Impact of TSH during the first trimester of pregnancy on obstetric and foetal complications: Usefulness of 2.5 mIU/L cut-off value

Objective: An association of pregnancy outcomes with subclinical hypothyroidism has been reported; however, there still exists a strong controversy regarding whether subclinical hypothyroidism ought to be dealt with or not. The objective of the study was to evaluate the association of foetal-maternal complications with first trimester maternal Thyrotropin (TSH) values. Design: A retrospective study in a single tertiary care hospital was performed. Patients: A total of 1981 pregnant women were studied during 2012. Measurements: Thyrotropin (TSH) universal screening was performed between 9 and 12 weeks of gestation. Outcomes included foetal-maternal complications and newborn health parameters. Results: Median TSH was 1.72 (0.99-2.61) mIU/L. The incidence of perinatal loss, miscarriage and stillbirth was 7.2%, 5.9% and 1.1%, respectively. Median TSH of women with and without miscarriage was 1.97 (1.29-3.28) vs 1.71 (0.96-2.58) mIU/L (P=.009). Incidence of pre-eclampsia was 3.2%; TSH in these women was 2.10 (1.40-2.74) vs 1.71 (0.98-2.59) mIU/L in those without (P=.027). TSH in women with dystocia in labour was 1.76 (1.00-2.53) vs 1.68 (0.94-2.59) mIU/L in those who gave birth with normal progression (P=.044). Women with TSH 2.5-5.1mIU/L had a higher risk of perinatal loss [OR 1.589 (1.085-2.329)], miscarriage [OR 1.702 (1.126-2.572)] and premature birth [OR 1.39 (1.013-1.876)], adjusted by mother's age. There was no association with the other outcomes analysed. Conclusions: There is a positive association between maternal TSH in the first trimester of pregnancy and the incidence of perinatal loss and miscarriage. The TSH cut-off value of 2.5mIU/L identified women with higher adverse pregnancy outcomes.