BackgroundIn sub-Saharan Africa, one-quarter of all pregnancies occur in adolescents. Children born to adolescent mothers have poorer physical and socio-cognitive development. One reason may be inadequate knowledge on childcare and psychosocial support during pregnancy and post partum, since adolescent mothers have less antenatal care attendance and overall interaction with the health care system. Mobile health technology has been used to relay health information to special groups; however, psychosocial support commonly requires physical interaction.ObjectiveWe aimed to assess the efficacy of an interactive mobile text messaging platform and support groups in improving adolescent mothers’ knowledge and practices as well as infant growth and development.MethodsThis was a quasi-experimental study, conducted among adolescent mothers with infants younger than 3 months, in Homa Bay County, Kenya. Five of the 8 subcounties in Homa Bay County were purposively selected as study clusters. Four subcounties were assigned as intervention clusters and 1 as a control cluster. Adolescent mothers from 2 intervention subcounties received interactive text messaging only (limited package), whereas those from the other 2 subcounties received text messaging and weekly support groups, moderated by a community health extension worker and a counselor (full package); the control cluster only received the end-line evaluation (posttest-only control). The follow-up period was 9 months. Key outcomes were maternal knowledge on childcare and infant development milestones assessed using the Developmental Milestones Checklist (DMC III). Knowledge and DMC III scores were compared between the intervention and control groups, as well as between the 2 intervention groups.ResultsWe recruited 791 mother-infant pairs into the intervention groups (full package: n=375; limited package: n=416) at baseline and 220 controls at end line. Attrition from the intervention groups was 15.8% (125/791). Compared with the control group, adolescent mothers receiving the full package had a higher knowledge score on infant care and development (9.02 vs 8.01;P<.001) and higher exclusive breastfeeding rates (238/375, 63.5% vs 112/220, 50.9%;P=.004), and their infants had higher average DMC III scores (53.09 vs 48.59;P=.01). The limited package group also had higher knowledge score than the control group (8.73 vs 8.01;P<.001); this group performed better than the full package group on exclusive breastfeeding (297/416, 71.4% vs 112/220, 50.9%;P<.001) and DMC III scores (58.29 vs 48.59;P<.001) when compared with the control group. We found a marginal difference in knowledge scores between full and limited package groups (9.02 vs 8.73;P=.048) but no difference in DMC III scores between the 2 groups (53.09 vs 58.29;P>.99).ConclusionsAn interactive text messaging platform improved adolescent mothers’ knowledge on nurturing infant care and the development of their children, even without physical support groups. Such platforms offer a convenient avenue for providing reproductive health information to adolescents.Trial RegistrationPan African Clinical Trials Registry PACTR201806003369302; https://tinyurl.com/kkxvzjse