Pregnancy is a beautiful part of life. However, pregnancy can cause or exacerbate maternal hypothyroidism, also known as hypothyroidism in pregnancy.
Hypothyroidism and pregnancy often go hand in hand. 2-3% of women have high TSH levels before conception, which is a major risk factor for thyroid problems.
18% of pregnant mothers test for the presence of thyroid peroxidase antibody (TPOAb) or thyroglobulin antibody (TgAb). These antibodies are signs thyroid dysfunction may be present.
Hypothyroidism (not including subclinical hypothyroidism) occurs 3-5 times for every 1,000 pregnancies.
Can I have a healthy pregnancy with hypothyroidism? Yes, you can have a healthy pregnancy with hypothyroidism. However, this requires proper management of your condition (probably with thyroid medication) and regular testing and monitoring.
In pregnant women, thyroid disorders may go away after the baby is born without significant treatment.
Let’s take a look at how hypothyroidism and pregnancy interact with one another and what to do about it.
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What is hypothyroidism?
Hypothyroidism is an endocrine condition in which your thyroid gland doesn’t produce enough T3 (triiodothyronine) and/or T4 (thyroxine). It’s also known as underactive thyroid.
Thyroid disease in pregnancy occurs in thousands of women every year. In fact, women are 8 times more likely to develop a thyroid condition than men.
It’s possible to develop maternal hypothyroidism even if you didn’t deal with diagnosed thyroid issues before conception.
Many women have subclinical hypothyroidism even before becoming pregnant, which is marked by elevated TSH (thyroid-stimulating hormone) but T3/T4 levels within range.
Although this is not considered as serious as full-blown hypothyroidism, subclinical hypothyroidism during pregnancy may still cause concerns to both mother and fetus.
Is hypothyroidism considered a factor for high risk pregnancy? Hypothyroidism does not necessarily mean you have a high-risk pregnancy, unless the condition is untreated.
Normal Thyroid Changes in Pregnancy
When you’re pregnant, it’s normal to experience minor fluctuations in thyroid hormone levels and the size of your thyroid.
Two primary hormones produced during pregnancy, estrogen and hCG, can influence thyroid function tests.
Human chorionic gonadotropin (hCG) levels increase in early pregnancy peak around the end of the first trimester. Because hCG can weakly stimulate the thyroid, this may cause a temporarily low TSH result (which should return to normal).
When estrogen is produced, it increases the quantity of thyroid hormone binding proteins, thus increasing overall thyroid hormone levels. However, free T4 levels should remain unchanged.
The thyroid gland may also enlarge during pregnancy. An enlarged thyroid, or goiter, is most common in iron-deficient world regions.
Most women in the United States and other developed countries don’t have a thyroid gland that appears bigger upon physical examination. In many cases, there may be a slight increase (10-15%) seen during an ultrasound.
If your doctor notices a significant goiter, they will likely recommend thyroid function tests.
How does thyroid function impact mother and baby during pregnancy? During the first 18-20 weeks of pregnancy, a fetus does not produce its own thyroid hormone and relies on the mother for it.
About halfway through typical gestation, the baby begins producing thyroid hormones as long as the mother consumes plenty of iodine-rich foods or is taking iodine in their prenatal vitamins. Many women don’t get adequate iodine, so the WHO suggests an iodine supplement of 250 micrograms/day during pregnancy and while breastfeeding.
Symptoms of Hypothyroidism
The symptoms of hypothyroidism in pregnancy are the same as during any other time:
- Weight gain (which is hard to notice during pregnancy)
- Fatigue
- Slow heart rate
- Hoarseness
- Snoring
- Joint pain
- Muscle aches, tenderness, stiffness, and weakness
- High cholesterol
- Cold hands and feet
- Constipation
- Brittle nails
- Thinning hair, eyebrows
- Dry skin
- Impaired memory, trouble concentrating
- Enlarged thyroid (goiter)
Both hypothyroidism and pregnancy can cause chronic fatigue and, of course, weight gain. This is one reason why maternal hypothyroidism, particularly subclinical hypothyroidism in pregnancy, can be hard to identify.
Causes of Hypothyroidism in Pregnancy
Hypothyroidism is a result of the thyroid gland producing too little thyroid hormones.
In primary hypothyroidism, the thyroid gland itself is underactive. 90% of primary hypothyroidism cases stem from Hashimoto’s disease, an autoimmune disorder that is actually reversible in some cases.
Also called Hashimoto’s thyroiditis, this autoimmune thyroid disease causes your own immune system to form antibodies that attack your thyroid. There are two types of antibodies that do this, known as Thyroid Peroxidase Antibodies (TPO antibodies.
Secondary hypothyroidism, which is far less common (about 1 in 1,000 cases), is caused by a malfunctioning pituitary gland, frequently due to a tumor. A malfunctioning pituitary gland which doesn’t produce enough TSH (thyroid-stimulating hormone) leads to hypothyroidism.
Risks of Untreated Hypothyroidism During Pregnancy
For Mother
Hypothyroidism has been linked to pregnancy complications and a number of fertility issues.
Before pregnancy, hypothyroid women may experience heavier than normal menstrual periods. These menstrual changes and serum levels of thyroid-related antibodies and hormones might affect a woman’s fertility.
The good news is that resolving hypothyroidism may lead to successful conception in over ¾ of infertility cases related to an underactive thyroid.
During pregnancy, hypothyroidism can pose a risk to mother and child, including an increased risk of miscarriage. Pregnancy-related complications of maternal hypothyroidism include:
- Anemia
- Higher risk of gestational diabetes
- Gestational hypertension (high blood pressure around 20 weeks of gestation that resolves after delivery)
- Preeclampsia
- Miscarriage
- Placental abruption (when the placenta is separated from the uterine wall before birth)
- Preterm birth
- Postpartum hemorrhage (PPH)
- Heart failure
There are significant risks of miscarriage when TSH levels rise too high. Some sources encourage using a “gestation-specific range” for determining what TSH level is appropriate. This is because TSH usually fluctuates up during the first trimester, on average to 4.0 MoM for single pregnancies and 3.5 MoM for twin pregnancies.
However, high-quality research suggests that TSH levels over 2.5 MoM in the first trimester are associated with significantly increased rates of miscarriage. This is true even when thyroid dysfunction isn’t obviously present.
Interestingly, there isn’t a clear association between low levels of T4 hormones and miscarriage.
Taking these factors into consideration, it is vital for pregnant mothers to maintain a TSH of 0.5-2.5 MoM for the best chance at a healthy pregnancy and birth.
After pregnancy, thyroid problems may still occur. About 8% of women develop a postpartum thyroid disorder (postpartum thyroiditis) within the first year after pregnancy.
Women who are pregnant or breastfeeding should increase their iodine consumption to prevent iodine deficiency. Iodine deficiency can lead to hypothyroidism during or after pregnancy.
According to a 2020 study, hypothyroidism in pregnancy may correlate with an increased BMI (body mass index) for multiple years after giving birth. The good news is that it’s possible to lose weight with hypothyroidism.
What happens if hypothyroidism goes untreated during pregnancy? Untreated maternal hypothyroidism can lead to heart disease, nerve damage, myxedema coma, miscarriage, and (in very rare cases) death.
For Baby
Complications of maternal hypothyroidism for a newborn child, especially when untreated in the mother, can last far into childhood.
The most common risks of untreated hypothyroidism for the baby include:
- Low birth weight
- Stillbirth
- Neonatal death (death shortly after delivery)
- Poor hippocampal development
- Infantile myxedema (a rare disorder associated with severe hypothyroidism that can cause dwarfism, intellectual abnormalities, and other health concerns)
- Poor nervous system development
- Memory problems
- Learning disabilities
- Increased risk of autism
- Issues with visuospatial processing (the ability to interpret what the eyes see)
- Problems with motor skills
- Cyclic vomiting syndrome
- Attention problems, potentially similar to those seen in ADHD
Does hypothyroidism cause birth defects? According to the best evidence available, hypothyroidism in pregnancy does not cause birth defects more often than in a typical pregnancy.
Treatment for Maternal Hypothyroidism
While hypothyroidism in pregnancy can cause serious complications, it’s important to consider the risks of overtreatment and undertreatment when it comes to maternal hypothyroidism.
Who should be treated for hypothyroidism in pregnancy? Women with serum TSH levels greater than 10 mIU/L during the first trimester of pregnancy should be treated for hypothyroidism. When TSH levels are under 2.5 mIU/L, levothyroxine treatment is not required.
If thyroid testing finds a TSH level between 2.5-10 mIU/L, your doctor may prescribe medication to treat your hypothyroidism, especially if you also have TPO or anti-TG antibodies.
Standard treatments for managing maternal hypothyroidism include:
- Increasing thyroid medication dosage
- Following a hypothyroidism diet
- Taking high-quality prenatal vitamins
1. Increasing Dosage of Thyroid Medications
If you develop hypothyroidism after you get pregnant…
Most of the time, maternal hypothyroidism is treated with levothyroxine (the most common prescription thyroid replacement). Levothyroxine is safe to take during pregnancy, if prescribed by your healthcare provider.
Your healthcare provider may recommend dessicated thyroid hormones or synthetic, individualized compounded synthetic medication, rather than levothyroxine, to return maternal thyroid function to normal.
These options may offer a more balanced ratio of T4 and T3 thyroid hormones, rather than just T4 (in the case of traditional levothyroxine).
For patients who did not previously have hypothyroidism, the goal is to resolve normal thyroid function within 30-40 days after you start medication.
If you have hypothyroidism before you get pregnant…
If you are already on thyroid medication, talk to your doctor about adjusting your levothyroxine or medication dosage when you become pregnant or start trying to conceive. If your TSH levels are high, you may need to increase your thyroid medications before you’re able to get pregnant.
When you find out you’re pregnant, be sure to call your doctor right away for a blood test to track your thyroid function. Ideally, you’ll be tested in the first 4-6 weeks of your pregnancy and every 4-8 weeks until you deliver your baby, depending on the stability of your levels.
Many pregnant women already undergoing thyroid hormone replacement require an increased dose (on average, 20-30% more) to maintain healthy levels of TSH. It’s a good idea to test every 4 weeks during the first trimester, and at the beginning of the second and third trimesters, to ensure optimal dosage.
If you develop subclinical hypothyroidism while pregnant…
Treating subclinical hypothyroidism (elevated TSH with normal thyroid hormone levels) with medication is not usually recommended for most patients. However, the American Academy of Endocrinologists (AACE) and American Thyroid Association recommend treating subclinical hypothyroidism during pregnancy with levothyroxine or another type of thyroid medication.
Untreated, subclinical hypothyroidism may increase your risk of miscarriage.
2. Dietary Adjustments
To follow a hypothyroidism diet during pregnancy:
- Eliminate items from your diet that can trigger autoimmune responses, including alcohol, excess sugar, gluten, dairy, soy, artificial sweeteners, and processed foods.
- Fill your plate with nutrient-dense, calorie-rich foods. When possible, opt for organic, whole foods.
- Eat iodine-rich foods like seaweed, eggs, organic grass-fed & fermented dairy, and kelp. As iodine deficiency is a common cause of maternal hypothyroidism, getting plenty of this nutrient will improve your chances for an ideal pregnancy outcome.
In typical hypothyroid patients, our first line approach is to start an autoimmune Paleo diet (also known as AIP diet).
Unfortunately, this isn’t a great idea for pregnant moms — it’s difficult on AIP to get enough calories and nutrition to grow your new human.
If you still struggle with hypothyroidism after delivery, talk to your doctor or dietician about temporarily following an AIP diet to identify your personal dietary triggers.
3. Prenatal Vitamins
It’s essential to take a prenatal vitamin to keep the baby healthy throughout pregnancy (and even before conception!).
Many supplements aren’t known to be safe during pregnancy, including several supplements that we recommend to hypothyroid patients. However, a prenatal vitamin is a must.
Look for a formulation that includes the following:
- Iodine
- Vitamin D3 (try Prime D+K for medical grade, 3rd-party tested Vitamin D)
- Zinc (for medical grade, 3rd-party tested Zinc, see our Prime Zinc)
- Magnesium (we recommend Prime Magnesium)
- Selenium
- B vitamins, especially Methyl-Folate (aka 5MTHF)
- Vitamin K2 (included in Prime D+K)
For the highest quality, medical grade and 3rd-party tested supplements (including Vitamin D3, Zinc, Magnesium and K2) see our online store.
It’s also very important to take high quality Omega-3 fish oils with adequate DHA and EPA along with your prenatal vitamins. These fatty acids are critical for your baby’s brain and nervous system development.
A couple of our favorites are ProOmega 2000 and ProDHA from Nordic Naturals. These can be purchased from the Fullscript store here.
When taking a prenatal supplement containing iron and/or calcium, be sure to leave at least 2-4 hours between taking this vitamin and levothyroxine (or other thyroid medication). These nutrients can interact to impair absorption of thyroid hormones in your gut.
Our favorite Prenatal vitamin is made by Needed. They provide an optimal array of nutrients needed before, during, and after pregnancy.
Their prenatal vitamin comes in a choice of vanilla shake powder or capsules. They supply optimal amounts of methyl-folate, vitamin D, vitamin A, vitamin C, choline, B12, and minerals like zinc, calcium, and magnesium. It does not include iron, which is usually only needed in the 2nd and 3rd trimesters and can be supplemented separately.
With this link, you can get 20% off your first order, or 3 months of a subscription plan.
Who is at risk for maternal hypothyroidism?
Patients at risk for maternal hypothyroidism are those with any of the following risk factors:
- Current treatment of hypothyroidism with levothyroxine, unless the dosage is adjusted prior to conception
- A goiter and/or thyroid nodules
- Over 30 years old
- Pre-existing iodine deficiency
- Past infertility
- Past preterm delivery
- Maternal hypothyroidism during a previous pregnancy
- Previous child with a thyroid disorder
- Family history of thyroid disease (including Graves’ disease or Hashimoto’s) or another autoimmune disorder
- Type 1 diabetes
- Celiac disease
- Levels of certain bacteria in the oral and gut microbiome
- Prior radiation exposure to the neck
- Thyroid cancer
- Previous thyroid surgery
Hypothyroidism Screening During Pregnancy
There are a few tests that your PCP or endocrinology specialist may run if you are at risk for hypothyroidism.
Normal blood tests for hypothyroidism include thyroid-stimulating hormone levels (TSH) and free T4 levels. When TSH levels exceed 2.5 mIU/L during pregnancy, your doctor may prescribe pharmaceutical treatment, especially if TPO antibodies are present. Medication is absolutely recommended when TSH levels exceed 10 mIU/L.
Standard vs. Functional Hypothyroidism Screening
As our understanding of maternal hypothyroidism grows, a more robust set of thyroid function tests may help to paint a fuller picture of your thyroid function.
To screen, diagnose, and treat maternal hypothyroidism, a functional doctor may test your:
- TSH levels
- Free T4
- Free T3
- Total T4 levels
- Total T3
- Reverse T3
- Anti-thyroglobulin and anti-TPO antibodies (Hashimoto’s thyroid antibodies)
- Thyroid-binding globulin (TBG levels)
Who should be screened for hypothyroidism during pregnancy?
Hypothyroidism screening for all women during pregnancy is a controversial topic. However, most obstetrics and endocrinology experts agree that high-risk patients should be screened before conception and/or upon a positive pregnancy test.
We encourage all pregnant women to be screened for underactive thyroid. Around the ninth week of pregnancy is an ideal time for testing thyroid hormone levels. It’s generally recommended that at-risk mothers are tested every 4 weeks during the first half of pregnancy.
In general, women who have risk factors for maternal hypothyroidism should certainly be screened when they become pregnant.
You may also be tested for hyperthyroidism (overactive thyroid), as a few symptoms can overlap. Overtreatment of hyperthyroidism can lead to an underactive thyroid.
Ultimately, we encourage every individual to seek out an individualized diagnosis plan, especially when pregnant. Blood tests should not interfere with your pregnancy, but they may cause discomfort at the vein puncture site.
Getting Pregnant With Hypothyroidism
Trying to conceive with hypothyroidism can be difficult for both women and men.
In women, hypothyroidism can prevent ovulation, shorten the second half of the menstrual cycle, and make it more difficult for an embryo to develop. In men, hypothyroidism interferes with sperm production and can decrease libido.
While you’re trying to get pregnant, you should have your thyroid hormone levels checked regularly and follow up with your doctor as soon as you have a positive pregnancy test.
If you test positive for TPO antibodies before pregnancy, selenium supplementation may help you avoid developing hypothyroidism during pregnancy.
Postnatal Treatment for Hypothyroidism
If you developed hypothyroidism after getting pregnant, you may be able to discontinue taking thyroid medication once your baby is delivered.
If you already had hypothyroidism before conceiving, you’ll likely be able to go back to your pre-pregnancy dosage of thyroid medication based on postnatal TSH levels. However, always follow your doctor’s orders — in some cases, your TSH won’t regulate until after you’re finished breastfeeding.
Children of people who develop maternal hypothyroidism are somewhat more likely to develop thyroid dysfunction later in life. Prepare them for the possibility when the time comes, and keep their iodine consumption at a normal level.
You should continue consuming 250 micrograms or more of iron each day while breastfeeding.
Can I breastfeed with hypothyroidism? Yes, breastfeeding with hypothyroidism is safe and recommended for both mother and baby. Talk to your doctor if you’re concerned about any risks of breastfeeding and an underactive thyroid.
Newborn babies are susceptible to underactive thyroid. Fortunately, all 50 US states require universal screenings for hypothyroidism at birth. If newborns are left untreated, congenital hypothyroidism can lead to slow brain development.
Hypothyroidism in pregnancy should be closely monitored, but proper treatment can allow you to have a healthy pregnancy and birth.
To schedule a FREE in-person consultation with a member of our medical staff, schedule your appointment today.
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