Abstract
Objective: To examine the relationship between maternal TSH and free T4 concentrations measured in early pregnancy and the subsequent risk of miscarriage, fetal death or neonatal death.
Method: Cohort study of 2497 native Dutch pregnant women living in the city of Amsterdam. Blood samples were drawn at first booking in which serum TSH, free T4 and TPO-Ab concentrations were determined. Child loss was operationalised as miscarriage, fetal or neonatal death. Women with overt thyroid dysfunction were excluded from analysis.
Results: A total of 32 cases of child loss were observed. The mean TSH and free T4 level in the women who lost their child was 1.45 mlU/L and 9.70 pmol/L compared to 1.1 mlU/L and 9.58 pmol/L in women without child loss. The incidence of child loss increased by 54% (OR=1.54; 95%CI: 1.03 to 2.28; p= 0.034) for every doubling in TSH concentration. The strength of this association did not change after adjustment for smoking, age, parity and the presence of TPO-Ab concentration (adjusted OR for TSH = 1.60; 95%CI: 1.03 to 2.50; p=0.037). The absolute increase in mortality is relatively small; the estimated risk for a woman with a TSH level of 0.49 mlU/l (P10 of total population) is 0.7 percent, increasing to 1.9 % in women with a TSH level of 2.36 mlU/l (P90). We found no association between free T4 concentrations and child loss (OR= 1.57; 95%CI; 0.28 to 8.70; P= 0.606).
Conclusion: In a cohort of native Dutch pregnant women without overt thyroid dysfunction, the risk of having a miscarriage, fetal death or neonatal death increased with higher levels of maternal TSH. Maternal free T4 concentations and child loss were not associated.