Postpartum factors and natural fibroid regression

ObjectiveMany fibroids regress with pregnancy or postpartum involution. We sought to identify factors that might inhibit or enhance this natural regression.Study DesignWe used a prospective cohort of women with fibroids (n = 494) determined by ultrasound screening during the early first trimester identified from the Right from the Start study. Ultrasounds were repeated 3-6 months postpartum (n = 279). Logistic regression analyses were used to identify factors associated with fibroid regression (>50% reduction in volume).ResultsPostpartum progestin users had significantly less fibroid regression (P = .01), whereas there was no association for combined estrogen-progestin use. Cesarean delivery and fever (hypothesized to inhibit regression) and breast feeding (hypothesized to enhance regression) were not associated with fibroid regression.ConclusionProgestin use in the postpartum period may limit regression of fibroids, consistent with prior literature on progesterone's role in fibroid development. Research into progestin-only treatments in critical reproductive periods is needed.