Hypothyroidism and Pregnancy

Pregnancy causes major changes in the levels of thyroid hormones. That’s why; thyroid problems sometimes can start or get worse during pregnancy. Hypothyroidism or underactive thyroid means body makes less amount of thyroid hormone than required. With routine screening, hypothyroidism is now increasingly being diagnosed during pregnancy.

Untreated hypothyroidism in mother poses a risk for both mother and baby. A pregnant woman's thyroid hormones are vital not only for her but also for the mental development of her baby. Pregnant women with uncontrolled hypothyroidism are at increased risk of developing high blood pressure, anaemia (low haemoglobin), miscarriage, premature birth (before 37 weeks of pregnancy), or even stillbirth. Also there may be risk of mental retardation in baby if mother had untreated hypothyroidism during pregnancy. In a landmark observational study it was found that women with untreated hypothyroidism deliver babies with an average intelligence quotient (IQ) score 7 points below the mean IQ of children born to healthy women.

Most common cause of hypothyroidism during pregnancy is Hashimoto's disease, which is an autoimmune disease. Women who are above age 30 have high risk for developing hypothyroidism; similarly other risk factors for developing hypothyroidism are-past infertility or preterm delivery, family history of thyroid or other autoimmune disease, type 1 diabetes or other autoimmune disease, prior radiation treatment of the head or neck, past thyroid surgery, women who have thyroid antibodies, mainly thyroid peroxidase (TPO) antibodies, or goitre (swelling of the thyroid gland). A pregnant woman's thyroid hormones are vital for her and for the healthy development of her baby.

To detect hypothyroidism, your doctor does a physical exam and orders blood tests to measure your thyroid hormone levels. High TSH levels plus low levels of T4 indicate hypothyroidism. High TSH levels but normal levels of T4 are signs of subclinical (early or mild) hypothyroidism. In our opinion all pregnant women should have a thyroid function test even if they do not have symptoms of an underactive thyroid. Ideally, this screening blood test should take place at the first prenatal visit.

The treatment for hypothyroidism is thyroid hormone replacement with a synthetic levothyroxine. This drug is the same as the T4 your body makes and is safe for pregnant women. Ladies with hypothyroidism during pregnancy should be referred to Endocrinologist for proper evaluation/management.

Before pregnancy. It is important that thyroid hormone levels are normal both before and during pregnancy. If you are already receiving levothyroxine to treat hypothyroidism, you should have your thyroid hormone levels checked before you try to conceive. If your TSH levels are too high, you may need an increase in your dose of levothyroxine. You should delay pregnancy until your disease is well controlled. Current guidelines say that your TSH should be less than 2.5 mIU/L, before you plan pregnancy.

During pregnancy. Once a hypothyroid woman becomes pregnant, the levothyroxine dose often must increase. Possibly the dose must go up by as much as 30% or more in the first 4 to 6 weeks of pregnancy. Contact your Endocrinologist soon after you know you are pregnant, so you can get a thyroid function blood test and discuss your treatment plan.

If you receive a new diagnosis of hypothyroidism during pregnancy, you will need your T4 levels brought to normal as quickly as possible. Your doctor may give you increasing doses of levothyroxine until your T4 levels become normal. About 30 to 40 days after you start treatment, you should have your thyroid function retested. Even subclinical or mild form of hypothyroidism deserves treatment during pregnancy.

It is also important that you don’t take calcium and iron tablets (routinely prescribed during pregnancy) at the same time with levothyroxine. Iron/calcium tablets can interfere with the absorption of thyroid hormone. Take these tablets at least 4 or 6 hours after taking your levothyroxine.

After pregnancy- After delivery, most hypothyroid women need to decrease the levothyroxine dose they received during pregnancy.Bottom of Form