Hypothyroidism and Pregnancy

What to do if you're hypothyroid and pregnant.

Doctor checking pregnant woman
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What is hypothyroidism?

Thyroid disease is something that you may have suffered from prior to your pregnancy. Hypothyroidism is defined as an underactive thyroid. This can be from surgical removal, disease or a congenital issue with your thyroid. You may have been diagnosed during some routine blood work or because of symptoms or complications. You may find out before your are pregnant at your preconceptional health care or in early pregnancy if your practitioner screens.

Screening for Hypothyroidism in Pregnancy

There is not universal screening for hypothyroidism in pregnancy. If you are concerned about your thyroid because of a family history, symptoms or other reasons, be sure to ask your practitioner for a simple blood test to screen for your thyroid stimulating hormone (TSH) levels and your free T4 (thyroxine) levels.

How can hypothyroidism harm my pregnancy or baby?

About 2 out of 1,000 pregnancies will be complicated by clinical hypothyroidism and another approximately 2% of pregnancies suffer from subclinical hypothyroidism. The biggest risk is that when a mother has an elevated TSH level, there is an increased risk of your baby have poor intellectual development and a lowered IQ.

Some women with overt hypothyroidism will also suffer from infertility. If this is the case, you may also be at risk for other complications including placental abruption, premature birth, stillbirth and other complications.

Talk to your practitioner about your specific risks. Though, in general, if your thyroid levels are within normal limits before pregnancy, your risks are greatly reduced. This is why it is important to talk to your practitioner prior to getting pregnant.

How is hypothyroidism treated in pregnancy?

Typically you will need to have your thyroid levels checked every 4-6 weeks during your pregnancy.

Many women find that they will need to adjust their replacement thyroxine upwards in pregnancy. Though this is not necessarily true for everyone. Your physician or midwife will increase your dose by 25-50 mcg until you are within normal limits.

Postpartum will be another time to watch your levels because you will most likely need to adjust your medications after you have your baby. This can happen over the course of a few weeks to months and is not necessarily apparent right away.

Will thyroid medications harm my baby?

Thyroid medications are considered very safe for pregnancy and breastfeeding. Though they may need to be adjusted regularly in pregnancy and postpartum. This may mean having your blood work done more often than when you aren't pregnant.

Will hypothyroidism affect my labor?

You should notice no changes in how you give birth when you have thyroid disease.

Will my baby be hypothyroid?

There is no way to know without testing your baby. There is newborn screening for congenital hypothyroidism in every state.

Your baby will be tested within a few days of birth. There will be follow up if the results are inconclusive or if the baby tests positive.

Source:

Bryant SN, Nelson DB, McIntire DD, Casey BM, Cunningham FG. An analysis of population-based prenatal screening for overt hypothyroidism. Am J Obstet Gynecol. 2015 Oct;213(4):565.e1-6. doi: 10.1016/j.ajog.2015.06.061. Epub 2015 Jul 8.

Patton PE, Samuels MH, Trinidad R, Caughey AB. Obstet Gynecol Surv. 2014 Jun;69(6):346-58. doi: 10.1097/OGX.0000000000000075. Controversies in the management of hypothyroidism during pregnancy.

Williams Manual of Obstetrics: Pregnancy Complications. 22nd Edition. McGraw-Hill. 2007.

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