Background: This study was designed to assess the value of using a gonadotrophin-releasing hormone (GnRH) agonist prior to exogenous steroid supplementation for endometrial preparation in frozen-thawed embryo replacement (FER) cycles.
Methods: A prospective randomized trial of 234 patients undergoing FER cycles was conducted. The study population was randomly divided into two groups according to a computer-generated list. In group A (n = 117), a daily dose of 6 mg of oral estradiol valerate was initiated on menstrual day 1 following pituitary suppression using 400 mcg buserelin acetate daily. In group B (n = 117), the same dose of estradiol valerate was initiated on day 1 of bleeding without prior GnRH agonist therapy. In both groups, ovulation monitoring was not undertaken and progesterone pessaries (800 mg daily) were administrated when the endometrial thickness had reached 8 mm or more with embryo transfer taking place 2 days later.
Results: The two groups were comparable with respect to cause of infertility, age at stimulation (32.8 +/- 4 vs 33.2 +/- 3.9 years, P = 0.4), basal FSH level (6.3 +/- 1.7 vs 6.4 +/- 2 IU/l, P = 0.5), number of oocytes collected (16.9 +/- 7.3 vs 16.5 +/- 7.4, P = 0.7) and fertilized normally in the retrieval cycle (11.5 +/- 4.9 vs 11 +/- 4.9, P = 0.4) and number of embryos cryopreserved (6.6 +/- 3.6 vs 6.2 +/- 3.6, P = 0.3). There was no significant difference between the two groups in age at frozen replacement (33.6 +/- 4.2 vs 34 +/- 3.9 years, P = 0.4), duration of the proliferative phase (20.7 +/- 8.6 vs 21 +/- 9.2 days, P = 0.7) and number of thawed embryos replaced (2.3 +/- 0.6 vs 2.2 +/- 0.6, P = 0.2). However, compared with group B, group A achieved significantly higher pregnancy (37.6% vs 24%, OR 1.8, 95%CI 1.1-3.4), clinical pregnancy (24% vs 11.3%, OR 2.5, 95%CI 1.2-5.5) and live birth rates (20% vs 8.5%, OR 2.9, 95%CI 1.2-8).
Conclusion: Medicated frozen embryo replacement cycles timed by endometrial thickness measurement alone without monitoring or suppression of ovarian activity are associated with reduced outcome.