Low prevalence of clinically high-risk women and pathological thyroid ultrasound among pregnant women positive in universal screening for thyroid disorders.

BACKGROUND: It is controversial whether screening program for thyroid disorders in pregnancy should be universal or targeted case-finding. To evaluate the relationship between history, laboratory parameters and thyroid ultrasound (TUS) in pregnant women positive in universal screening.

SUBJECTS AND METHODS: The screening included investigation of serum TSH (thyroid stimulating hormone) and TPOAb (antithyroperoxidase antibodies) in 5,520 unselected pregnant women in the 9-11th gestational week. In 822 the screening was positive: abnormal TSH (> 3.67 or < 0.06 mIU/l) and/or positive TPOAb (> 143 kIU/l). 200 consecutive women with positive screening were included it the study.

RESULTS: 41 women (21%) had transient gestational hyperthyroidism (TGH) and 159 (79%) had a thyroid pathology: 10 (5%) overt hypothyroidism; 76 (38%) subclinical hypothyroidism, 7 (3.5%) overt hyperthyroidism and 66 (33%) euthyroid TPOAb positivity. After exclusion of TGH, only 74/159 (47%) women were classified as high-risk for thyroid disease according to their history. There were no significant clinical and laboratory differences between the high- vs. low-risk women, except for higher proportion of FT4<75th percentile (P=0.008) and larger thyroid volume in the high-risk group (P=0.04). Finally, only 66/126 (52%) of TPOAb-positive pregnant women had autoimmune pattern in TUS in comparison with 41/49 (84%) TPOAb-positive non-pregnant control women of comparable age (P<0.001).

CONCLUSIONS: Less than half of the positively screened pregnant women can be classified as high-risk and almost half of them had not autoimmune pattern in TUS. High- and low-risk pregnant women have similar clinical and laboratory characteristics.