Journal Article

Identifying a possible factor for the increased newborn size in singleton pregnancies after assisted reproductive technology using cryopreserved embryos, in comparison with fresh embryos

Shitanaka, Manami, Shoda, Akiko, Kubo, Michiyo, Shimada, Nobutaka, Okazaki, Satiko, Nakao, Kazuki, Horikawa, Michiharu, Negishi, Hiroaki, Ishii, Rena, Fujita, Yoko, Taketani, Yuji, Enomoto, Megumi, Suzuki, Minori, Okawa, Riho

2018

Overview

Purpose To determine whether the cycle regimens that are used for endometrial preparation are associated with the birthweight (BW) after assisted reproductive technology (ART) using frozen‐thawed embryo transfer (FET). Methods The BW of singletons who were born by ART using FET was compared retrospectively, according to whether a FET was conducted in a hormone replacement therapy cycle (HRT, n = 403) or an ovulatory cycle (OVL, n = 117). The BW after timed intercourse (NAT, n = 162) also was investigated. Results There were no significant differences in the age of the mothers, percentage of primiparas, gestational periods, Body Mass Index, and sex ratio between the HRT and OVL cycles. The average BW from HRT was significantly greater than that of OVL. The BW from HRT was also greater, compared with NAT, while statistical significance was not achieved between OVL and NAT. The putative factors affecting the BW, such as ovarian stimulation protocols, endometrial thickness, and the stage and quality of embryos, could not explain the difference in the BW between the HRT and OVL cycles. Conclusion An increased BW from ART using FET seems to be ascribable to conditions of the endometrium, but not cryopreservation procedures per se, which might provide a mechanistic framework for understanding heavier neonates who are born by FET. We explored the mechanism of how birth weight of babies born from assisted reproductive technology using frozen‐thawed embryos is higher compared with fresh embryos transfer. The data presented here implicate that higher birth weight of babies born using frozen‐thawed embryos is not intrinsic to the technology of cryopreservation itself, but is related to how the endometrium is prepared for embryo transfer.

• Publisher: John Wiley & Sons, Inc,John Wiley and Sons Inc,Wiley
• Subject: assisted reproductive technology / Birth weight / birthweight / Body mass index / Comparative analysis / Cryopreservation / Embryo transfer / Embryonic development / endometrial preparation / Endometrium / frozen embryo / Hormone replacement therapy / Hormone therapy / Infertility / Neonates / Original / Pregnant women / Reproductive technologies / Reproductive technology / Sex ratio / Technology application