The Interactive Effect of Prepregnancy Overweight/Obesity and Isolated Maternal Hypothyroxinemia on Macrosomia

Abstract

Context: Prepregnancy overweight/obesity (OWO) and isolated maternal hypothyroxinemia (IMH) may increase the risk of macrosomia, but little is known about their potential combined effect on macrosomia. Objective: The aim of this study was to assess whether prepregnancy OWO and first-trimester IMH have a synergistic effect on the risk of macrosomia. Methods: A large prospective cohort study in a Chinese population from January 2016 to December 2018 in a tertiary care center. In total, 34 930 pregnant women were included. The main outcome measure was macrosomia. Results: A total of 34 930 participants comprising IMH and euthyroid cases was included in this study. Prepregnancy OWO and first-trimester IMH were independently associated with an increased risk of macrosomia (adjusted odds ratio [OR] 2.48, 95% CI 2.22, 2.78, and adjusted OR 1.65, 95% CI 1.34, 2.01, respectively). The coexistence of prepregnancy OWO and IMH was associated with macrosomia, with an adjusted OR of 5.26 (95% CI 3.9, 7.0) compared with pregnant women without either condition. The additive interaction between prepregnancy OWO and IMH was found to be significant with regard to macrosomia. Conclusion: Prepregnancy OWO and IMH in the first trimester may synergistically increase the risk of macrosomia.