The association of maternal thyroid function with placental hemodynamics

Area of Science:

• Obstetrics and Gynecology
• Endocrinology
• Perinatology

Background:

• Thyroid hormone (TH) plays a role in placental development, influencing trophoblast proliferation and invasion.
• Suboptimal placental function is linked to adverse pregnancy outcomes like preeclampsia, fetal growth restriction, and preterm delivery.

Purpose of the Study:

• To investigate the clinical association between maternal thyroid function and placental hemodynamic function during pregnancy.

Main Methods:

• Prospective cohort study of 7069 pregnant women (The Generation R cohort).
• Maternal thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels measured in early pregnancy.
• Placental function assessed via Doppler ultrasound, measuring umbilical and uterine artery resistance indices (PI and RI) and uterine artery notching.

Main Results:

• Higher FT4 concentrations were positively associated with increased umbilical artery PI (second and third trimesters) and uterine artery RI (second trimester).
• Elevated FT4 also correlated with an increased risk of uterine artery notching (third trimester).
• Associations between thyroid function and preeclampsia/birth weight were partially mediated by placental function changes (10.4% and 12.5% respectively).

Conclusions:

• Elevated maternal FT4 in early pregnancy is associated with increased placental vascular resistance in both maternal and fetal compartments.
• These placental changes may contribute to the link between higher FT4 and adverse pregnancy outcomes such as preeclampsia and fetal growth restriction.