EFFECTS OF IMMEDIATE POSTPARTUM USE OF INJECTABLE CONTRACEPTION ON HUMAN MILK FEEDING

Abstract

Objectives

US guidelines permit depot medroxyprogesterone acetate (DMPA) use among people intending to feed their infant with their milk. However, DMPA use is often restricted in practice due to lack of high-quality evidence. We evaluated the effect of immediate postpartum DMPA use on the timing of lactogenesis stage-II (LS=II).

Methods

The initial design randomly assigned adults who delivered a full-term infant in 2019-2021 to receive within 48 hours of delivery: DMPA, placebo injection, or no injection. Due to low enrollment, we changed in 2021-2023 to a non-randomized design using propensity score weighting for analysis and balancing recruitment for obesity and delivery method. Here, we combined data from both designs to compare immediate postpartum DMPA use (n=55) vs. control arm (n=95). We defined noninferiority a priori as being met if the upper bound of a two-sided 95% confidence interval (CI) for the mean difference in time to LS-II between the immediate DMPA and control groups was <6 hours.

Results

In the unweighted analysis, the mean time to LS-II was 57.8 hours in the DMPA arm (SD=29.4) and 64.1 hours in the control arm (SD=36.1). Using propensity score weighting to make the arms comparable with respect to age, race, and gravidity, we found that the mean time to LS-II was 5.4 hours shorter (95% CI, -16.3, 5.4) for women in the DMPA relative to control arm.

Conclusions

We found no evidence that DMPA use inhibits the initiation of LS-II. Our findings support the immediate postpartum use of DMPA among those intending to engage in human milk feeding.