Lucas A et al. (2005) Postpartum thyroiditis: long-term follow-up. Thyroid 15: 1177–1181

There is a lack of consensus over if, and when, pregnant women should be routinely screened for subclinical thyroid disease. Postpartum thyroiditis is a common condition that occurs during the first year after delivery and is characterized by transient thyrotoxicosis, with or without hypothyroidism. A high proportion of affected women develop persistent hypothyroidism (PH), which negatively influences the outcome of future pregnancies.

Lucas et al. collected long-term follow up data for 42 women (aged 19–40 years) with postpartum thyroiditis, who were followed up every 3 months during the first postpartum year, then once or twice annually thereafter (mean 8.2 ± 2.2 years). During follow-up, 10 women had a subsequent pregnancy, and in 5 of these women postpartum thyroiditis recurred. Over the study period, 14 women developed PH; 4 cases were in women who had a subsequent pregnancy. PH occurred only in women whose postpartum thyroiditis episode included hypothyroidism. The risk of developing PH was higher if the baby was a girl (P <0.05), and increased with increasing TSH concentration during the episode of postpartum thyroiditis (P = 0.004).

The sixth month postpartum is the ideal time to diagnose postpartum thyroiditis and to identify women at risk of developing PH, say the authors. In their study, 37 women had hormone abnormalities at the sixth-month postpartum check, including all those who later developed PH (all 14 of these had TSH levels >6 mIU). Screening would enable levothyroxine treatment to be initiated in those at risk, so that levels of TSH could be normalized before any subsequent pregnancies.