Higher maternal TSH levels in pregnancy are associated with increased risk for miscarriage, fetal or neonatal death

Background To examine the relationship between maternal TSH and free thyroxine (FT 4 ) concentrations in early pregnancy and the risk of miscarriage, fetal or neonatal death. Method Cohort study of 2497 Dutch women. TSH, FT 4 , and thyroid peroxidase antibodies concentrations were determined at first booking. Child loss was operationalized as miscarriage, fetal or neonatal death. Women with overt thyroid dysfunction were excluded. Results Twenty-seven cases of child loss were observed. The mean TSH and FT 4 level in the women with child loss was 1.48 mU/l and 9.82 pmol/l compared with 1.11 mU/l and 9.58 pmol/l in women without child loss. The incidence of child loss increased by 60% (OR=1.60 (95% confidence interval (CI): 1.04–2.47)) for every doubling in TSH concentration. This association remained after adjustment for smoking, age, parity, diabetes mellitus, hypertension, previous preterm deliveries, and previous preterm stillbirth/miscarriage (adjusted odds ratio=1.80 (95% CI: 1.07–3.03)). This was not true for FT 4 concentrations (OR=1.41 (95% CI: 0.21–9.40); P =0.724). Conclusion In a cohort of pregnant women without overt thyroid dysfunction, the risk of child loss increased with higher levels of maternal TSH. Maternal FT 4 concentrations and child loss were not associated.