Impact of method of endometrial preparation for frozen blastocyst transfer on pregnancy outcome: a retrospective cohort study.

<bold>Objective: </bold>To determine whether live birth rates differ by type of endometrial preparation in frozen embryo transfer (FET) cycles.<bold>Design: </bold>Retrospective cohort study.<bold>Setting: </bold>Academic fertility center.<bold>Patient(s): </bold>Reproductive-aged women undergoing autologous vitrified-warmed blastocyst FETs.<bold>Intervention(s): </bold>Comparison of two methods of endometrial preparation: programmed FET (known as group A: luteal phase GnRH agonist suppression, oral E2, and IM P starting 5 days before ET) versus unstimulated FET (known as group B: hormone and ultrasound monitoring for follicle collapse to time transfer).<bold>Main Outcome Measure(s): </bold>Live birth rates in group A and group B.<bold>Result(s): </bold>Group A consisted of 923 cycles, and group B consisted of 105. When stratified by age at transfer, there was no difference in any of the measured outcomes, including live birth rates in adjusted models (adjusted odds ratio 1.0, 95% confidence interval 0.6-1.5), except in patients older than 40 years. These patients in group B had a 100% failure rate (n = 6).<bold>Conclusion(s): </bold>In most women, unstimulated endometrial preparation with luteal support before FET has similar success compared with exogenous hormone preparation. Women older than 40 years may benefit from programmed FETs owing to the challenges of increased cycle variability expected in that age group. [ABSTRACT FROM AUTHOR]