Objective: Pregnant women are at increased risk for morbidity owing to infection with the COVID-19 virus.¹ Vaccination presents an important strategy to mitigate illness in this population. However, there is a paucity of data on vaccination safety and pregnancy outcomes because pregnant women were excluded from the initial phase III clinical trials. Our objective was to describe the maternal, neonatal, and obstetrical outcomes of women who received a messenger RNA (mRNA) COVID-19 vaccination while pregnant during the first 4 months of vaccine availability.

Study design: This was an institutional review board-approved descriptive study of pregnant women at New York University Langone Health who received at least 1 dose of an mRNA COVID-19 vaccination approved by the US Food and Drug Administration (FDA) (Pfizer-BioNTech or Moderna) from the time of the FDA Emergency Use Authorization to April 22, 2021. Eligible women were identified via search of the electronic medical record (EMR) system. Vaccine administration was ascertained via immunization records from the New York State Department of Health. Women were excluded if they were vaccinated before conception or during the postpartum period. Charts were reviewed for maternal demographics and pregnancy outcomes. Descriptive analyses were performed using the R software version 4.0.2 (The R Foundation, Boston, MA).

Results: We identified 424 pregnant women who received an mRNA vaccination. Of those, 348 (82.1%) received both doses and 76 (17.9%) received only 1 dose. The maternal characteristics and vaccination information are shown in Table 1. Of the included women, 4.9% had a history of a confirmed COVID-19 diagnosis before vaccination. After vaccination, no patient in our cohort was diagnosed with COVID-19. In terms of the pregnancy outcomes, 9 women had spontaneous abortions, 3 terminated their pregnancies, and 327 have ongoing pregnancies. Of the women included, 85 delivered liveborn infants. There were no stillbirths in our population. Of the 9 spontaneous abortions, 8 occurred during the first trimester at a range of 6 to 13 weeks' gestation. There was 1 second trimester loss. The rate of spontaneous abortion among women vaccinated in the first trimester was 6.5%. The 327 women with ongoing pregnancies have been followed for a median of 4.6 weeks (range, 0-17 weeks) following their most recent dose. A total of 113 (34.6%) women, initiated vaccination during the first trimester, 178 (54.4%) initiated vaccination during the second trimester, and 36 (11.0%) during the third trimester. Following the vaccination, 2 fetuses (0.6%) developed intrauterine growth restriction, whereas 5 (1.5%) were diagnosed with anomalies. Outcomes for the 85 women who delivered are shown in Table 2. Of the women who delivered, 18.8% were diagnosed with a hypertensive disorder of pregnancy. The rate of preterm birth was 5.9%. One preterm delivery was medically indicated, whereas the remaining 3 were spontaneous. A total of 15.3% of neonates required admission to the neonatal intensive care unit (NICU). Of the NICU admissions, 61.5% were because of hypoglycemia or an evaluation for sepsis. Other reasons for admission included prematurity, hypothermia, and transient tachypnea of the newborn. Of all the neonates, 12.2% were small for gestational age (SGA) per the World Health Organization standards.

Conclusion: This series describes our experience with women who received an mRNA COVID-19 vaccine during pregnancy. In line with other published findings,² we observed no concerning trends. There were no stillbirths. Our 6.5% rate of spontaneous abortion is within the expected rate of 10%,³ and our preterm birth rate of 5.9% is below the national average of 9.5%.⁴ Our rate of pregnancy-related hypertensive disorders is higher than our baseline institutional rate of 9.5%, however, this may be because of the underlying characteristics of our study population or skewing of our small sample size. Our 12.2% rate of SGA neonates is near the expected value based on the definition that 10% of neonates will be SGA at birth. The NICU admission rate is at par with our institutional rate of 12%. To date, most women in this series have had uncomplicated pregnancies and have delivered at-term. Strengths of this study include using the EMR system to identify subjects and gather data. We did not rely on self-enrollment and self-report, thereby reducing selection and recall bias. By performing manual chart reviews, we obtained detailed and reliable information about individual patients. One limitation of this study is the lack of a matched control group consisting of unvaccinated pregnant women and therefore direct conclusions could not be drawn about the relative risks of complications. In addition, our cohort is small and may not be generalizable. Finally, many women included are healthcare workers who had early access to vaccinations. As more pregnant women become eligible for the COVID-19 vaccinations, there is an urgent need to report on the maternal, neonatal, and obstetrical outcomes of COVID-19 vaccinations during pregnancy. The results of this study can be used to counsel and reassure pregnant patients facing this decision.