Background: Human chorionic gonadotropin (hCG) is a marker of placental function, which also stimulates the maternal thyroid gland. Maternal thyroid function can be associated with the pathophysiology of gestational diabetes mellitus (GDM). We aimed to study whether there is an association of hCG concentrations in early pregnancy with GDM and whether it is mediated through maternal thyroid hormones. Methods: This study included 18,683 pregnant women presenting at a tertiary hospital in Shanghai, China, between January 2015 and December 2016. GDM was diagnosed using a 2-hour, 75-g, oral glucose tolerance test (OGTT) according to the American Diabetes Association guidelines. Multivariable logistic or linear regression models were used to identify associations, adjusting for maternal age, education level, family history of diabetes, parity, fetal sex, thyroperoxidase antibody (TPOAb) status, and prepregnancy body-mass index. Results: Higher hCG concentrations were associated with a lower plasma glucose level during the OGTT, but not with fasting plasma glucose or hemoglobin A1c concentrations tested during early pregnancy. hCG in early pregnancy was negatively associated with GDM risk ( p = 0.027). Mediation analysis identified that an estimated 21.4% of the association of hCG-associated GDM risk was mediated through changes in free thyroxine (fT4) concentrations ( p < 0.05). In the sensitivity analysis restricted to TPOAb-positive women, hCG was not associated with GDM ( p = 0.452). Conclusions: Higher hCG levels in early pregnancy are associated with a lower risk of GDM. Maternal fT4 may act as an important mediator in this association.
Context
Pre-pregnancy 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 pre-pregnancy OWO and first-trimester IMH have a synergistic effect on the risk of macrosomia.
Design
A large prospective cohort study in a Chinese population from January 2016 to December 2018.
Setting
A tertiary care center.
Participants
In total, 34,930 pregnant women were included.
Main Outcome Measures: Macrosomia.
Results
A total of 34,930 participants comprising IMH and euthyroid cases was included in this study. Pre-pregnancy OWO and first-trimester IMH were independently associated with an increased risk of macrosomia (adjusted OR, 2.48, 95% CI, 2.22, 2.78, and adjusted OR, 1.65, 95% CI, 1.34, 2.01, respectively). The coexistence of pre-pregnancy OWO and IMH was associated with macrosomia, with an adjusted OR of 5.26 (95% CI, 3.9, 7.0) compared to pregnant women without either condition. The additive interaction between pre-pregnancy OWO and IMH was found to be significant with regard to macrosomia.
Conclusions
Pre-pregnancy OWO and IMH in the first trimester may synergistically increase the risk of macrosomia.
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