Thyroid and Pregnancy: What You Need to Know

Everything you Need to Know About Your Thyroid and Pregnancy

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Pregnancy alters what is considered “normal thyroid function” in the body. 

The changes that occur during pregnancy are, therefore, very important to understand if you have thyroid disease (or suspect you do). 

This guide will walk you through everything you need to know about your thyroid and pregnancy including symptoms that indicate you might have thyroid disease, how to manage thyroid medication during pregnancy and what thyroid antibody positivity means

Let’s jump in: 

Does Pregnancy Cause Thyroid Disease?

If you are pregnant or planning on getting pregnant, then there are a few things you need to understand about your thyroid and how it may impact your pregnancy and child.

Your thyroid function is critical to the development of your child.

Why?

Because, in the beginning, your child is dependent upon your thyroid function until it can start to produce its own thyroid hormone.

It’s also been shown that hypothyroidism during pregnancy, even by a small amount, may result in developmental issues including a lower IQ in your child (1) if it is not treated appropriately. 

For these reasons, it’s absolutely critical that you have an understanding of how thyroid disease may present in pregnancy, how to identify if you are having issues and how to go into pregnancy with expectations if you have existing thyroid disease.

Because thyroid disease is actually quite common among pregnant women, many women ask the question:

Does pregnancy cause thyroid disease?

The answer is that pregnancy probably does not cause thyroid disease by itself, but rather it sets a situation up in which existing thyroid disease is exacerbated.

It’s not uncommon for some women (and men) to have low-grade thyroid disease, known as sub-clinical hypothyroidism, which isn’t identified or treated.

This type of thyroid disease may be the result of inflammatory diseases, obesity (2), existing autoimmune disease, or nutrient deficiencies.

So, because pregnancy puts increased metabolic demand on the body (3), it may be that small and existing thyroid disease is more pronounced during pregnancy (and after).

So it’s not that pregnancy leads to thyroid disease so much as it reveals existing thyroid problems.

Now it’s certainly possible to develop thyroid disease WHILE you are pregnant as well, but this may be less common when compared to women who start with existing thyroid disease.

So how do you know if you have thyroid disease?

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How to Identify Thyroid Symptoms During Pregnancy

Luckily, because thyroid function is so critical for the development of your baby testing for thyroid function is considered standard operating procedure once you are found to be pregnant.

So your doctor should automatically assess your TSH during your first set of routine blood tests.

But is this testing enough?

It turns out, and we will talk about this more below, that certain changes occur in pregnant women which makes standard thyroid testing less valuable when compared to other tests.

But in addition to testing, you also want to familiarize yourself with the symptoms of thyroid disease.

Why?

Because these symptoms are often the first sign of trouble (lab tests tend to follow) when it comes to your thyroid.

The problem is that some of the general symptoms of thyroid disease may tend to mimic “standard pregnancy symptoms”.

Often thyroid symptoms tend to be more exaggerated when compared to pregnancy symptoms, and with the addition of lab tests, you should be able to easily identify the issues.

So how do thyroid symptoms manifest in pregnancy?

You want to be familiar with both hyperthyroid (too much) and hypothyroid (too little) symptoms.

Symptoms of hypothyroidism (meaning too little thyroid hormone) include:

  • Excessive fatigue
  • Excessive hair loss
  • Rapid weight gain (more than what is expected)
  • Cold extremities and intolerance to cold temperatures (you find yourself wearing sweaters in the summer or wearing socks to bed)
  • Very dry skin
  • Memory issues or difficulty concentrating
  • Slow fetal growth

As you can see, many of these symptoms may mimic normal pregnancy symptoms but you can usually separate the pathologic symptoms because they tend to be more profound and excessive compared to whatever your baseline is.

So if your fatigue is normally a 4/10 on a scale, you might find it jumps up to 7/10 out of the blue and stays there.

Symptoms of hyperthyroidism (meaning too much thyroid hormone) include:

  • ​​Rapid heart rate or heart palpitations
  • Difficulty breathing or shortness of breath
  • Tremors in the hands
  • Insomnia or difficulty sleeping
  • Weight loss or slower than normal weight gain
  • Slow fetal growth

If you are experiencing any of these symptoms then you should have your thyroid lab tests evaluated as soon as possible.

Don’t be afraid to speak up about your existing symptoms.

Even if they show up negative you will have peace of mind knowing that your baby is safe.

The worst thing you could do is to ignore these warning signs and potentially put your baby in harm’s way.

Pregnancy increases Thyroid Hormone Requirements (Why you need to increase your dose during pregnancy)

Another very important point to understand is that the demand for thyroid hormone increases during pregnancy.

What do I mean?

I mean that whatever amount of thyroid hormone that your body produces naturally when it is healthy is INCREASED when you are pregnant.

Now, this isn’t normally an issue for women with a healthy thyroid gland, but what about women who are taking thyroid hormone?

What you may not realize is that when you are taking thyroid hormone you are effectively shutting down the natural ability of your thyroid gland to produce thyroid hormone.

So you are dependent upon the DOSE of thyroid hormone that you are currently taking.

This means that if you are taking thyroid hormone and you become pregnant you will need to have your thyroid dose adjusted.

And for most women, this means INCREASING your dose (not decreasing).

This change in dosing should occur as soon as possible as well.

The increase in demand for thyroid hormone comes because your baby has a demand for thyroid hormone.

So the amount that you normally take is only sufficient for your body, and it doesn’t take into account the need of your baby.

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But how much more thyroid hormone will you need when you become pregnant?

The answer is that it depends on the person, but studies show that on average your dose may need to be increased anywhere by 40% to 100% (4).

So this means that if you are taking 50mcg of T4 (Synthroid or levothyroxine) you may need to increase your dose up to 75mcg (50% increase) to 100mcg (100% increase).

And, again, this increase in your dose is absolutely necessary because your thyroid may not be able to naturally increase the amount of hormone necessary for your child

This also means that increasing your dose as soon as possible is of utmost importance (preferably during the first trimester after initial labs have been drawn). 

Pregnancy Increases Iodine Demand (Which means you need more Iodine)

Remember when we were talking about thyroid disease potentially revealing existing thyroid issues?

Well, part of this issue may come from iodine usage and demand during pregnancy.

To help illustrate this point we can look at basic studies which outline the demands of iodine uptake and usage for normal men and women.

We know that men and women need around ~150mcg of iodine per day to keep up with the demand for thyroid hormone production in the body (5).

Most of this iodine must come from your diet such as iodinated salt or from sea vegetables.

But we also know that pregnant women, and lactating women, need up to 290mcg of Iodine per day (6).

We also know that the average consumption of iodine per day is around 130mcg (7).

Do you see the problem?

On average we are consuming barely enough to meet the demands of normal day to day thyroid needs, but when you throw it pregnancy and lactation the consumption of iodine may be insufficient.

Because of this, most prenatals do contain extra iodine, such as this one.

But the amount of iodine in most prenatals is usually around 100-150mcg per day.

If you are consuming the regular amount of 150mcg from food sources then the added 150mcg of Iodine from your prenatal is probably sufficient.

The key here is to be mindful that more factors are involved in thyroid function during pregnancy so be aware of the foods that you consume and make sure to check for iodine in your prenatal vitamin.

If you have a history of thyroid disease or suspect that you have an increased risk for developing thyroid disease during pregnancy, it may be wise to avoid goitrogenic foods (8) (those foods that reduce thyroid function) and increase your consumption of sea-vegetables (natural iodine foods). 

It’s also important to continue this supplementation of Iodine through lactation if you are breastfeeding

This mismatch of Iodine intake and demand may be enough to manifest slight hypothyroid symptoms in your body (please see the symptom list above).

Thyroid Antibodies and Pregnancy – Is it Hashimoto’s or something else? 

It’s important to remember that pregnancy is a condition which is quite taxing on your immune system.

Your body must recognize the difference between its own tissues and the tissues of your baby.

Your immune systems primary goal is to eliminate and kill invaders, but even though we know that the fetus is “foreign” it’s not something we want your body to attack!

Because pregnancy puts increased demand on the immune system it may set the stage for the creation of antibodies to your thyroid (9).

These are the exact same antibodies that we see in autoimmune thyroiditis or Hashimoto’s thyroiditis, but is your body actually attacking your thyroid?

The exact situation is unclear but it looks like the presence of thyroid antibodies in your serum does not necessarily mean that you have Hashimoto’s (if it comes DURING pregnancy).

In most situations, these antibodies will fall after delivery, but that doesn’t mean you are out of the clear just yet.

The presence of antibodies in the serum during pregnancy does increase your risk of developing both maternal complications and thyroid disease later in your life.

But this begs the question:

Should assessing for thyroid antibodies be part of routine screening for pregnant women?

There is a good case to be made and it is something that I often do and recommend.

In my experience, I find having this information to be very helpful, especially in monitoring the pregnancy and in monitoring thyroid function after birth.

It’s helpful information to have, especially if the pregnant woman starts to develop postpartum depression or excessive hair loss after her pregnancy.

But your physician may feel differently.

With up to 11% of pregnant women having positive antibodies in their serum during pregnancy, it may be worthwhile assessing for this simple lab test.

The most important thing to realize is that while a huge percentage of women may have positivity to these antibodies it does NOT mean that their thyroid function is compromised.

In fact, the vast majority of women who fall into this category are considered to be “euthyroid” which is to say they have normal thyroid function.

On the other hand, it is also possible that some women may go into pregnancy with undiagnosed Hashimoto’s thyroiditis and may, therefore, fall into a different category.

So how do you differentiate these patients?

Often those women with Hashimoto’s will have hypothyroid-like symptoms BEFORE pregnancy and these symptoms may be worsened after they become pregnant.

If you are one of those women who have positive thyroid antibodies during pregnancy just realize that you have about a 20-40% chance of developing permanent hypothyroidism at some point later in your life (10).

Testing for Thyroid Disease During Pregnancy

If you suspect you have thyroid disease and you have the symptoms of thyroid disease then what is your next step?

Your next step should be to evaluate thyroid function in the serum with basic thyroid lab testing.

But this may be easier said than done.

The problem is that pregnancy results in the release of several hormones which all impact thyroid function (these include human chorionic gonadotrophin and chorionic thyrotrophin (11)) which may make the “standard” interpretation of TSH less valuable.

Because the TSH may be less helpful in pregnancy you will also need to assess for the free thyroid hormones (Free T3 and Free T4) (12).

So, if you are pregnant, what is considered the “complete” thyroid panel?

The following tests will give you the most information regarding your thyroid:

  • TSH (Thyroid stimulating hormone) – Your TSH will help you understand the pituitary function and its response to thyroid hormone in circulation.
  • Free T3 – Free T3 represents the active thyroid hormone and is the most biologically active thyroid hormone.
  • Free T4 – Free T4 is another biologically active thyroid hormone but less active than T3. It’s helpful to understand this value because it will help determine how much thyroid hormone is in “reserve”.
  • Thyroid antibodies (Both Thyroglobulin Antibody and Anti Peroxidase Antibody) – These thyroid antibodies may be a sign of Hashimoto’s or they may give you insight into your future risk of developing thyroid disease after pregnancy.

Thyroid testing, if thyroid disease is suspected, should be assessed as early as possible in your pregnancy (preferably with other routine tests). 

If an abnormality is suspected based on lab testing then supplementation with thyroid hormone should be the next step.

The reason for this aggressive treatment is because the fetus is dependent upon maternal (the mothers) thyroid hormone supply for the entire first semester and up to mid-gestation.

There may be some instances where you want to try all natural approaches to therapies, but this is not one of them.

The lack of thyroid hormone to the fetus may result in miscarriage or development issues.

Your Thyroid and Infertility

What if you are having a hard time getting pregnant or if you are suffering from miscarriages?

Thyroid disease may be the cause.

While thyroid issues aren’t always the cause of infertility, it is certainly a contributing factor, especially among many women (13).

Even though hypothyroidism occurs in only a few percentages of the population, thyroid disease is found in up to 20-30% of women suffering from infertility. 

The good news?

After treatment with thyroid hormone up to 75% of women who had trouble with conception were able to conceive (14).

The hard part isn’t necessarily treatment but identifying the disease in the first place. 

Your thyroid helps regulate progesterone levels and progesterone is required for sustaining pregnancy in early pregnancy (15).

Low thyroid function also causes menstrual irregularity which may lead to inconsistent cycles or anovulatory cycles (cycles where you don’t ovulate).

These issues can all be caused by minor changes to thyroid function which may not be picked up by standard lab tests.

Because of this, some maternal-fetal medicine practitioners maintain very strict guidelines regarding the “normal” range of those who are having issues with fertility.

If you are having issues with either getting pregnant or maintaining your pregnancy then you should closely evaluate a standard thyroid lab testing panel with optimal ranges in mind.

You can read more about how this idea here

Final Thoughts

The bottom line?

As a pregnant woman (or someone trying to conceive) make sure that you understand the basics of thyroid hormone and how it may influence your pregnancy.

Testing and understanding thyroid issues are especially important if you have a family history of thyroid disease or if you suspect you may have thyroid disease going into pregnancy.

The best way to avoid complications secondary to thyroid dysfunction is to go into pregnancy with your thyroid optimized.

Taking this approach will limit complications and ensure that you do not experience exaggerated symptoms during your pregnancy.

Now I want to hear from you:

Are you currently pregnant?

Do you have or suspect thyroid issues?

Is your physician willing to work with you?

Why or why not?

Leave your comments below!

#1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3179614/

#2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608008/

#3. https://www.ncbi.nlm.nih.gov/pubmed/17982337

#4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3625634/

#5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3266621/

#6. https://www.ncbi.nlm.nih.gov/pubmed/19178515

#7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3266621/

#8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4740614/

#9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3025805/

#10. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4518419/

#11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2425446/

#12. https://www.ncbi.nlm.nih.gov/pubmed/14510343

#13. https://www.ncbi.nlm.nih.gov/pubmed/16794427

#14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3657979/

#15. https://www.ncbi.nlm.nih.gov/pubmed/9846161

what to know about thyroid and pregnancy

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About Dr. Westin Childs

Hey! I'm Westin Childs D.O. (former Osteopathic Physician). I don't practice medicine anymore and instead specialize in helping people like YOU who have thyroid problems, hormone imbalances, and weight loss resistance. I love to write and share what I've learned over the years. I also happen to formulate the best supplements on the market (well, at least in my opinion!) and I'm proud to say that over 80,000+ people have used them over the last 7 years. You can read more about my own personal health journey and why I am so passionate about what I do.

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21 thoughts on “Everything you Need to Know About Your Thyroid and Pregnancy”

  1. I am currently 15 months postpartum and I suspect I am hypo. TSH is 1.321, FT4 is .82, FT3 is 3.0 and I am negative for antibodies. Before pregnancy I had no symptoms, after I have so many. Looking back I started getting symptoms mid-pregnancy. I am just starting to work with my physician. I have an appointment mid April and I will see if she is willing to work with me at that point. I want to start trying to conceive again later this year, but it seems like I need to get this under control before I even think about that.

    Reply
  2. I’m 9 months postpartum. I have developed a hyperthyroid and am trying to go about it the natural way so I don’t get dependent on medications. I’ve been suffering from hyperthyroid symptoms for a month now. I’m just wondering if I need Iodine for hyperthyroid, I don’t want to exacerbate it. (also I am still breastfeeding, and want to continue doing so) I am currently not taking Iodine, just Vitamin D3, B12, and Iron daily.

    Reply
  3. Hi,
    I’ve been taking both T4 and T3 for years. I told my endocrinologist that my husband and I were going to try to conceive. He said that if I get pregnant, I’ll need to stop the T3. So I decided to try to go off it right away, and he upped my T4. Within a couple of months, I noticed symptoms of weight gain, hair loss, skin breakouts. My TSH has dropped way low. I’m planning to get full thyroid panel soon, but I’m pretty sure that I need to go back on the T3. I’m fine with that as I’m not yet pregnant, but what happens when I do become pregnant? I don’t want to go off the T3 again, start having symptoms, and possibly have a negative impact on the baby. Why is T3 not good during pregnancy? Are there other options?
    Thanks!

    Reply
    • Hi Andrea,

      T3 can be used during pregnancy it’s just that most physicians don’t know how to dose it or don’t feel comfortable using it. I’ve used T3 in many pregnant patients without any issues.

      Reply
  4. Hi Dr. Childs,
    I am a nurse midwife with a patient taking Liothyronine and Levothyroxine in pregnancy. It is being managed by a functional medicine doctor at an outside practice. There is a difference in opinion between my back up physician and the FM doctor regarding where this patient’s TSH and FT4 levels in pregnancy should be and I came across your website in trying to find research explaining how LT3 affects FT4 levels. As you explain, LT3 can suppress both the FT4 and TSH. I was wondering if you have reference articles I can present to my colleagues explaining this? Your website is a great resource but I am hoping to have research articles or peer reviewed references to share with my group. Thanks in advance for your time and help with this.
    Best,
    Tera Martin, CNM

    Reply
  5. Hi, I am currently 8 weeks pregnant I was diagnosed with hypothyroidism last summer August 2019 and by this winter I changed my diet and lifestyle and my thyroid was back on track and my doctor took me off the levothyroxine.
    In December 2019 I became pregnant and my midwife put me back on it because my levels had elevated again however, I had a missed miscarriage around 6/7 weeks.
    Now, 8 weeks pregnant again my midwife checked my thyroid and I was a 3.94 tsh. She put me on the levo again I’m going in to see her again at 11 weeks for labs and check up and will ask her to include the additional tests you recommended. Do you have any other advice for me to continue a healthy pregnancy? I’ve been trying not to stress it this time but I still have that slight fear in the back of my mind of losing another baby, I would like to do anything I can to help silence that thought and feel more comfortable. What are the next steps after the additional lab tests that come through? I open to whatever will help me and my baby be healthy and safe. Thank you, I’ve learned a lot from you and would love to continue my journey to wellness with you.

    Reply
  6. hi.
    My TSH [3rd Generation] is 4.35 micro IU/mL. I was asked to take 25microg every morning on empty stomach.

    I did it for 2 months.
    Can you please tell what my condition is ? do i have to any Thyroid antibody test ?
    I am planning to get pregnant. But still no luck. I am about to be 31 years old in 3 months.
    Weight = 87Kg.
    Height 5′ 7″
    Can you please advise me how i can overcome my thyroid problem ?
    Is this a major problem which is stopping me from being pregnant ?

    Thanks in advance….!!

    Reply
    • Hi Jenny,

      It’s hard to know for sure without a lot more information but it’s certainly possible that your thyroid could limit your ability to get pregnant. As mentioned, though, you will need a more comprehensive workup aside from just your thyroid to make sure something else isn’t contributing such as weight, sex hormones, etc.

      There are many things you can do to try and improve your thyroid, though, and those can be found here: https://www.restartmed.com/natural-thyroid-remedies/

      Reply
  7. Hi Dr. Childs,

    I find your articles and videos tremendously helpful. Thank you for sharing your experience and knowledge with us.

    I may be wrong but from speaking with my physicians and researching online, it seems that TSH is considered the most valuable test for pregnant women whereas T4 and especially T3 are considered less or even not relevant. However, my personal multi-year experience living a normal TSH/T4 but low T3 gives me a strong intuition that T3 should be examined just as importantly as TSH in pregnant women.

    Could you please share your opinions about the role of T3 (vs. TSH and T4) in pregnancy and also in fetus development?

    Also, very specifically, what is your take on the following statement?

    “Early in pregnancy, T3 can’t enter your baby’s brain like T4 can. Instead, any T3 that your baby’s brain needs is made from T4. T3 is included in a lot of thyroid medicines made with animal thyroid, such as Armour Thyroid, but is not useful for your baby’s brain development. These medicines contain too much T3 and not enough T4, and should not be used during pregnancy. Experts recommend only using levothyroxine (T4) while you’re pregnant.” – Source: https://www.niddk.nih.gov/health-information/endocrine-diseases/pregnancy-thyroid-disease

    Thank you again very much!

    Reply
  8. Good evening. I has half my thyroid removed due to a large goiter in April. I currently do not take medication and my labs are great! I feel the best I have felt since my first child was born. We want to have another child but I have very worried that it will burn out my other half and make me dependent on medication. Have you had woman with half a thyroid go through pregnancy without medication? If they do have to take it do they come off of it after? Will pregnancy create a goiter on my other side?

    Reply
    • Hi Anna,

      I don’t recall anyone with that exact situation but it’s quite possible that it would be fine. It’s possible for the remaining half of the thyroid to hypertrophy and pick up the slack for the missing half. But it’s not always worth the risk given the importance of thyroid hormone in fetal development (especially brain development). In some sense, why take the risk to the developing child when thyroid medication would only be needed for 9 months? That’s obviously a choice you’ll need to make but that’s how I would think about it.

      Reply
  9. Hi there,

    This post is great, I just had a question. I developed postpartum hypothyroidism after my last baby 3 years ago and have since been levothyroxine 75mg. I am wanting to try for baby number two so I got my bloods done. My TSH came back as 0.82 mu/L, but my free T4 was 15.8 pmol/L and free T3 5.6 pmol/L. I am debating wether to lower my dosage to 50mg in the effort to lower my free T4 as im worried I may be taking to much? and have the potential to cause hyperthyroidism but as im wanting to conceive should i just stay on 75mg?

    Thank you
    Elisha

    Reply
  10. Hello Doctor
    What labs to look at if hashimoto symptoms are well controlled ONLY with cytomel during pregnancy Or mom T4 addition is a must for fetus?

    Thank you

    Reply
  11. I’m at a loss. I’ve had many hypo symptoms like hair loss, weight gain, cold intolerance, extreme exhaustion. My TSH is 1.65, T4 is 0.8, swollen thyroid with nodules, and high ALT. My doctors say there’s nothing wrong after years of struggling with this. I had a miscarriage two years ago and I’m now almost 5 weeks pregnant. I’m scared this will negatively affect the baby if I can’t get the doctors to do something.

    Reply
  12. Dr. Childs,
    Your blog and articles have become a valuable resource for me. Thank you for sharing your knowledge with the world!
    While I found your several articles on pregnancy and thyroid, I could not find any article on IVF and thyroid. My first frozen embryo transfer failed, and I want to ensure I am doing everything possible before the next attempt.
    I am not on any thyroid medications and I do not have any symptoms (I had hair loss issue, which 95% improved after I got on your Thyroid Adrenal Reset Complex!). My thyroid levels before embryo transfer were as follows – TSH: 1.76, T4, free: 1.15, T3, free: 2.8, Reversed T3: 19. My reproductive endocrinologist and endocrinologist wanted to see TSH below 2.5 to move ahead with the transfer, they did not care about T3, free or T4 free or reversed T3.
    I have never been diagnosed with hypo or antibodies. I see endocrinologist due to a history of acute thyroiditis that led to hyperthyroidism, then to hypo phase (without any symptoms) and then eventually back to normal range.
    Now, I am unsure if I should start thyroid medication before next embryo transfer, or after the transfer, or follow RE’s recommendation and check the TSH levels after confirmed pregnancy.
    Your guidance or any leads you can provide would be immensely appreciated.

    Reply

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