INTRODUCTION: Lactogenesis is triggered by withdrawal of circulating progesterone after birth, thus leading to theoretical concern that progesterone-containing contraception may decrease breast milk production. While current studies show no adverse effects of implant placement on milk supply, there has not yet been a study to evaluate the effects with immediate postpartum implant use. METHODS: We performed a prospective cohort study from June 2019 through April 2021. Inclusion criteria were breastfeeding females ages 18 years and older. Exclusion criteria were use of other hormonal contraception, contraindications to breastfeeding, or inability to breastfeed due to neonatal circumstances. Participants were enrolled prior to discharge and assigned to an implant (progesterone-containing contraceptive) or control group. Follow-up data were collected at the 6-week visit or via telephone. Statistics included Student’s t-test and chi square, and were performed using an alpha level of 0.05. RESULTS: A total of 151 participants were enrolled. There was no significant difference between breastfeeding rates at 6 weeks postpartum (implant 65.0% vs control 70.5%, P=.537). Cohorts differed in marital status (P<.001) and age (P=.017), with implant users more likely to be younger and single. CONCLUSION: Interim analysis indicates that immediate implant use does not have a significant effect on postpartum breastfeeding rates. Due to interruptions during a global pandemic, the study did not reach goal participation of implant users to adequately power the primary outcome. Despite younger age, potential lack of partner support, and a trend toward first-time mothers, immediate postpartum implant use did not appear to affect breastfeeding rates.
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