Learn about the thyroid, pregnancy and infancy

Things Every Mother Should Know

Importance of adequate iodine intake in pregnancy

Thyroid hormone is necessary for normal brain development. In early pregnancy, babies get thyroid hormone from their mothers. Later on as the baby’s thyroid develops it makes its own thyroid hormone. An adequate amount of iodine is needed to produce fetal and maternal thyroid hormone. The best way to ensure adequate amounts of iodine reach the unborn child is for the mother to take a prenatal vitamin with a sufficient amount of iodine. Not all prenatal vitamins contain iodine, so be sure to check labels properly.

Hyperthyroidism & pregnancy

Hyperthyroidism, if untreated, can lead to stillbirth, premature birth, or low birth weight for the baby. Sometimes it leads to fetal tachycardia, which is an abnormally fast pulse in the fetus. Women with Graves’ disease have antibodies that stimulate their thyroid gland. These antibodies can cross the placenta and stimulate a baby’s thyroid gland. If antibody levels are high enough, the baby could develop fetal hyperthyroidism, or neonatal hyperthyroidism.

A woman with hyperthyroidism while pregnant puts her at an increased risk for experiencing any of the signs and symptoms of hyperthyroidism. And unless the condition is mild, if it is not treated promptly a woman could miscarry during the first trimester; develop congestive heart failure, preeclampsia, or anemia; and, rarely, develop a severe form of hyperthyroidism called thyroid storm, which can be life threatening.

Hypothyroidism & pregnancy

Thyroid hormone is critical for the brain development of a fetus, because it depends solely on its mother for its thyroid hormone for most of the first trimester of pregnancy. When deprived of thyroid hormone, a baby is at an increased risk for neural development, which may lead to mental retardation.

Most women who develop hypothyroidism during pregnancy have mild disease and may experience only mild symptoms or sometimes no symptoms. However, having a mild, undiagnosed condition before becoming pregnant may worsen a woman’s condition. A range of signs and symptoms may be experienced, but it is important to be aware that these can be easily written off as normal features of pregnancy. Untreated hypothyroidism, even a mild version, may contribute to pregnancy complications. Treatment with sufficient amounts of thyroid hormone replacement significantly reduces the risk for developing pregnancy complications associated with hypothyroidism.

Miscarriage and thyroid disorders

A woman with untreated hypothyroidism is at the greatest risk for a miscarriage during her first trimester. Unless the case is mild, women with untreated hyperthyroidism may miscarry during the first trimester.

Care of a child with congenital hypothyroidism

All newborns in the United States are routinely tested for congenital hypothyroidism. Children with this condition are deficient in thyroid hormone, which is critical for the development of the nervous system. Untreated, congenital hypothyroidism can lead to mental retardation and stunted growth. Thanks to testing, every child born with congenital hypothyroidism is promptly treated with thyroid hormone, allowing them to develop normally and go on to live a normal, healthy life.

For those taking thyroid hormone, what to do before becoming pregnant

How much and which thyroid hormone to take before conception 

Levothyroxine sodium pills are completely safe for use during pregnancy. They are prescribed in dosages aimed at replacing the thyroid hormone the thyroid isn’t making. Once a woman begins taking this medication, she will be monitored to ensure TSH levels have normalized. After normalization, a doctor will want to check these levels every six to eight weeks until normalization and less frequently thereafter. They may also counsel women to take thyroid hormone pills at least one-half hour to one hour before or at least three hours after taking iron-containing prenatal vitamins or calcium supplements, which can interfere with the absorption of thyroid hormone.

High levels of thyroxine (T4) appear to be required for normal brain development early in the pregnancy. A combination of T4 and T3 (triodothyronine) as well as desiccated thyroid hormone do not provide an adequate amount of T4 and therefore should be avoided in a woman planning pregnancy or a woman that is already pregnant.

How to achieve and maintain excellent control throughout pregnancy

For a woman being treated for hypothyroidism, it’s imperative to have her thyroid checked as soon as the pregnancy is detected so that medication levels may be adjusted. TSH levels may be checked one to two weeks after the initial dose adjustment to be sure it’s normalizing. Once the TSH levels drop, less frequent check-ups are necessary during the pregnancy they tend to stabilize by the middle of pregnancy. Although thyroid hormone requirements are likely to increase throughout the pregnancy they tend to eventually stabilize by the middle of pregnancy. The goal is to keep TSH levels within normal ranges which are somewhat different than proper levels in a non-pregnant woman. After giving birth, the doctor should adjust dosage to the preconception level.

Role of the endocrinologist

An endocrinologist is a physician or medical scientist who researches and treats patients with diseases relating to the endocrine system. Their advanced and specialized training make them experts in the care of endocrine disease, such as thyroid disorders.