Association of Isolated Maternal Hypothyroxinemia with Gestational Diabetes Mellitus and Perinatal Outcomes.

OBJECTIVE

This study aimed to examine the association between isolated maternal hypothyroxinemia (IMH) during the first and second trimesters and the risk of gestational diabetes mellitus (GDM), as well as its association with adverse perinatal outcomes.

METHODS

The study included 2,741 pregnant women who visited the obstetric outpatient clinic at Shanghai General Hospital and underwent routine obstetric examinations between January 2020 and June 2021. Participants diagnosed with IMH in the first trimester were categorized as H1(+), while those without as H1(-). Similarly, those diagnosed with IMH in the second trimester were categorized as H2(+), and those without as H2(-). Based on these classification, four groups were formed: group A H1(-) H2(-), (n = 1,886); group B H1(+) H2(-), (n = 99); group C H1(-) H2(+), (n = 613); and group D H1(+) H2(+), (n = 143). Retrospective analysis was performed to examine clinical data, including pregnancy complications, across all four groups.

RESULTS

The incidence of GDM was significantly higher in groups B, C, and D compared to group A (all p < 0.001), with the following trend: group D > group C > group B > group A. Specifically, group D exhibited the highest incidence of GDM [n% = 93.01 %, p3 < 0.001]). Logistic regression analysis, adjusted for confounding factors identified IMH during the first trimester, IMH during the second trimester, and persistent IMH across both trimesters as significant risk factors for GDM. Notably, the risk of GDM in cases of persistent IMH was 73.97 times higher than the normal risk (aOR = 73.97, p < 0.001). The study also found that isolated maternal hypothyroxinemia (IMH) was significantly associated with adverse perinatal outcomes.

CONCLUSION

IMH during either the first or second trimester, and particularly persistent IMH across both trimesters, is strongly associated with a higher risk of GDM and insulin resistance. Our findings highlight the importance of monitoring and managing IMH during pregnancy to mitigate the risk of adverse perinatal outcomes. Early intervention may improve both maternal and neonatal health.