Screening for Thyroid Disorders in the First Trimester of Pregnancy

Abstract

Screening for thyroid disorders during pregnancy is an essential method of detection and could prevent maternal and foetal complications to a considerable extent. The aim of this study was to establish the prevalence of hypothyroidism in pregnancy and to compare universal, targeted and no screening. A prospective-retrospective study was conducted at Neoclinic Medical Centre and University Obstetrics and Gynaecology Hospital “Maichin Dom” between 2018 and 2020 in 420 pregnant women. It was conducted in two parts, with the first part (133 subjects) involving universal screening in the first trimester of newly registered pregnant women during their first obstetrician-gynaecologist visit, and the second part (287 subjects) involving patients in the third trimester who had been screened for thyroid-stimulating hormone (TSH) during pregnancy, with the screening reasons being later on analyzed and, respectively, whether the patients were covered by screening and with what type of screening the patients with thyroid disorder would have been diagnosed. TSH was tested in all patients, and a value of 2.5 mIU/L was accepted as the upper limit of normal for the screening in the first trimester. We found hypothyroidism in 28.6% (38/133) of the patients using universal screening. At least one criterion for increased risk of developing thyroid disorder during pregnancy was present in 78.9% (30/38). Thus, a targeted screening would miss 21.1% (8/38) of the patients in risk. In the second part of the study, the disease was detected in 65.51% (188/287) by either prophylactic testing or universal screening during pregnancy; 31.36% (90/287) of the subjects were diagnosed due to clinical suspicion and 3.13% (9/287) due to family history. Eighty per cent (153/190) of the patients with hypothyroidism were high-risk with the most common criteria being: age above 30 – 63.2% (120/190), autoimmune co-morbidity – 35.8% (68/190) and personal history of miscarriage – 31.1% (59/190). Targeted screening would miss 19.5% (37/190) of them. Most of the patients with clinical hypothyroidism (49/64) would have been classified as high-risk had they been screened universally and therefore 23.4% (15/64) would have been missed in a targeted screening. About 21.1% (8/38) of the patients with hypothyroidism would have been missed with targeted screening and between 28.6% (38/133) and 65.51% (188/287) in the absence of any screening suggesting the need of universal screening establishment at the first visit to an obstetrician-gynaecologist.