Elevated first-trimester serum relaxin concentrations in pregnant women following ovarian stimulation predict prematurity risk and preterm delivery

Abstract

Objective: To determine whether ovarian stimulation would result in higher circulating relaxin concentrations and whether this hyperrelaxinemia would be associated with prematurity.

Methods: Two groups of women were studied: 1) women achieving pregnancy after ovarian stimulation (n = 114) and 2) women achieving pregnancy without treatment (n = 37). Serum was obtained at 6-12 weeks' gestational age; fetal number was determined by transvaginal ultrasound. Prematurity risk or preterm delivery was determined from the obstetric record. A specific human relaxin enzyme-linked immunosorbent assay was used to measure serum relaxin concentrations. Hyperrelaxinemia was defined as levels greater than 3 standard deviations above the weighted mean of levels in normal unstimulated singleton pregnancies at 6-12 weeks' gestation.

Results: An association was found between prematurity risk or premature delivery and peripheral relaxin concentrations during weeks 6-12 of pregnancy in women having ovarian stimulation and in women having multiple gestations. Circulating relaxin concentrations greater than 16 ng/mL in women having ovarian stimulation and levels greater than 7 ng/mL in women who had multiple gestations predicted prematurity risk or premature delivery in 50% of the women.

Conclusions: These data demonstrate that after ovarian stimulation, some women have highly elevated circulating first-trimester relaxin concentrations. First-trimester hyperrelaxinemia identifies a group of women at risk for prematurity who can be monitored aggressively.