Initial serum HCG levels are higher in pregnant women with a male fetus after fresh or frozen single blastocyst transfer: A retrospective cohort study

Abstract

Objective: Substantial previous studies have almost reached an agreement on the gender effect on maternal serum human chorionic gonadotropin (MsHCG) in and after the late first trimester of pregnancy. However, there is little knowledge of the sex-related difference in MsHCG level at the preliminary stage of pregnancy. The purpose of this study is to reveal this difference in women after fresh or frozen single blastocyst transfer (SBT). Materials and methods: A total of 252 fresh SBT cycles and 1486 frozen-thawed SBT cycles collected between June 1, 2014 and May 30, 2017 were retrospectively analyzed in our center. Patients with MsHCG level ≥5 IU/L on day 11 after transfer, achieving a singleton intrauterine pregnancy and subsequent live birth were included. We compared MsHCG levels between women gave birth to a male neonate and those gave birth to a female one in fresh or frozen SBT cycles, respectively. Results: A total of 136 neonates including 57 females and 79 males were born following fresh SBT. The male-female ratio was 1.39:1. The average MsHCG level of male fetuses was higher than that of female fetuses on day 11 after transfer (549.82 ± 253.24 IU/L versus 439.03 ± 198.41 IU/L, P < 0.05). Correspondingly, a total of 431 infants was born after frozen SBT, containing 188 females and 243 males. The male-female ratio was 1.29:1. Initial MsHCG level remained higher in women with a male neonate than the counterparts with a female neonate (894.43 ± 622.17 IU/L versus 758.05 ± 624.33 IU/L, P < 0.05). It was also found the pregnant women following frozen-thawed SBT exhibited higher initial MsHCG level than those following fresh SBT in whether male-bearing or female-bearing gestations. Conclusions: MsHCG levels are higher in pregnant women with a male fetus than those with a female one on day 11 after fresh or frozen SBT. A sex-specific response to the stress in the process of in vitro embryo culture was suggested. Keywords: Gender effect, HCG, Preliminary stage of pregnancy, Sex-specific, Single blastocyst transfer