['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.', '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.', '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).'] Are higher maternal TSH levels in pregnancy associated with increased risk for miscarriage , fetal or neonatal death?