Thyroid Health in Pregnancy and Post-Partum


For momma: helps avoid extra fatigue, constipation and weight gain as well as postpartum depression and low milk supply

For baby: developing babies depend on momma’s thyroid hormones for the first 20 weeks of gestation!

Hypothyroidism in pregnancy can have some pretty scary outcomes including fetal death, maternal hypertension, preterm birth, breech delivery and low birth weight. For this reason, I take it very seriously. I recommend all newly pregnant mommas have a full thyroid panel in the first trimester. For all mommas with preexisting hypothyroidism, I monitor levels every 2-4 weeks during pregnancy and for the first 3-6 months postpartum.



  1. Estrogen increases the production of thyroid binding proteins, making the free, active hormone less bioavailable. 
  2. The placenta increases the breakdown of both T4 and T3.
  3. Increased maternal blood volume dilutes thyroid hormones.
  4. Increased maternal kidney filtration results in more iodine loss, an essential nutrient for thyroid function.



TSH: A hormone produced in the brain that tells the thyroid to produce T4, elevated in hypothyroidism

T4: Thyroid hormone released by the thyroid gland

T3: Made from T4 in your tissues, the most active thyroid hormone

Simply measuring TSH is not enough in pregnancy. The hormone HCG, produced by the placenta, will partially suppress TSH. For this reason, we need to look at a complete thyroid panel that includes not only TSH, but free T4 and free T3 as well. 




Very little T3 crosses the placenta and so offering both T4 and T3 could lower the amount of T4 that baby receives. As a general practice, T4 alone is my choice in pregnancy, with some exceptions. If momma is stable on combination therapy before she becomes pregnant and numbers remain stable during pregnancy, it is ok to continue. 

If free T3 is suboptimal, we focus on improving T4 to T3 conversion with therapies such as nutrients, reducing stress and limiting inflammatory foods. 


Thyroid hormone production and metabolism depends on iodine, selenium, zinc, vitamin D and iron. All pregnant mommas should evaluate the amounts of these nutrients in the prenatal. If the prenatal is offering much lower doses, discuss additional sources from food or supplements with your doctor if indicated. Note, most of these are maximum daily levels.

  • Iodine: 225mcg
  • Selenium: 100-200mcg 
  • Zinc: 15-25mg 
  • Vitamin D: 1,000-5,000IU 
  • Iron: dose based on lab values


Thanks for reading! Give us a call to get your thyroid labs drawn if you’re in early pregnancy, breast-feeding or thinking about conceiving. We’re here to support you!