Luteal phase support does not improve the clinical pregnancy rate of natural cycle frozen-thawed embryo transfer: a retrospective analysis.

Objective: To evaluate pregnancy outcomes with and without use of luteal phase support (LPS) in frozen-thawed embryo transfer (FET) performed in natural cycles (NC).

Study Design: Retrospective analysis. Before 1st July 2009, two doses of 1500 IU intramuscular human chorionic gonadotrophin were given on the day of FET and 6 days after the transfer. Such practice was stopped after 1st July 2009. The pregnancy outcomes of NC FET with and without LPS were compared.

Results: A total of 408 NC FET cycles were analysed. Demographic data, embryo quality, clinical pregnancy rates and miscarriage rates were comparable with and without LPS. By univariate logistic regression, the only significant factors predicting the clinical pregnancy rate were the women's age, the number of embryos transferred, the number of top quality embryos before and after cryopreservation, and the average number of blastomeres after thawing. Only the women's age (OR 0.944, 95%C.I. 0.893-0.998, p=0.044) remained to be a significant predictor of clinical pregnancy rate by multivariate logistic regression.

Conclusion: The pregnancy outcomes of NC FET were similar with or without LPS. The women's age was the significant factor affecting the clinical pregnancy rate. A randomised trial should be carried out to confirm the results.