If thyroid function is found to be abnormal in pregnant women, there is generally no significant adverse effect on the fetus if the thyroid function can be well controlled during pregnancy. 1. Fetal malformation: Pregnant women with severe thyroid function abnormalities may suffer from fetal malformation due to the use of therapeutic drugs and abnormal metabolic ability; 2. Fetal growth retardation: Pregnant women with hyperthyroidism have hyper-metabolic ability and their body hormones are out of balance, while the fetus needs to take in maternal nutrients and hormones for growth and development, which may cause fetal In addition, abnormal thyroid function may cause fetal growth retardation. In addition, abnormal thyroid function can cause premature birth or low birth weight babies; 3, fetal intelligence impairment: pregnant women with severe abnormal thyroid function can directly affect fetal neurological development, such as severe untreated hypothyroidism during pregnancy can lead to a reduction in fetal IQ, and in severe cases, the fetus can be born with cretinism; 4, congenital hyperthyroidism and hypothyroidism: because maternal TSH receptor antibodies can pass through the placenta, which in turn stimulates the fetus In addition, if a pregnant woman with hyperthyroidism takes a lot of anti-thyroid drugs during treatment, it can suppress the fetal thyroid function and cause congenital hypothyroidism in the newborn.