BRIEF REPORT Detection of Thyroid Dysfunction in Early Pregnancy: Universal Screening or Targeted High-Risk Case Finding?

Context: Maternal subclinical hypothyroidism during pregnancy is associated with various adverse outcomes. Recent consensus guidelines do not advocate universal thyroid function screening during pregnancy but recommend testing high-risk pregnant women with a personal history of thyroid or other autoimmune disorders or with a family history of thyroid disorders. Objective: The objective of the study was to assess efficacy of the targeted high-risk case-finding approach in identifying women with thyroid dysfunction during early pregnancy. Design/Setting: This was a single-center cohort study. Patients/OutcomeMeasures:WeprospectivelyanalyzedTSH,free T4 and free T3 in 1560 consecutive pregnant women during their first antenatal visit (median gestation 9 wk). We tested thyroperoxidase antibodies in 1327 (85%). We classified 413 women (26.5%), who had a personal history of thyroid or other autoimmune disorders or a familyhistoryofthyroiddisorders,asahigh-riskgroup.Weexamined whether testing only such a high-risk group would pick up most pregnant women with thyroid dysfunction. Results: Forty women (2.6%) had raised TSH (4.2 mIU/liter). The prevalence of raised TSH was higher in the high-risk group [6.8 vs. 1% in the low-risk group, relative risk (RR) 6.5, 95% confidence interval (CI) 3.3–12.6, P 0.0001]. Presence of personal history of thyroid disease (RR 12.2, 95% CI 6.8–22, P 0.0001) or other autoimmune disorders (RR 4.8, 95% CI 1.3–18.2, P 0.016), thyroperoxidase antibodies (RR 8.4, 95% CI 4.6–15.3, P 0.0001), and family history of thyroid disorders (RR 3.4, 95% CI 1.8–6.2, P 0.0001) increasedtheriskofraisedTSH.However,12of40womenwithraised TSH (30%) were in the low-risk group. Conclusion: Targeted thyroid function testing of only the high-risk group would miss about one third of pregnant women with overt/ subclinicalhypothyroidism.(JClinEndocrinolMetab92:203–207, 2007)