Transfer of fresh versus frozen embryos among underweight women: significant difference in the occurrence of small-for-gestational-age infants
摘要
Given that underweight women are at high risk for delivering small-for-gestational-age (SGA) infants, this study aimed to investigate whether frozen-embryo transfer (frozen-ET) reduces the occurrence of SGA compared to fresh-embryo transfer (fresh-ET) in this population undergoing assisted reproductive technology (ART).
MethodsThis retrospective unicentric cohort study included 1140 underweight women (pre-pregnancy body mass index [BMI] < 18.5 kg/m2) who delivered live-born singletons after ART treatment. Women with medical conditions potentially affecting neonatal birthweight were excluded. A total of 340 and 800 subjects were included in the fresh-ET and frozen-ET groups, respectively. Maternal and fetal perinatal outcomes were compared between groups. Continuous variables were compared using independent samples t-test, and categorical variables were analyzed by chi-square test. Binary logistic regression was used to identify risk factors for SGA, adjusting for potential confounders.
ResultsSingleton deliveries following frozen-ET exhibited a significantly lower SGA rate (13.8% [47/340] vs. 7.3% [58/800], p < 0.001) and higher birthweight (3127.8 ± 465.3 g vs. 3260.4 ± 437.9 g, p < 0.001) compared to fresh-ET. No significant differences were observed in rates of preterm birth, congenital anomalies, or maternal pregnancy complications. After adjusting for confounders, frozen-ET was associated with a significantly lower risk of SGA (adjusted OR 0.42, 95% CI 0.22–0.78; p = 0.006).
ConclusionsAmong underweight women undergoing ART, frozen-ET was associated with a lower risk of SGA compared to fresh-ET, without an observed increase in maternal or neonatal complications. These findings suggest that pre-pregnancy BMI may be relevant to the individualization of embryo transfer strategies, although further prospective studies are warranted to confirm this association.