RESUMO
PURPOSE: The impact of mild subclinical hypothyroidism on pregnancy outcomes in TPOAb-negative women is poorly explored. The aim of the present study was the evaluation in a wide cohort of TPOAb-negative pregnant women the role of subclinical hypothyroidism (SCH) on several pregnancy outcomes. METHODS: The study included women aged ≥ 18 years with a singleton pregnancy without known thyroid disease with serum TSH concentration between 0.4 and 10 mIU/L and TPOAb negative. Data about clinical and demographic features were collected. A blood sample was drown to test TSH, TPOAb, ANA and ENA concentration. The mean uterine artery pulsatility index was measured. Risk of adverse obstetric and fetal outcomes was collected. RESULTS: The cohort included 2135 pregnant women. Pregnant women with TSH 4-10 mUI/L had a significantly higher frequency of family history of thyroid diseases, and personal history of celiac disease diseases, type 1 diabetes mellitus, rheumatic disease, antinuclear antibody (ANA) and anti-extractable nuclear antigen (ENA) positive tests. The risk for pre-eclampsia and small for gestational age (SGA) was significantly higher in pregnant women with first-trimester TSH 4-10 mIU/L. A first-trimester TSH serum level greater than 4 mIU/L was associated with a significant increase in the occurrence of abnormal uterine artery pulsatility index, with a more than threefold increase in the risk of developing pre-eclampsia and with the risk of SGA. CONCLUSIONS: In TPOAb-negative pregnant women, a first-trimester serum TSH level ranging from 4 to 10 mIU/L is significantly and independently linked to an increased uterine artery pulsatility index as well as to negative pregnancy outcomes such as pre-eclampsia, SGA and gestational diabetes.