Background: Adequate antenatal care is important to both the health of a pregnant woman and her unborn baby. Given South Africa's high rate of cellphone penetration, mobile health interventions have been touted as a potentially powerful means to disseminate health information. This study aimed to increase antenatal health knowledge and awareness by disseminating text messages about clinic procedures at antenatal visits, and how to be healthy during pregnancy.

Methods: Participants recruited were pregnant women attending a primary health care facility in Cape Town. A controlled clinical trial was carried out where the intervention group (n = 102) received text messages staggered according to the week of pregnancy at the time of recruitment. The control group (n = 104) received no text messages. These text messages contained antenatal health information, and were delivered in English, Xhosa or Afrikaans, according to the preference of each participant. A baseline knowledge questionnaire with nine questions was administered prior to the intervention. The same questionnaire was used with added health-related behaviour questions for the intervention group at exit. A modified intention-to-treat analysis was done. To compare the control and intervention group's knowledge, Fisher's exact tests and two-sample t-tests tests were carried out for binary and continuous outcomes, respectively. A focus group of seven participants from the intervention group was then conducted to gain more insight into how the text messages were perceived.

Results: There was substantial loss to follow-up during the study with only 57% of the participants retained at exit. No statistically significant difference was detected between the control and intervention group in any of the nine knowledge questions at exit (all p > 0.05). Responses from the focus group indicated that the text messages acted as a welcome reminder and a source of positive motivation, and were perceived as extended care from the health care provider.

Conclusions: While the intervention failed to improve antenatal health knowledge, evidence from self-reported behaviour and the focus group suggests that text messages have the potential to motivate change in health-seeking behaviour. One should be mindful of loss to follow-up when rolling out mobile health interventions in developing country settings.

Trial registration: Pan African Clinical Trials Registry PACTR201406000841188. Registered 3 June 2014.