Maternal preconception thyroid autoimmunity is associated with neonatal birth weight conceived by PCOS women undergoing their first in vitro fertilization/intracytoplasmic sperm injection

Background Thyroid autoimmunity and polycystic ovary syndrome (PCOS) are the most common endocrinopathies and have close relationships based on common etiology and pathogenesis, including genetic susceptibility, metabolic disorders, hormonal dysregulation, immune response, and inflammatory activation. The co-occurrence of both diseases is associated with adverse reproductive outcomes, but its effect on neonatal outcomes remains largely unknown. We aim to explore the effect of thyroid autoimmunity on neonatal birth weight in PCOS women undergoing IVF/ICSI. Methods This is a retrospective analysis of 486 PCOS women who underwent the first IVF/ICSI cycles and gave birth to 361 singletons and 125 twins during 2018 – 2020 at a reproductive center. The associations between maternal preconception serum thyroid function and autoimmunity indicators and birth weights of the singleton and twin groups were evaluated using generalized linear models (GLMs) and generalized estimate equations (GEEs), respectively. Analyses were further stratified by neonatal sex, maternal age, and maternal preconception BMI to assess the possible interaction effects. Results Maternal preconception serum TPOAb had a significant negative association with singleton birth weight ( P for trends = 0.03). Compared with women in the first tertile of TPOAb, women in the third tertile had a change in singleton birth weight of − 119.72 g (95% CI: − 222.68 g, − 16.70 g). Maternal preconception serum TPOAb had a significant positive association with twin birth weight ( P for trends = 0.01). Compared with women in the first tertile of TPOAb, women in the third tertile had a change in twin birth weight of 138.62 g (95% CI: 33.96 g, 243.30 g). Besides, maternal preconception serum TPOAb had a specific association with increased twin birth weight for female neonates, a specific association with decreased singleton birth weight for PCOS women under 35 years, and a specific association with decreased twin birth weight for overweight PCOS women (all P for interactions < 0.05). Conclusions Maternal preconception thyroid autoimmunity may affect the birth weights of both singleton and twin neonates. Further large cohorts and experimental studies are required to confirm these findings and explore the underlying mechanisms.