How Does Hypothyroidism Affect Pregnancy?

Your thyroid gland controls many functions in your body. Years ago, we called this gland the “master” gland because it controls so many functions throughout your body. These functions include staying warm, using energy wisely, and keeping the brain, heart, and other muscles working and most other organs as well.

Think of your thyroid gland as a furnace. Think of thyroid stimulating hormone (TSH) as the thermostat calling for heat from your furnace. The product of the furnace is heat, while the products of the thyroid gland, free T3 and free T4, provide the heat the TSH calls for. During pregnancy, we measure free T3 and free T4. The standard tests for T3 and T4 will be falsely elevated because when you are pregnant, the high levels of HCG (human chorionic gonadotropin) and estrogen will cause additional proteins to bind to the T3 and T4. This binding of protein to the T3 and T4 makes these hormones falesely elevated. In pregnancy, then, there is a need to test for free T3 and free T4, the hormone levels which have no protein bound to them.

Up Until 18 to 20 Weeks, Babies Depend Upon Mother’s Thyroid Gland

For the first 18 to 20 weeks of pregnancy, your baby’s thyroid gland doesn’t work so your baby is very dependent on your thyroid gland and thyroid hormones which cross the placenta. If mom is hypothyroid (too little thyroid hormones), it is very important for her to have her TSH, free T4, and free T3 tested and retested with necessary medication adjustments.

What Are the Risk to the Baby When Mother is Hypothyroid?

The specific risks for the baby in the womb of a mother who is hypothyroid, either untreated or undertreated, includes diminished brain development, which manifests as low intelligence, neurological delay, developmental delay, preterm birth, small size for age, and stillbirth. In other words, the baby’s development and health will be less for each stage of pregnancy than it would have been with normal thyroid status.

Mothers who have already been diagnosed with hypothyroidism need to be treated in pregnancy. For mothers who have not been diagnosed with hypothyroidism, this question is harder to answer then you might expect. Testing mother’s blood for thyroid hormones is not done routinely.

A TSH value greater than 10 is sometimes used to establish the need for hormone replacement. With a value of 10, your TSH thermostat would be calling for heat, but the furnace would not run and your house would be getting cold. I would recommend keeping all the values for free T4, free T3, and TSH within normal limits during pregnancy. The consequences of hypothyroidism for the baby in the uterus are extreme.

Do I Need Iron Supplements When I’m Pregnant?

When the baby in the womb begins to make its own thyroid hormones at about 20 weeks, halfway through a normal pregnancy, it still remains dependent on its mother for the iodine it needs to make its own thyroid hormone. Because iodine intake in this country is low, the American Thyroid Association recommends pregnant women take 150 micrograms iodine by mouth per day.

How much iron does a pregnant woman need?

Iron is needed for your body to produce hemoglobin. Non-pregnant women need about 18 mg of iron per day, but pregnant women require much more because their bodies need to produce more blood because of their uterus expansion and the baby. It is recommended that pregnant women take 27 mg of iron daily. This is the amount of iron found in most premium vitamins, but check your prenatal vitamin label to see how many milligrams of iron are included in your daily dose.

Vitamin C, especially from plant sources such as oranges, grapefruit, kiwi, broccoli, peppers, strawberries, and watermelon, can help your body absorb iron.

Can Eating Calcium Interfere with Absorbing Iron?

Calcium and iron are both positively charged ions with two bonds tied together, commonly termed covalent. Therefore, both calcium and iron compete in the body for absorption sites. Prenatal vitamins probably contain both calcium and iron. Read your prenatal vitamin label. If calcium and iron are together in your prenatal vitamin, I suggest you might try taking iron supplements separately. In addition, when eating, consider eating high calcium foods as far away from as possible from your meals with high iron content.