Thyroid Function Testing During Pregnancy After Partial Thyroidectomy Versus the General Population: A Nationwide...

Thyroid function screening during pregnancy remains controversial, particularly regarding whether it should be universal or limited to high-risk groups. In addition, there is variability in the degree of surveillance, and recent American Thyroid Association guidelines suggest that risk groups should be followed throughout pregnancy. This study compares thyroid function surveillance between pregnant women following partial thyroidectomy and the general pregnant population.

In this national retrospective matched cohort study, data from the Maccabi Healthcare Services database were analyzed for pregnancies from 2002 to 2023 in women aged ≥18 years. The exposure group included pregnancies in women with a history of partial thyroidectomy, and the nonexposure group had no thyroidectomy. The primary outcome was the frequency of serum thyroid-stimulating hormone (TSH) measurements during pregnancy. The secondary outcome was the incidence of gestational hypothyroidism, defined as elevated TSH or initiation of levothyroxine during pregnancy.

A total of 718 pregnancies in 465 partial thyroidectomy women and 929 022 pregnancies in 398 472 women in the general population were included. TSH was measured in 81% of pregnancies in the partial thyroidectomy group versus 62% in the general population (P < .01). Testing across all 3 trimesters was 18% compared to 3% (P < .01). The prevalence of elevated TSH was significantly higher in the partial thyroidectomy group (9% vs 4%, P < .01).

Thyroid screening during pregnancy remains suboptimal. Pregnancies following partial thyroidectomy receive more frequent monitoring, suggesting recognition of their high-risk status. Findings highlight the need for better implementation of risk-based surveillance.