RELATIONSHIP BETWEEN THE DAY OF EMBRYO-TRANSFER AND THE OUTCOME IN HUMAN IN-VITRO FERTILIZATION AND EMBRYO-TRANSFER

Purpose: To clarify the optimal dare of embryo transfer (ET), we retro spectively analyzed the relationship between the day of ET and the out come in human in vitro fertilization and embryo transfer (IVF-ET). Met hod: Of a total of 307 human IVF-ET cycles performed at Kyoto Universi ty Hospital between January 1990 and March 1994, we focused on 207 cas es of IVF-ET cycles in which two or three good-quality embryos were tr ansferred. These 207 IVF-ET cycles consisted of 54 Day 2 ET cycles, 79 Day 3 ET cycles, 46 Day 4 ET cycles, and 28 Day 5 ET cycles. We compa red the pregnancy and live-birth (plus ongoing pregnancy) rates among these four ET groups. Results: The pregnancy rates of ET on Days 2 to 4 were not significantly different, whereas Day 5 ET produced a signif icantly lower pregnancy rare (Day 2, 29.6%; Day 3, 32.9%; Day 4, 30.4% ; Day 5, 10.7%). Similar results were obtained for the live-birth (plu s ongoing pregnancy) rates (Day 2, 20.3%; Day 3, 18.9%; Day 4, 17.9%; Day 5, 7.1%). Conclusions: These results suggest that the day of ET do es not fundamentally affect the pregnancy rate in human IVF-ET provide d that transfer is made before Day 5.