Effects of Screening for Thyroid Dysfunction in Pregnant Women, Linked to Neonatal Screening for Congenital Hypothyroidism

Abstract

Thyroid dysfunction frequently occurs in women of childbearing age. Thyroid abnormality during pregnancy causes premature birth, miscarriage and toxemia of pregnancy. It also influences the thyroid function of newborn infants. In order to strengthen the neonatal screening program for congenital hypothyroidism, a screening program for thyroid dysfunction in early pregnancy was instituted in Hokkaido prefecture. TSH and free T4 in dried blood specimens from pregnant women were measured with commercial kits. This program contributed to the high frequent detection of thyroid dysfunction in pregnant women. Furthermore, to rapidly detect thyroid abnormality in infants and to investigate the screening effect, we checked the thyroid function of infants born to mothers with thyroid dysfunction at ages 1, 3 and 5 days. If the mother has hyperthyroidism, thyroid function measurements in infants born to mothers in a control group are transiently more abnormal than those in infants of screened mothers. Maternal hyperthyroidism is, therefore, better managed in screened women than in women in a control group. It is very important for the thyroid function of the fetus and newborns to control the maternal hyperthyroidism appropriately. Linkage of the two screening programs brought a synergistic effect to both.