Live birth sex ratios are not influenced by blastocyst-stage embryo transfer

Objective: To analyze the sex ratio of infants born after blastocyst-stage transfer of embryos with normal preimplantation FISH genetic screening. Design: Retrospective cohort analysis. Setting: Large academic assisted reproductive technology center. Patient(s): Two hundred twenty-eight patients undergoing fresh IVF cycle with blastocyst transfer. Intervention(s): Preimplantation genetic screening for sex complement. Main Outcome Measure(s): Sex ratio in liveborn infants following blastocyst transfer. Result(s): One thousand thirteen embryos were normal by preimplantation genetic screening of chromosomes 13, 15, 16, 17, 18,21, 22, X, and Y. Four hundred ninety-eight normal embryos were transferred to 228 patients with an overall live birth rate of 41.7%. Transferred blastocysts were selected based upon morphologic assessment. When controlling for the sex of the blastocyst embryo, there was no difference in the male-to-female delivery rate per embryo transferred (27.3% vs. 21.4%) (relative risk=1.28, confidence interval 0.93-1.74). Of the live births 51.7% were male and 48.3% were female (P=.61). Subanalysis revealed no difference in male-to-female delivery rates in groups with a 1:1 ratio of male:female embryos transferred, a non 1:1 ratio transferred, or single-sex transfers. Conclusion(s): Blastocyst-stage embryo transfer does not influence the live birth sex ratio of embryos with normal preimplantation FISH genetic screening. (Fertil Steril (R) 2009;92:913-7. (C)2009 by American Society for Reproductive Medicine.)