Association of Etonogestrel-Releasing Contraceptive Implant with Reduced Weight Gain in an Exclusively Breastfed Infant: Report and Literature Review.

BACKGROUND: Studies have not found that hormonal contraceptive implants adversely affect breastfeeding, but theoretical concerns exist.

METHODS: We reported a case of reduced weight gain in an exclusively breastfed infant in association with placement of (ENG)-releasing contraceptive implant (Nexplanon) to the FDA Adverse Events Reporting System (FAERS). We further queried reports to FAERS and reviewed published studies of the ENG implant during breastfeeding.

RESULTS: A breastfeeding mother received an ENG implant at 4 weeks postpartum. Her infant was exclusively breastfeeding. One month after implant placement, the infant had lost 145 g, dropping from the 44th percentile to the 6th percentile for growth. During this period, the mother had not returned to work or decreased frequency of feeding. During a 2-year period of FAERS reports, we found one other report of reduced milk supply following ENG implant placement. Among 108 breastfeeding women studied while using the ENG implant, there was one case of lactation failure. If this were not due to chance, the estimated risk of lactation failure with the ENG implant would be 0.9% (95% confidence interval 0.2-5.1%).

CONCLUSION: Given uncertainty regarding the true effect of ENG implants on lactation, it seems prudent for providers to counsel each woman about a possible effect on milk supply so that she can monitor her infant for signs of impaired milk transfer. Patient-centered counseling approaches are needed that allow each woman to assess her own individual tolerance of risk of unplanned pregnancy versus possible risk of lactation failure.