Placental pathologic features in thyroid autoimmunity.

Introduction: Data on placental pathologic features associated with thyreoperoxidase antibodies (TPO Ab) and/or hypothyroidism are limited. The objective of the study was to analyze placental pathologic features of women with TPO Ab positivity.

Methods: Prospective case-control observational study of pregnancy outcome among women screened for TPO Ab positivity and/or isolated hypothyroidism (TSH>4mU/L) during the first trimester of pregnancy. Placenta pathologic findings were recorded according to standard classification.

Results: The overall rates of TPO Ab positivity and isolated hypothyroidism with negative TPO Ab were 9.6% (86/899) and 2.7% (24/899), respectively. Among TPO Ab positive cases, 77.9% (67/86) and 22.1% (19/86) had TSH ≥2.5mU/L or <2.5mU/L, respectively. Compared to controls, mean first and second trimester uterine artery Doppler pulsatility indices (PI) were higher, placental volume and area were lower among cases with TSH≥2.5mU/L. The rates of fetal growth restriction (FGR)/small for gestational age (SGA) (20/67 versus 8/110, Adjusted Odds Ratio (AdjOR) = 10.8,95%CI = 2.7-44), placental pathological features suggesting decidual vasculopathy (37/67 versus 27/110, AdjOR = 2.7,95%CI = 1.1-6.8) or severe maternal vascular malperfusion (MVM) (22/67 versus 9/110, AdjOR = 5.8,95%CI = 1.6-20.1) were higher among cases with TSH ≥2.5mU/L than in controls. Similar results were obtained comparing overall TPO Ab positive subjects to controls. The increased risk of defective placentation and FGR associated with TPO Ab was independent of simultaneous presence of antinuclear antibodies (ANA) and TSH concentration.

Discussion: First trimester TPO Ab positivity was associated with increased rates of abnormal uterine artery Doppler PI and placental features of MVM. This association was independent of TSH concentration and presence of ANA.