Thyroid hormones are essential for the development of the brain in fetal and early postnatal life. Research has shown that in cases with overt hypo- and hyperthyroidism, both low and high TSH and FT4 levels have been associated with child loss.

This study by Benhadi et al. looked at the relationship between TSH and FT4 in early pregnancy and the risk of miscarriage, fetal and neonatal death. The study excluded women with known thyroid disease or overt hypo- or hyperthyroidism and used 2497 Dutch women, who had participated in the Amsterdam Born Children and their Development population-based cohort study. The women received a questionnaire during their pregnancy to assess demographic, health and lifestyle questions, and TSH and FT4 levels were assayed.

In the twenty-seven cases of child loss observed the mean TSH and FT4 level 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 authors conclude that the risk of child loss was increased with higher TSH levels and no association was seen with FT4 levels in this large sample of women. They suggest that pregnancy outcome may be improved by treating women with slightly elevated TSH. Benhadi, N., Wiersinga, W.M., Reitsma, J.B., Vrijkotte, T.G.M., Bonsel, G.J. European Journal of Endocrinology 2009 160: 985-991, DOI: 10.1530/EJE-08-0953