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

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.