Maternal thyroid deficiency and pregnancy complications: implications for population screening

TLDR

The study aimed to assess how elevated TSH levels relate to pregnancy complications in a cohort of pregnant women. TSH was measured in second‑trimester serum samples, and data on multiple pregnancy outcomes were recorded. Among 9,403 women, 2.2% had TSH ≥ 6 mU/L, and these pregnancies had a 4.4‑fold higher risk of fetal death (3.8% vs 0.9%); other complications were not increased, suggesting that high TSH mainly raises fetal death risk and supports population screening if treatment helps.

Abstract

Objective To examine the relation between certain pregnancy complications and thyroid stimulating hormone (TSH) measurements in a cohort of pregnant women. Methods TSH was measured in sera obtained from women during the second trimester as part of routine prenatal care. Information was then collected about vaginal bleeding, premature delivery, low birthweight, abruptio placentae, pregnancy induced hypertension, need for cesarean section, low Apgar scores, and fetal and neonatal death. Results Among 9403 women with singleton pregnancies, TSH measurements were 6 mU/l or greater in 209 (2.2%). The rate of fetal death was significantly higher in those pregnancies (3.8%) than in the women with TSH less than 6 mU/l (0.9%, odds ratio 4.4, 95% confidence interval 1.9–9.5). Other pregnancy complications did not occur more frequently Conclusion From the second trimester onward, the major adverse obstetrical outcome associated with raised TSH in the general population is an increased rate of fetal death. If thyroid replacement treatment avoided this problem this would be another reason to consider population screening.