Deficit della funzione tiroidea in gravidanza: studio su prevalenza, benessere materno-fetale e valutazione dell'opportunità di uno screening

Abstract

Maternal thyroid diseases during pregnancy has been associated with adverse obstetric and neonatal outcomes. This prospective study evaluates the prevalence of thyroid dysfunction in pregnant women. Serum levels of thyroid-stimulating hormone (TSH), free thyroxine (fT4), and thyroperoxidase antibodies (TPO-Ab) were measured in 951 women at different gestational age of pregnancy. Trimester-specific reference ranges for TSH were used to classify pregnant women into five groups: 1) Overt hypothyroidism (OH); 2) Subclinical hypothyroidism (SCH); 3) Isolated hypothyroxinemia (IH); 4) Low TSH (isolated or associated with high fT4); and 5) Normal. A classification was made also according to the lower and upper ranges provided by the manufacturer for thyroid hormones. Pregnant women who were at a high risk of developing thyroid dysfunction were identified. Altogether, 12.3% of women had hypothyroidism and 2.6% had low TSH. A negative correlation between BMI and fT4, and a positive correlation between BMI and TSH, were observed. The prevalence of both OH and SCH was higher in the high-risk group than in the low-risk group, but 17.9% of women with hypothyroidism were classified at low-risk. Using non-pregnant reference range for TSH, 10.6% of women were misclassificated. The high prevalence of hypothyroidism observed in this study suggests that accurate thyroid screening with trimester specific reference ranges should be warranted, particularly in areas with mild to moderate iodine deficiencies.