What is the benefit of screening for thyroid function in pregnant women in the detection of newly diagnosed thyropathies?

Background: Thyroid gland disturbances are the most common endocrine disorders in pregnancy. There are some particular recommendations for the investigation of women in risk groups, but no consensus guidelines for general screening exists at present in the Czech Republic.

Aim: The aim of our study was to determine whether universally conducted screening of pregnant women would reveal a significant number thyropathies.

Material And Methods: We examined 592 pregnant women for thyroid-stimulating hormone (TSH) and free thyroxine (fT4) levels and for autoantibodies against thyroperoxidase (antiTPO) in the 6th - 10th week of their pregnancy.

Results: Levels of TSH, fT4 or antiTPO beyond laboratory reference limits were found by gynaecologists in 214 women (36.1%) and 141 of whom (23.8%) underwent endocrinological examination. In the women without known risk factors (n=91) we found undiagnosed autoimmune thyroiditis in 20 cases (22 %) and in 7 cases (7.7%) some degree of subclinical hypothyroidism was confirmed. Finally, 18 (19.8%) women had hypothyroxinemia in the 1st trimester (fT4 average 8.76 pmol/L) with normal TSH levels. Altogether, a total of 45 women were succesfully identified (49.5% of the endocrinologically examined group without risk factors, i.e. 7.6% of the whole screened group) who warranted monitoring. Of 73 women (12.3%) who underwent screening and, despite recommendation, did not undergo endocrinological examination, there were 55 cases (9.3% of the screened group) with positive levels of antiTPO and with elevation of TSH above the upper normal limit.

Conclusions: Of 592 women in the 6th - 10th week of pregnancy who underwent thyropathy screening, we newly diagnosed 3.4% of women with autoimmune thyroiditis, 1.2% with subclinical hypothyroidism and 3% with hypotyroxinemia, for whom n o thyropathy risk factor had been evident. Thyropathies were identified in 7.6% of probands. We believe that our results support the importance of universal screening in pregnancy.