Association Between Maternal Characteristics and the Risk of Isolated Maternal Hypothyroxinemia

Area of Science:

• Obstetrics and Gynecology
• Endocrinology
• Maternal-Fetal Medicine

Background:

• Isolated maternal hypothyroxinemia (IMH) is a condition affecting pregnant women.
• Understanding risk factors for IMH is crucial for maternal and fetal health.
• Previous studies have explored various maternal characteristics, but comprehensive analysis is needed.

Purpose of the Study:

• To investigate the association between maternal characteristics and isolated maternal hypothyroxinemia (IMH).
• To identify independent risk factors for IMH in a large cohort of pregnant women.
• To inform optimal thyroid function assessment strategies in pregnancy.

Main Methods:

• Cross-sectional study of 54,586 singleton pregnancies at Shanghai First Maternity and Infant Hospital (2014-2020).
• IMH defined as free thyroxine (FT4) <10th percentile with normal TSH.
• Multivariate logistic regression used to identify risk factors including demographics, anthropometrics, and nutritional status.

Main Results:

• Older maternal age (≥35 years), non-local residence, multiparity, pre-pregnancy overweight or obesity, and iron deficiency were significant independent risk factors for IMH.
• These associations were consistent in the overall population and the first-trimester subgroup.
• Adjusted ORs ranged from 1.11 to 1.37 for these identified risk factors.

Conclusions:

• Maternal age, residence, parity, pre-pregnancy BMI, and iron status are significantly associated with IMH.
• These factors are critical for evaluating IMH risk.
• Obstetricians can use these findings to optimize thyroid function screening timing.