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Are you currently being treated for a thyroid condition or you have thyroid nodules or a goiter? Have you had a thyroid condition in the past? Do you have an autoimmune disorder or a family history of thyroid autoimmune disease, like Graves’ disease or Hashimoto’s disease? What if you’ve had high-dose neck radiation or treatment for hyperthyroidism?
If you answered “yes” to any of these questions and are starting to think about having kids (or even if you’re just curious), read on.
The thyroid gland plays a very important role in your reproductive health, and you may have many questions about your fertility and your current medications. The butterfly-shaped gland does, after all, lead to issues for 1 in 8 people with ovaries. Ultimately, your best chance at conceiving and having a healthy pregnancy is when your condition is properly managed and treated.
First things first: Can you get pregnant with a thyroid condition?
Absolutely — but hyperthyroidism (an overactive thyroid gland) and hypothyroidism (an underactive thyroid gland) can have a negative effect on fertility and make conception more challenging. That’s because both conditions have been linked to irregular menstrual cycles. When cycles are irregular, timing sex or insemination around the days you’re most likely to get pregnant can be difficult.
If you already know you have a pre-existing thyroid condition, you have a major advantage over the many people who are undiagnosed: Treating your thyroid condition before trying to conceive can help you reduce the likelihood of fertility issues. In one study of a group of almost 400 women dealing with infertility, 24% of participants were found to have hypothyroidism — but within a year of treatment, 76% were able to conceive.
Below, we’re providing an overview of what to keep in mind before, during, and after pregnancy if you have a pre-existing thyroid condition.
What’s important to do and know before trying to get pregnant?
While, like we mentioned above, getting pregnant is definitely possible if you have a thyroid condition, there are a few things to understand before you start trying to conceive.
1. Talk to your healthcare provider about your plans for kids.
“Thyroid hormones are important for your general health, but we also know that pregnancy can be impacted by thyroid problems if those problems aren’t addressed first,” explained Dr. Nataki Douglas, MD, PhD, a reproductive endocrinologist and the chair of the Modern Fertility Medical Advisory Board, in a virtual Q&A on trying to get pregnant.
In most cases, thyroid disorders are diagnosed by your primary care provider or an endocrinologist — a specialist who treats hormone problems like thyroid disease. Chances are you’re already under the care of one of these doctors, so let them know you’re in the process of planning for kids and they can help you manage your thyroid disorder before conception to avoid fertility-related issues down the line.
If you’ve had thyroid cancer and received radioactive iodine (RAI) doses to ensure the stability of your thyroid function and confirm remission of thyroid cancer, the Endocrine Society recommends avoiding pregnancy for six months to one year.
2. Stay on top of your thyroid-stimulating hormone (TSH) levels.
Thyroid-stimulating hormone (TSH), the hormone made in the pituitary gland, tells your thyroid how much T4 and T3 to make. By this time, you may already be accustomed to having regular blood tests to test your thyroid levels and know the following info:
- A high TSH level usually indicates hypothyroidism: Your thyroid gland is underactive and not responding to the signal from the pituitary gland to make thyroid hormones, so the TSH is extra high, while the thyroid hormones are low.
- A low TSH level usually indicates hyperthyroidism: Your thyroid gland is overactive and the extra thyroid hormone is inhibiting production of thyroid stimulating hormone. The TSH is low while the thyroid levels are typically high.
The Endocrine Society recommends “all women considering pregnancy with known thyroid dysfunction should be tested for abnormal TSH concentrations before pregnancy” and that TSH should be below 2.5 mIU/mL during the first trimester. “Normal” TSH values can range depending on the lab used, but they’re typically between 0.4 and 4.5 mIU/L. However, a study of nonpregnant women taking thyroid medications showed over 40% were not even in the normal range and were either hypo- or hyperthyroid — baring the case to check your TSH levels regularly even when on medication.
3. Do not stop your current thyroid medication without talking with your doctor.
Many people worry about the effects of medication on their developing fetus, but the benefits of taking the thyroid medicines your doctor prescribes greatly outweigh the risks to both the birthing parent and the fetus. “Being compliant with thyroid disorder treatment and monitoring is an essential component to fertility and important for a successful pregnancy,” says Dr. Nadiyah Chaudhary, PharmD, BCPS, a pharmacist who works closely with the reproductive endocrinologist care teams at the University of Chicago Medicine to assist in medication management.
If hyperthyroidism is left untreated with medicine during pregnancy, that can lead to:
- Increased risk of premature birth
- Increased risk of preeclampsia
- Increased risk of thyroid storm (sudden, severe worsening of symptoms)
- Increased risk of a fast heart rate in the newborn
- Increased risk of low birth weight
- Increased risk of miscarriage
If hypothyroidism is left untreated with medicine during pregnancy, that can lead to:
- Increased risk of anemia
- Increased risk of preeclampsia
- Increased risk of low birth weight
- Increased risk of miscarriage
- Increased risk of stillbirth
- Problems with fetal growth and brain development
4. Learn about how your thyroid hormones will change with pregnancy.
With any pregnancy comes a rise in hormones, but two of them — human chorionic gonadotropin (hCG) and estrogen — can trigger a temporary rise in thyroid hormone levels in your blood.
Thyroid hormone levels naturally change throughout pregnancy due to normal physiological changes. For this reason, Dr. Chaudhary explains, “There are trimester-specific ranges used to interpret lab values of thyroid function tests.” In the first trimester, for example, the normal TSH range is less than 2.5 mIU/L as levels between 2.5 and 5.0 are associated with increased pregnancy loss.
Here’s how thyroid hormones may change during pregnancy:
- High levels of hCG in the first trimester could result in slightly low TSH before going back to normal later on in the pregnancy.
- Estrogen may increase the total thyroid hormone levels — but the thyroid gland may still be functioning normally as long as TSH and fT4 levels are within range for that specific trimester.
Aside from thyroid hormone levels, the thyroid gland may also become larger during pregnancy — but this happens more frequently in iodine-deficient areas than it does in the US.
5. Monitor your iodine nutrition before and during pregnancy.
Iodine is a key nutrient for thyroid hormones and thyroid health.* During pregnancy and lactation (whether or not you’re breastfeeding/chestfeeding), iodine requirements from the US Food and Drug Administration increase from 150 for nonpregnant people micrograms (mcg) to 290 mcg.
That said, supplemental iodine — which is a common component of prenatal vitamins — may not be recommended if you’re taking levothyroxine (LT4), also known as L-thyroxine, a manufactured form of the thyroid hormone thyroxine (T4). Since prenatal vitamins are an essential part of preconception and pregnancy nutrition, it’s important to talk to your healthcare provider about whether or not a prenatal vitamin with iodine is right for you.
What’s important to do and know during pregnancy?
Here’s what you can expect once you’re actually pregnant and have a thyroid condition.
1. Be prepared for your current medication regime to change.
Once someone with a pre-existing thyroid condition becomes pregnant, the Endocrine Society has guidelines for doctors to follow when it comes to adjustments in thyroid medication during pregnancy:
- If you had hyperthyroidism (overactive thyroid) before getting pregnant, your healthcare provider may prescribe antithyroid medicines called propylthiouracil in the first trimester and change to medications called methimazole in the second and third trimesters. The timing of these medications is important to reduce the risk of liver problems and birth defects.
- If you had hypothyroidism (underactive thyroid) before getting pregnant, you may need to increase your medication dosage and/or change to a new medication. Levothyroxine is the most common medicine used to treat hypothyroidism during pregnancy. It’s safe to take this medicine during pregnancy.
If all of these changes seem a little overwhelming, specialists like Dr. Chaudhary are here to support you by helping you do the following things:
- Obtain insurance approval for your new medications.
- Enroll in financial assistance programs.
- Coordinate delivery of your medications.
- Get counsel on your new medication regimen.
2. Expect more thyroid monitoring during pregnancy.
The general population of pregnant people doesn’t receive screening for thyroid dysfunction. However, for those with a personal history of thyroid disorders, the American College of Obstetricians and Gynecology (ACOG), the Society for Maternal-Fetal Medicine (SMFM), and the Endocrine Society clinical practice guidelines recommend screening.
3. Always be your own advocate.
Because providers may differ in their screening practices, it’s important to be your own advocate on this from the very beginning. Always share your thyroid health history at your very first prenatal appointment. Experts say testing for serum TSH abnormalities should be done by your ninth week of pregnancy or at the time of your first visit.
What’s important to do and know after giving birth?
After your delivery, keep tabs on these aspects of both your own and your newborn’s health.
1. You may need to return to your pre-pregnancy medication dosage.
Most people with hypothyroidism, for example, need to decrease the levothyroxine (Synthroid) dosage they received during pregnancy to the pre-pregnancy dose after delivery.
Both antithyroid and thyroid replacement medicines (like Synthroid) are safe to take at low doses while you’re breastfeeding/chestfeeding.
2. If you have Graves’ disease, your newborn may be evaluated for thyroid dysfunction and treated (if necessary).
This is because the thyroid receptor antibodies that cross the placenta during pregnancy can affect the fetus. The recommendation is to test the birthing parents’ antibody levels at 22 weeks gestation if you have current or past Graves’ disease. After delivery, testing the infant for thyroid disease (and treating them if necessary) is recommended.
3. Unusual signs or symptoms after delivery may indicate thyroid complications.
Some thyroid complications can occur postpartum. People with a history of thyroid problems are at an increased risk of postpartum thyroiditis, a condition that occurs in about 5%-10% of people with ovaries when the thyroid becomes inflamed after having a baby. It may first cause the thyroid to be overactive, but it can eventually lead to an underactive thyroid.
However you’re measuring TSH levels, it’s always important to talk to your healthcare provider about how to best monitor your thyroid health as you go after your fertility goals, move through your pregnancy, and navigate new parenthood.
This article was reviewed by Dr. Jennifer Conti, MD, MS, MSc.
* This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Dr. Jenn Conti is an OB-GYN and serves as an adjunct clinical assistant professor at Stanford University School of Medicine.