Conclusion
Women with a history of RPL demonstrate attenuated levels of serum RLX across all pregnancy trimesters. How dysregulated RLX metabolism may contribute to adverse pregnancy outcome in RPL requires further investigation.
Results
Relaxin rose to a peak at 12 weeks, and gradually declined towards term. At all gestations, women with a history of RPL had lower RLX levels than women without. At 10-12 weeks gestation, uterine artery RI correlated with serum RLX for both RPL and NRPL. In the NRPL group at 10-12 weeks the presence of a notched waveform was associated with higher RLX levels than the absence of a notch (mean 2.1 ng/ml vs. 1.3 ng/ml, P<0.05) and also at 20 weeks (2.1 ng/ml vs. 0.95 ng/ml, P<0.05) but no such difference was seen in the RPL group. Umbilical venous RLX was 4-fold higher in the RPL group than the NRPL group.