previously published Cochrane review on this topic.
Search methods: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 August 2015). Additionally, we searched the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (31 August 2015) and contacted relevant organisations to identify ongoing and unpublished studies.
Selection criteria: We included all randomised or quasi-randomised trials evaluating the effect of periconceptional folate supplementation alone, or in combination with other vitamins and minerals, in women independent of age and parity.
Data collection and analysis: Two review authors independently assessed the eligibility of studies against the inclusion criteria, extracted data from included studies, checked data entry for accuracy and assessed the risk of bias of the included studies. We assessed the quality of the body of evidence using the GRADE approach.
Main results: Five trials involving 7391 women (2033 with a history of a pregnancy affected by a NTD and 5358 with no history of NTDs) were included. Four comparisons were made: 1) supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials); 2) supplementation with folic acid alone versus no treatment or placebo (one trial); 3) supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials); and 4) supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials). The risk of bias of the trials was variable. Only one trial was considered to be at low risk of bias. The remaining studies lacked clarity regarding the randomisation method or whether the allocation to the intervention was concealed. All the participants were blinded to the intervention, though blinding was unclear for outcome assessors in the five trials.The results of the first comparison involving 6708 births with information on NTDs and other infant outcomes, show a protective effect of daily folic acid supplementation (alone or in combination with other vitamins and minerals) in preventing NTDs compared with no interventions/placebo or vitamins and minerals without folic acid (risk ratio (RR) 0.31, 95% confidence interval (CI) 0.17 to 0.58); five studies; 6708 births; high quality evidence). Only one study assessed the incidence of NTDs and showed no evidence of an effect (RR 0.07, 95% CI 0.00 to 1.32; 4862 births) although no events were found in the group that received folic acid. Folic acid had a significant protective effect for reoccurrence (RR 0.34, 95% CI 0.18 to 0.64); four studies; 1846 births). Subgroup analyses suggest that the positive effect of folic acid on NTD incidence and recurrence is not affected by the explored daily folic acid dosage (400 µg (0.4 mg) or higher) or whether folic acid is given alone or with other vitamins and minerals. These results are consistent across all four review comparisons.There is no evidence of any preventive or negative effects on cleft palate (RR 0.73, 95% CI 0.05 to 10.89; three studies; 5612 births; low quality evidence), cleft lip ((RR 0.79, 95% CI 0.14 to 4.36; three studies; 5612 births; low quality evidence), congenital cardiovascular defects (RR 0.57, 95% CI 0.24 to 1.33; three studies; 5612 births; low quality evidence), miscarriages (RR 1.10, 95% CI 0.94 to 1.28; five studies; 7391 pregnancies; moderate quality evidence) or any other birth defects (RR 0.94, 95% CI 0.53 to 1.66; three studies; 5612 births; low quality evidence). There were no included trials assessing the effects of this intervention on neonatal death, maternal blood folate or anaemia at term.
Authors' conclusions: Folic acid, alone or in combination with vitamins and minerals, prevents NTDs, but does not have a clear effect on other birth defects.
Conflict of interest statement
Luz Maria De‐Regil: I am a full time staff of the Micronutrient Initiative, an International NGO that supports research projects and large scale programmes to improve vitamin and mineral consumption among the most vulnerable populations.
Juan Pablo Peña‐Rosas and Pura Rayco‐Solon: The World Health Organization gratefully acknowledges the financial contribution of the Bill & Melinda Gates Foundation, Micronutrient Initiative, the Centers for Disease Control and Prevention (CDC), the US Agency for International development (USAID), the Global Alliance for Improved Nutrition (GAIN) and Harvest Plus towards the work in the area of nutrition. Donors do not fund specific guidelines and do not participate in any decision related to the guideline development process, including the composition of research questions, membership of the guideline groups, conduct and interpretation of systematic reviews, or formulation of recommendations.
Ana C Fernández‐Gaxiola: none known.
Figures
Study flow diagram.
Methodological quality graph: review authors' judgements about each methodological quality item presented as percentages across all included studies.
Methodological quality summary: review authors' judgements about each methodological quality item for each included study.
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 1 Neural tube defects (All).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 2 Neural tube defects (by scheme).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 3 Neural tube defects (by daily dose).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 4 Neural tube defects (by timing of supplementation).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 5 Neural tube defects (by history of an affected pregnancy ‐recurrence).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 6 Neural tube defects (by folate compound).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 7 Neural tube defects (by micronutrient composition).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 8 Neural tube defects (by malaria setting at time of the study).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 9 Cleft lip (All).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 10 Cleft lip (by scheme).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 11 Cleft lip (by daily dose).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 12 Cleft lip (by timing of supplementation).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 13 Cleft lip (by history of an affected pregnancy ‐recurrence).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 14 Cleft lip (by folate compound).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 15 Cleft lip (by micronutrient composition).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 16 Cleft lip (by malaria setting at the time of the study).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 17 Cleft palate (All).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 18 Cleft palate (by scheme).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 19 Cleft palate (by daily dose).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 20 Cleft palate (by timing of supplementation).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 21 Cleft palate (by history of an affected pregnancy ‐recurrence).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 22 Cleft palate (by folate compound).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 23 Cleft palate (by micronutrient composition).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 24 Cleft palate (by malaria setting at the time of the study).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 25 Congenital cardiovascular anomalies (All).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 26 Congenital cardiovascular anomalies (by scheme).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 27 Congenital cardiovascular anomalies (by daily dose).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 28 Congenital cardiovascular anomalies (by timing of supplementation).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 29 Congenital cardiovascular anomalies (by history of an affected pregnancy ‐recurrence)).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 30 Congenital cardiovascular anomalies (by folate compound).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 31 Congenital cardiovascular anomalies (by micronutrient composition).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 32 Congenital cardiovascular anomalies (by malaria setting at the time of the study).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 33 Other congenital anomalies (All).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 34 Other congenital anomalies (by scheme).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 35 Other congenital anomalies (by daily dose).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 36 Other congenital anomalies (by timing of supplementation).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 37 Other congenital anomalies (by history of an affected pregnancy ‐recurrence).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 38 Other congenital anomalies (by folate compound).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 39 Other congenital anomalies (by micronutrient composition).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 40 Other congenital anomalies (by malaria setting at the time of the study).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 41 Miscarriage (All).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 42 Miscarriage (by scheme).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 43 Miscarriage (by daily dose).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 44 Miscarriage (by timing of supplementation).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 45 Miscarriage (by history of an affected pregnancy ‐recurrence).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 46 Miscarriage (by folate compound).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 47 Miscarriage (by micronutrient compound).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 48 Miscarriage (by malaria setting at the time of the study).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 49 Spina bifida.
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 50 Anencephaly.
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 51 Stillbirths.
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 52 Elective termination of pregnancy for fetal anomalies.
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 53 Low birthweight (less than 2500 g).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 54 Macrosomia (birthweight greater than 4000 g).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 55 Preterm birth (less than 37 weeks' gestation).
Comparison 1 Supplementation with any folate versus no intervention, placebo or other micronutrients without folate (five trials), Outcome 56 Multiple pregnancy.
Comparison 2 Supplementation with folic acid alone versus no treatment or placebo (one trial), Outcome 1 Neural tube defects (All).
Comparison 2 Supplementation with folic acid alone versus no treatment or placebo (one trial), Outcome 2 Miscarriage (All).
Comparison 2 Supplementation with folic acid alone versus no treatment or placebo (one trial), Outcome 3 Spina bifida.
Comparison 2 Supplementation with folic acid alone versus no treatment or placebo (one trial), Outcome 4 Anencephaly.
Comparison 2 Supplementation with folic acid alone versus no treatment or placebo (one trial), Outcome 5 Elective termination of pregnancy for fetal anomalies.
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 1 Neural tube defects (All).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 2 Neural tube defects (by scheme).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 3 Neural tube defects (by daily dose).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 4 Neural tube defects (by timing of supplementation).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 5 Neural tube defects (by history of an affected pregnancy ‐recurrence).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 6 Neural tube defects (by folate compound).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 7 Neural tube defects (by micronutrient composition).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 8 Neural tube defects (by malaria setting at time of the study).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 9 Cleft lip (All).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 10 Cleft lip (by scheme).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 11 Cleft lip (by daily dose).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 12 Cleft lip (by timing of supplementation).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 13 Cleft lip (by history of an affected pregnancy ‐recurrence).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 14 Cleft lip (by folate compound).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 15 Cleft lip (by micronutrient composition).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 16 Cleft lip (by malaria setting at the time of the study).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 17 Cleft palate (All).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 18 Cleft palate (by scheme).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 19 Cleft palate (by daily dose).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 20 Cleft palate (by timing of supplementation).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 21 Cleft palate (by history of an affected pregnancy ‐recurrence).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 22 Cleft palate (by folate compound).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 23 Cleft palate (by micronutrient composition).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 24 Cleft palate (by malaria setting at the time of the study).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 25 Congenital cardiovascular anomalies (All).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 26 Congenital cardiovascular anomalies (by scheme).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 27 Congenital cardiovascular anomalies (by daily dose).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 28 Congenital cardiovascular anomalies (by timing of supplementation).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 29 Congenital cardiovascular anomalies (by history of an affected pregnancy ‐recurrence)).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 30 Congenital cardiovascular anomalies (by folate compound).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 31 Congenital cardiovascular anomalies (by micronutrient composition).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 32 Congenital cardiovascular anomalies (by malaria setting at the time of the study).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 33 Other congenital anomalies (All).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 34 Other congenital anomalies (by scheme).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 35 Other congenital anomalies (by daily dose).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 36 Other congenital anomalies (by timing of supplementation).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 37 Other congenital anomalies (by history of an affected pregnancy ‐recurrence).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 38 Other congenital anomalies (by folate compound).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 39 Other congenital anomalies (by micronutrient composition).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 40 Other congenital anomalies (by malaria setting at the time of the study).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 41 Miscarriage (All).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 42 Miscarriage (by scheme).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 43 Miscarriage (by daily dose).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 44 Miscarriage (by timing of supplementation).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 45 Miscarriage (by history of an affected pregnancy ‐recurrence).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 46 Miscarriage (by folate compound).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 47 Miscarriage (by micronutrient compound).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 48 Miscarriage (by malaria setting at the time of the study).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 49 Spina bifida.
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 50 Anencephaly.
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 51 Stillbirths.
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 52 Elective termination of pregnancy for fetal anomalies.
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 53 Low birthweight (less than 2500 g).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 54 Macrosomia (birthweight greater than 4000 g).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 55 Preterm birth (less than 37 weeks' gestation).
Comparison 3 Supplementation with folate plus other micronutrients versus other micronutrients without folate (four trials), Outcome 56 Multiple pregnancy.
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 1 Neural tube defects (All).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 2 Neural tube defects (by scheme).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 3 Neural tube defects (by daily dose).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 4 Neural tube defects (by timing of supplementation).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 5 Neural tube defects (by history of an affected pregnancy ‐recurrence).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 6 Neural tube defects (by folate compound).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 7 Neural tube defects (by micronutrient composition).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 8 Neural tube defects (by malaria setting at time of the study).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 9 Cleft lip (All).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 10 Cleft lip (by scheme).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 11 Cleft lip (by daily dose).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 12 Cleft lip (by timing of supplementation).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 13 Cleft lip (by history of an affected pregnancy ‐recurrence).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 14 Cleft lip (by folate compound).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 15 Cleft lip (by micronutrient composition).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 16 Cleft lip (by malaria setting at the time of the study).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 17 Cleft palate (All).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 18 Cleft palate (by scheme).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 19 Cleft palate (by daily dose).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 20 Cleft palate (by timing of supplementation).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 21 Cleft palate (by history of an affected pregnancy ‐recurrence).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 22 Cleft palate (by folate compound).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 23 Cleft palate (by micronutrient composition).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 24 Cleft palate (by malaria setting at the time of the study).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 25 Congenital cardiovascular anomalies (All).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 26 Congenital cardiovascular anomalies (by scheme).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 27 Congenital cardiovascular anomalies (by daily dose).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 28 Congenital cardiovascular anomalies (by timing of supplementation).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 29 Congenital cardiovascular anomalies (by history of an affected pregnancy ‐recurrence)).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 30 Congenital cardiovascular anomalies (by folate compound).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 31 Congenital cardiovascular anomalies (by micronutrient composition).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 32 Congenital cardiovascular anomalies (by malaria setting at the time of the study).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 33 Other congenital anomalies (All).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 34 Other congenital anomalies (by scheme).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 35 Other congenital anomalies (by daily dose).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 36 Other congenital anomalies (by timing of supplementation).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 37 Other congenital anomalies (by history of an affected pregnancy ‐recurrence).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 38 Other congenital anomalies (by folate compound).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 39 Other congenital anomalies (by micronutrient composition).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 40 Other congenital anomalies (by malaria setting at the time of the study).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 41 Miscarriage (All).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 42 Miscarriage (by scheme).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 43 Miscarriage (by daily dose).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 44 Miscarriage (by timing of supplementation).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 45 Miscarriage (by history of an affected pregnancy ‐recurrence).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 46 Miscarriage (by folate compound).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 47 Miscarriage (by micronutrient compound).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 48 Miscarriage (by malaria setting at the time of the study).
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 49 Anencephaly.
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 50 Stillbirths.
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 51 Elective termination of pregnancy for fetal outcomes.
Comparison 4 Supplementation with folate plus other micronutrients versus the same other micronutrients without folate (two trials), Outcome 52 Multiple pregnancy.
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Botto 2006 {published data only}
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Cavalli‐Sforza 2005 {published data only}
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- Christian P. Personal communication 28 September 2007.
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- Christian P, Darmstadt GL, Wu L, Khatry SK, LeClerq SC, Katz J, et al. The effect of maternal micronutrient supplementation on early neonatal morbidity in rural Nepal: a randomised, controlled, community trial. Archives of Disease in Childhood 2008;93(8):660‐4. - PubMed
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Daly 1995 {published data only}
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Daly 1997 {published data only}
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- Daly S, Mills JL, Molloy AM, Conley M, Lee YJ, Kirke PN, et al. Minimum effective dose of folic acid for food fortification to prevent neural tube defects. Lancet 1997;350:1666‐9. - PubMed
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- Daly S, Mills JL, Molloy AM, Conley M, McPartlin J, Lee YJ, Young PB, Kirke PN, Weir DG, Scott JM. Low‐dose folic acid lowers plasma homocysteine levels in women of child‐bearing age. QJM 2002;95(11):733‐40. - PubMed
Doyle 2001 {published data only}
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Drazkowski 2002 {published data only}
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Ellison 2004 {published data only}
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- Ellison J, Clark P, Walker ID, Greer IA. Effect of supplementation with folic acid throughout pregnancy on plasma homocysteine concentration. Thrombosis Research 2004;114:25‐7. - PubMed
Eskes 2000 {published data only}
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Field 1991 {published data only}
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Geisel 2003 {published data only}
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Gunaratna 2015 {published data only}
Hague 2003 {published data only}
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Hayes 1996 {published data only}
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Itikala 2001 {published data only}
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Khambalia 2009 {published data only}
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- Khambalia A. Periconceptional Iron Supplementation and Iron and Folate Status Among Pregnant and Non‐Pregnant Women in Rural Bangladesh [thesis]. Toronto: University of Toronto, 2009.
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Lee 2005 {published data only}
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Manizheh 2009 {published data only}
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Mathews 1999 {published data only}
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McNulty 2013 {published data only}
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Melli 2008 {published data only}
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Molster 2007 {published data only}
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Nelen 2000 {published data only}
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Pitkin 2007 {published data only}
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Pritchard 1991 {published data only}
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Ramakrishnan 2003 {published data only}
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Ray 2007 {published data only}
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Ray 2008 {published data only}
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Robbins 2005 {published data only}
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- Robbins J M, Tilford JM, Bird TM, Cleves MA, Reading JA, Hobbs CA, et al. Hospitalizations of newborns with folate‐sensitive birth defects before and after fortification of foods with folic acid [erratum appears in Pediatrics. 2006 Dec;118(6):2608]. Pediatrics 2006;118(3):906‐15. - PubMed
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- Robbins JM, Cleves MA, Collins HB, Andrews N, Smith LN, Hobbs CA, et al. Randomized trial of a physician‐based intervention to increase the use of folic acid supplements among women. American Journal of Obstetrics & Gynecology 2005;192(4):1126‐32. - PubMed
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Rolschau 1999 {published data only}
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- Rolschau J, Kristoffersen K, Ulrich M, Grinsted P, Schaumburg E, Foged N. The influence of folic acid supplement on the outcome of pregnancies in the county of Funen in Denmark. Part I. European Journal of Obstetric & Gynecology and Reproductive Biology 1999;87(2):105‐10; discussion 103‐4. - PubMed
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- Ulrich M, Kristoffersen K, Rolschau J, Grinstead P, Schaumburg E, Foged N. The influence of folic acid supplement on the outcome of pregnancies in the county of Funen in Denmark. Part II. Congenital anomalies A randomised study. European Journal of Obstetrics & Gynecology and Reproductive Biology 1999;87:111‐3. - PubMed
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- Ulrich M, Kristoffersen K, Rolschau J, Grinsted P, Schaumburg E, Foged N. The influence of folic acid supplement on the outcome of pregnancies in the county of Funen in Denmark. Part III. Congenital anomalies. An observational study. European Journal of Obstetrics & Gynecology and Reproductive Biology 1999;87(2):115‐8; discussion 103‐4. - PubMed
Rosenthal 2008 {published data only}
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- Rosenthal J, Milla G, Flores A, Yon M, Pfeiffer C, Umaña E, et al. Effect of different dosage and administration schedules of folic acid on blood folate levels in a population of Honduran women of reproductive age. Public Health Nutrition 2008;11(8):822‐30. - PubMed
Sayers 1997 {published data only}
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- Sayers GM, Hughes N, Scallan E, Johnson Z. A survey of knowledge and use of folic acid among women of child‐bearing age in Dublin. Journal of Public Health Medicine 1997;19(3):328‐32. - PubMed
Schorah 1993 {published data only}
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- Schorah CJ, Wild J. Fortified foods and folate intake in women of child‐bearing age. Lancet 1993;341(8857):1417. - PubMed
Schwarz 2008 {published data only}
Shaw 1995 {published data only}
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- Shaw GM, Lammer EJ, Wasserman CR, O'Malley CD, Tolarova MM. Risks of orofacial clefts in children born to women using multivitamins containing folic acid periconceptionally. Lancet 1995;346(8972):393‐6. - PubMed
Shaw 2006 {published data only}
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Shrimpton 2002 {published data only}
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van der Put 1998a {published data only}
van Rooij 2004 {published data only}
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- Rooij IA, Ocke MC, Straatman H, Zielhuis GA, Merkus HM, Steegers‐Theunissen RP, et al. Periconceptional folate intake by supplement and food reduces the risk of nonsyndromic cleft lip with or without cleft palate. Preventive Medicine 2004;39(4):689‐94. - PubMed
Wald 2004 {published data only}
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- Wald NJ. Folic acid and the prevention of neural‐tube defects. New England Journal of Medicine 2004;350(2):101‐3. - PubMed
Walsh 2007 {published data only}
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- Walsh T, O'Broin S, Cooley S, Donnelly J, Collins C, McMillan H, et al. Maternal folate status and neural tube defects in Ireland: the need for a national food fortification program. Irish Medical Journal 2007;100(5):469‐72. - PubMed
Watson 1999 {published data only}
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- Watson LW. The epidemiology of folate and neural tube defects: a community intervention and ongoing issues. Australasian Epidemiologist 2003;10:6‐8.
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- Watson M, Watson L, Bell R, Halliday J. The increasing knowledge of the role of periconceptional folate in Victorian women of child‐bearing age: follow‐up of a randomised community intervention trial. Australian & New Zealand Journal of Public Health 2001;25(5):389‐95. - PubMed
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- Watson M, Watson L, Bell R, Halliday J, Burford N, Brennecke S. Increasing knowledge of the role of folate in women of child‐bearing age in Victoria ‐ a randomised trial. 2nd Annual Congress of the Perinatal Society of Australia & New Zealand; 1998 March 30‐April 4; Alice Springs, Australia. 1998:114.
Wehby 2012 {published data only}
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- Javois L. Birth defects treatment and prevention program: oral cleft prevention program (ongoing trial). ClinicalTrials.gov (http://clinicaltrials.gov/) (accessed 21 March 2006).
Wen 2005 {published data only}
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- Wen SW, Walker M. An exploration of health effects of folic acid in pregnancy beyond reducing neural tube defects. Journal of Obstetrics & Gynaecology Canada: JOGC 2005;27(1):13‐9. - PubMed
Westphal 2004 {published data only}
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- Westphal LM, Polan ML, Trant AS. Double‐blind, placebo‐controlled study of FertilityBlend: a nutritional supplement for improving fertility in women. Clinical and Experimental Obstetrics and Gynecology 2006;33(4):205‐8. - PubMed
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- Westphal LM, Polan ML, Trant AS, Mooney SB. A nutritional supplement for improving fertility in women: a pilot study. Journal of Reproductive Medicine 2004;49(4):289‐93. - PubMed
Wilcox 2007 {published data only}
Zeng 2008 {published data only}
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- Li Q, Yan H, Zeng L, Cheng Y, Liang W, Dang S, et al. Effects of maternal multimicronutrient supplementation on the mental development of infants in rural western China: follow‐up evaluation of a double‐blind, randomized, controlled trial. Pediatrics 2009;123(4):e685‐92. - PubMed
References to ongoing studies
Bailey 2014 {published data only}
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- Bailey LB. Folic acid supplementation in pregnant women: dose response (FAPREG). ClinicalTrials.gov (http://clinicaltrials.gov/) [accessed 27 September 2014] 2014.
Hekmatdoost 2011 {published data only}
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- Hekmatdoost A. Comparison of the effect of folic acid and 5‐methyltetrahydrofolate (5MTHF) on serum folate and homocysteine levels, and abortion rates in women suffering from recurrent abortion. IRCT Iranian Registry of Clinical Trials (www.irct.ir) (accessed 8 July 2011).
Koren 2013 {published data only}
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- Koren G. Optimizing periconceptional and prenatal folic acid supplementation. ISRCTN Registry (http://www.isrctn.com/) (accessed 9 September 2015).
Linet 2011 {unpublished data only}
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- Linet M. Follow‐up study of late effects of periconceptional folic acid in mothers and offspring in the community intervention program population: the Chinese children and families study. http://clinicaltrials.gov/show/NCT01365975 (accessed 5 December 2013).
Additional references
Bailey 2015
Balshem 2010
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