Universal screening detects twice more thyroid disorders in early pregnancy than targeted high-risk case finding
Jiri Horacek1, Sylvie Spitalnikova2, Blanka Dlabalova1, Eva Malirova1, Jaroslav Vizda1, Ioannis Svilias1, Catherine McGrath1 & Jaroslav Maly1
Screening of thyroid disorders in pregnancy has been a matter of controversy. Recent recommendations favour targeted high-risk case finding though this approach may miss a significant number of those affected (Vaidya et al. JCEM 2007).
Among 398 non-selected women in the 10th week of pregnancy, thyrotropin (IRMA) >3.5 mIU/l was found in 10.3%, free thyroxine (RIA) <10 pmol/l in 2% and thyroperoxidase antibodies (RIA) >50 IU/ml in 8.3%; a total of 65 (16.3%) had at least one abnormality. After exclusion of those already treated for autoimmune thyroiditis, those identified were offered further endocrine examination.
Of these, 51 were seen in our endocrine clinic (incl. ultrasonography) and followed up; only 2 were left untreated, while levothyroxine was started in 49 (mostly 50 μg/day, range 50100): in 42 for autoimmune thyroiditis and in 34 for hypothyroidism (in 27 for both).
They were also assessed according to 10 accepted high-risk criteria (Abalovich et al. JCEM 2007). Only 23 (45%) of positively screened women fulfilled at least one high-risk criterion: most commonly positive family history (31%), history of miscarriage or preterm delivery (14%), and positive personal history (8%).
In our cohort, therefore, over half (55%) of pregnant women with clear abnormalities suggestive of autoimmune thyroiditis and/or hypothyroidism, and indicated for treatment, would be missed if only those with high-risk criteria were examined.