Timing of etonogestrel-releasing implants and growth of breastfed infants.

OBJECTIVE: To evaluate the growth of breastfed infants whose mothers had inserted an etonogestrel-releasing implant in the immediate postpartum period. METHODS: An open randomized controlled and parallel trial of postpartum women who were block-randomized to early (up to 48 hours postpartum before discharge) or conventional (at 6 weeks postpartum) insertion of an etonogestrel implant. The primary outcome was average infant weight at 12 months (360 days) and a difference of equal to or greater than 10% between groups was considered clinically significant. The secondary outcomes were infants height and head and arm circumferences. These variables were measured at baseline and at 14 40 90 180 270 and 360 days postpartum. The mixed-effects linear regression model was used to evaluate the outcomes with a power of 80% and a significance level of 1% for the primary outcome and 0.3% for secondary outcomes as a result of correction for multiple hypothesis testing. RESULTS: From June to August 2015 a total of 100 women were randomized: 50 to early and 50 to conventional postpartum etonogestrel insertion. Sociodemographic characteristics were similar between the groups except for educational attainment. The conventional insertion group included a higher proportion of women with 8 or more years of formal education than the early insertion group (88% [44/50] compared with 70% [35/50] P=.02). There was no difference in infant weight at 360 days between the groups (early [mean±standard deviation] 10.1±1.2 kg compared with conventional 9.8±1.3 kg mean difference estimate 0.3 kg 95% confidence interval 0-0.7 kg). Growth curves height and head and arm circumferences did not differ between the groups. CONCLUSION: There is no difference in growth at 12 months among breastfed infants whose mothers underwent early compared with conventional postpartum insertion of the etonogestrel implant. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT02469454