Pregnancy and Autoimmune Thyroid Disease

Thyroid hormones impact female reproduction in several ways. Both too much or too little can cause lighter periods or stop menstruation in as many as 20-70% of women with thyroid disease. Studies have shown that women with hyperthyroidism continue to ovulate while those in a severe hypothyroid state may not. In cases of mild or subclinical hypothyroidism, there have been studies that show increased rates of miscarriage, stillbirth or prematurity. Other studies with infertility patients have shown no correlation with random miscarriage.

Iodine deficiency in pregnancy can result in decreased thyroid levels in the baby and in severe cases can result in cretinism, a form of mental retardation that can range from mild to severe. Even mild hypothyroidism is thought to impact fetal brain development.

Autoimmune thyroid disease (Graves' or Hashimoto's) is also linked with an increased risk of gestational diabetes, a form of diabetes that occurs only during pregnancy and usually resolves after pregnancy. This form of diabetes is often treated with diet only, but may require insulin treatment. There is some risk of prematurity and hypoglycemia (low blood sugar) in the baby.

Thyroid levels change somewhat during a normal pregnancy, however there is good evidence to support screening all pregnant women for thyroid disease. The studies reviewed for this article certainly support the importance of normal thyroid levels in achieving a positive outcome of the pregnancy. Women with diagnosed hypothyroidism may need dosages increased slightly during pregnancy.

Women with Graves' disease or hyperthyroidism need to be maintained on anti-thyroid drugs (ATD) with frequent monitoring during pregnancy. There is no identified significant effect of ATD on the fetus. Thyroid ablation with I131 (RAI) is not an option during the pregnancy. However, occasionally one may find out about the pregnancy after treatment. Often termination of the pregnancy is recommended in these cases. There are new findings that indicate that prior to 10 weeks gestation the fetus does not concentrate iodine and is at relatively little risk. If the RAI occurred after 12 weeks gestation there is an increased risk of hypothyroidism in the infant. More recent studies suggest that such cases can be managed and the infant evaluated for hypothyroidism in utero or after birth.

It is important for you to let your obstetrician know that you have thyroid disease or that you have been treated for thyroid disease in the past. If you have an endocrinologist or family physician who monitors your thyroid levels, bring him/her into the discussion also. The bottom line is that everything works better when we are euthyroid (TSH, T4 and T3 are in normal range).

Go To Page: 1 2

Articles in this Topic    Discussions in this Topic