Uteroplacental Hemodynamics and Perinatal Outcomes in Maternal Hypothyroidism and Thyroid Autoimmunity: A Prospective...

Maternal hypothyroidism and thyroid autoimmunity are frequently implicated in compromised uteroplacental perfusion and subsequent adverse perinatal outcomes. However, the incremental risk conferred by thyroid antibody positivity beyond that of hypothyroidism alone remains a subject of clinical debate.

To examine uteroplacental hemodynamics, via uterine artery (UtA) and umbilical artery (UA) Doppler, and their relation to perinatal outcomes in pregnancies complicated by hypothyroidism with or without thyroid antibodies.

This prospective cohort study, conducted at a tertiary perinatology center between August 2024 and April 2025, enrolled 212 pregnant women (18-24 weeks' gestation) into three groups: (1) hypothyroidism with thyroid antibodies [TPOAb/TGAb] on levothyroxine (n=72); (2) hypothyroidism without antibodies [first-trimester TSH>2.5 mIU/L] on levothyroxine (n=71); and (3) a control group (n=69). Standardized transabdominal UA and bilateral UtA Doppler assessments (S/D ratio, pulsatility index [PI]) were performed according to ISUOG guidelines. Comprehensive perinatal outcomes, including obstetric complications and neonatal status, were recorded.

While BMI was significantly lower in the control group (p=0.008), fetal biometry and birth outcomes remained comparable across all cohorts. Paradoxically, mean UtA PI was significantly higher in controls than in both hypothyroid groups (p<0.001), whereas other Doppler parameters showed no significant differences. The overall obstetric complication rate was 41%, with no statistical variation between groups (p=0.999). Similarly, NICU admission and congenital hypothyroidism rates did not differ significantly.

In this treated, single-center cohort, well-managed maternal hypothyroidism and thyroid autoimmunity were not associated with increased uteroplacental Doppler abnormalities or worse perinatal outcomes compared to controls. These findings suggest that timely and appropriate levothyroxine therapy may successfully mitigate the potential adverse hemodynamic impacts of thyroid dysfunction, though larger multicenter trials are needed to isolate the specific role of autoimmunity.