Effect of Frozen/Thawed Embryo Transfer on Birthweight, Macrosomia, and Low Birthweight Rates.


eMediNexus    11 January 2018

A new study published in the American Journal of Obstetrics and Gynecology compared the effect of frozen/thawed and fresh embryo transfer on birthweight outcomes for singleton, term infants conceived using in vitro fertilization in the United States, between 2007 and 2014, including average birthweight and the risks of both macrosomia (>4000 grams) and low birthweight (<2500 grams). This study utilized data from the Centers for Disease Control and Preventions National Assisted Reproductive Technology Surveillance System to compare birthweight outcomes of live-born singleton, autologous oocyte, and term (37-43 weeks) infants. The findings revealed that frozen/thawed embryo transfer was associated with a 142.34 gram increase in birthweight on an average, when compared to infants born after fresh embryo transfer. Additionally, an interaction between infant sex and embryo transfer type was significant, with frozen/thawed embryo transfer (FET) having a larger effect on male infants by 16 grams. Moreover, the adjusted risk of a macrosomic infant was 1.70 times higher following frozen/thawed embryo transfer than fresh embryo transfer. On the other hand, the adjusted risk of low birthweight following frozen/thawed embryo transfer was 0.52 times higher than fresh embryo transfer. Hence, it was inferred that frozen/thawed embryo transfer is associated with increased average birthweight in singleton, autologous oocytes, and term infants born in the United States, when compared to fresh embryo transfer with a significant interaction between frozen/thawed embryo transfer and infant sex. However, the risk of macrosomia following frozen/thawed embryo transfer is greater than that following fresh embryo transfer, but the risk of low birthweight among frozen/thawed embryo transfer infants is significantly decreased in comparison with fresh embryo transfer infants.

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