Short answer: NIDDK says hypothyroidism in pregnancy is usually caused by Hashimoto's disease. Your thyroid levels get checked through blood tests. The American Thyroid Association (ATA) says women with established hypothyroidism should have a TSH test as soon as pregnancy is confirmed, and it recommends the same early TSH check for women at high risk for thyroid disease. NIDDK says that when doctors diagnose hypothyroidism in pregnancy, they may also look for certain antibodies. For women already being treated, the ATA, NIDDK and the Office on Women's Health (OWH) each give a different interval for repeat tests, so ask your doctor which schedule is yours. Treatment, and any change to it, is your doctor's call. If you had hypothyroidism before you became pregnant and are being treated, NIDDK says to contact your doctor as soon as you know you're pregnant. The American College of Obstetricians and Gynecologists (ACOG) says that with treatment, most pregnant women with thyroid disease can have healthy babies.
If you have Hashimoto's and you've just found out you're pregnant, this is for you. You're allowed to have thyroid questions on top of everything else, and you're allowed to ask them early.
Why your thyroid gets more attention in pregnancy
NIDDK says thyroid hormones are crucial for normal development of your baby's brain and nervous system. It says that during the first trimester, the first 3 months of pregnancy, your baby depends on your supply of thyroid hormone, which comes through the placenta. The ATA puts it this way: "For the first 18-20 weeks of pregnancy, the baby is completely dependent on the mother for the production of thyroid hormone." By mid-pregnancy, the ATA says, the baby's thyroid begins to produce thyroid hormone on its own.
NIDDK says hypothyroidism in pregnancy occurs in 2 to 3 out of every 100 pregnancies, and that it's usually caused by Hashimoto's disease.
It can also be easy to miss. NIDDK says thyroid problems can be hard to diagnose in pregnancy, because of higher levels of thyroid hormones and symptoms that occur in both pregnancy and thyroid disorders. OWH's Hashimoto's page says symptoms of normal pregnancy, like fatigue and weight gain, can make it easy to overlook thyroid problems in pregnancy. And the ATA says "Women with mild hypothyroidism may have no symptoms or attribute symptoms they have to the pregnancy."
So two things run side by side from here: the blood tests your doctor orders, and how you feel in between them. Your doctor reads the first. You're the one who can keep the second.
Osmi's lab album is one place to keep the results. Photograph the paper, upload the PDF, or type one number. Osmi files every result with its unit, date, lab and printed range, and a re-draw stacks on the same card and shows what moved. Osmi doesn't tell you what a result means about you. For the days in between, the daily check-in takes about a minute: answer seven questions or speak with Rose, your thyroid mascot, and every answer lands on the same record as your labs, cycle, and sleep. If you're pregnant, nothing else in Osmi depends on a cycle day: your check-ins, your labs, your sleep, and your appointment sheet all work exactly the same.
What gets checked, and who says so
| What gets checked | When | Who says so |
|---|---|---|
| A TSH test | As soon as pregnancy is confirmed, for women with established hypothyroidism | ATA |
| A TSH test | As soon as pregnancy is confirmed, for women at high risk for thyroid disease, such as those with prior treatment for hyper- or hypothyroidism, a family history of thyroid disease, a personal history of autoimmune disease, or a goiter | ATA |
| Blood tests of your thyroid hormone levels, and possibly antibodies | When your doctor is checking for hypothyroidism in pregnancy | NIDDK |
| Thyroid function tests, repeated, if you're already being treated | Approximately every 4 weeks during the first half of pregnancy | ATA |
| Thyroid hormone tests, repeated, if you had hypothyroidism before pregnancy and are being treated | Most likely every 4 to 6 weeks for the first half of pregnancy, and at least once after 30 weeks | NIDDK |
| Thyroid hormone tests, repeated, if you're being treated for hypothyroidism from Hashimoto's | Likely every six to eight weeks during your pregnancy | OWH |
| The ranges your results are read against | Throughout pregnancy | ATA, which says the thyroid is functioning normally if TSH and Free T4 remain in the trimester-specific normal ranges throughout pregnancy |
Three US bodies, three intervals for repeat tests. You don't need to settle that yourself. Ask your doctor which schedule they want for you, and write it down in their words.
On the ranges: the ATA says thyroid function tests change during normal pregnancy, under the influence of two hormones, hCG and estrogen, and it names trimester-specific normal ranges. Your doctor reads your result against them. Osmi files every result with the range your lab printed, and Osmi doesn't have a range of its own. Which range applies to a pregnancy result is a question for your doctor.
Who's on your team
OWH says that during pregnancy you may need to see both your OB/GYN and an endocrinologist, which it describes as a doctor who treats people with hormone problems. If you see both, ask who orders your thyroid tests and who you call with a thyroid question. Two doctors help most when you know which one to call.
Treatment is your doctor's call
NIDDK's and the ATA's pregnancy pages and OWH's Hashimoto's page each have a section on treating hypothyroidism in pregnancy. Treatment, and any change to it, is your doctor's call. Osmi never diagnoses, treats, or prescribes, and it will never ask you to change medication.
What you can do is make the call early. NIDDK's advice for women who had hypothyroidism before they became pregnant and are being treated: "Contact your doctor as soon as you know you’re pregnant." OWH says that if you have symptoms of an underactive thyroid or notice a goiter, it's important to tell your doctor or nurse.
Will my baby be OK?
ACOG answers the question of whether you can be treated for thyroid disease while pregnant this way: "Yes, it is important to be treated if you have thyroid disease when you are pregnant. Untreated thyroid disease can pose serious risks to a woman and her fetus during pregnancy. With treatment, most pregnant women with thyroid disease can have healthy babies."
NIDDK says untreated hypothyroidism during pregnancy can lead to preeclampsia, anemia, miscarriage, low birthweight, stillbirth and, rarely, congestive heart failure, and that "These problems occur most often with severe hypothyroidism." The ATA says complications are more likely to occur in women with severe hypothyroidism, and that "Some risks also appear to be higher in women with antibodies against thyroid peroxidase (TPO)." If you don't know whether your antibodies have been tested, see thyroid antibodies, explained, and ask.
NIDDK's list is about untreated hypothyroidism. If anything on it worries you, take it to your doctor as a question.
What to write down
- The date your pregnancy was confirmed, and the date you told your doctor.
- Every blood draw: the date, the test names, the result, the unit, the lab, and the range printed on the report.
- Which doctor ordered each test.
- The schedule your doctor gave you for repeat tests, in their words.
- How you've felt, dated, in your own words. NIDDK says symptoms of an underactive thyroid are often the same for pregnant women as for other people with hypothyroidism, and its list includes extreme tiredness, trouble dealing with cold, muscle cramps, severe constipation, and problems with memory or concentration.
- Anything new in your neck, with the date you noticed it.
- Every question you think of between visits.
A record like this shows what sat next to what. It doesn't show what caused what. Osmi works the same way: where two things line up, it says they track with each other and it stops there.
Questions to take to your first appointment
- Should my TSH be checked now that my pregnancy is confirmed?
- Were my thyroid antibodies tested, and should they be now?
- How often will you check my thyroid levels during this pregnancy?
- Which range are you reading my results against?
- Is anything about my treatment changing, and who do I call about it?
- Should I see an endocrinologist as well as my OB/GYN?
- What would you want me to call you about between visits?
- What follow-up do you want for my thyroid after the birth?
ACOG's own advice is short: "If you have further questions, contact your ob-gyn." Osmi's appointment sheet is one page, built from the record you already keep, that you share with your practitioner in one tap. It doesn't diagnose anything and it doesn't read your results for you.
After the birth
NIDDK says postpartum thyroiditis is an autoimmune condition similar to Hashimoto's disease, and OWH says some women develop thyroid problems in the first year after giving birth. For what to write down in that year, see postpartum thyroiditis: what to write down.
Make the first call early, write down every draw, and bring your questions on paper.
Questions women ask about Hashimoto's and pregnancy
Can Hashimoto's affect pregnancy? OWH's Hashimoto's page says the unborn baby's brain and nervous system need thyroid hormone to develop, and that untreated or poorly treated Hashimoto's disease can lead to miscarriage, birth defects, or other problems. ACOG says that with treatment, most pregnant women with thyroid disease can have healthy babies. OWH says that if you have symptoms of an underactive thyroid or notice a goiter, it's important to tell your doctor or nurse.
What thyroid tests are done during pregnancy? The ATA says women with established hypothyroidism should have a TSH test as soon as pregnancy is confirmed. It recommends the same early TSH check for women at high risk for thyroid disease, such as those with prior treatment for hyper- or hypothyroidism, a family history of thyroid disease, a personal history of autoimmune disease, or a goiter. NIDDK says that to diagnose hypothyroidism in pregnancy, your doctor will review your symptoms, do some blood tests to measure your thyroid hormone levels, and may also look for certain antibodies.
How often is your thyroid checked during pregnancy? For women already being treated, the ATA, NIDDK and OWH give different intervals. The ATA says thyroid function tests should be checked approximately every 4 weeks during the first half of pregnancy. NIDDK says your doctor will most likely test every 4 to 6 weeks for the first half, and at least once after 30 weeks. OWH says likely every six to eight weeks. Ask your doctor which schedule they want for you.
Why is hypothyroidism hard to spot during pregnancy? NIDDK says thyroid problems can be hard to diagnose in pregnancy because of higher levels of thyroid hormones and symptoms that occur in both pregnancy and thyroid disorders. OWH says symptoms of normal pregnancy, like fatigue and weight gain, can make it easy to overlook thyroid problems. The ATA says women with mild hypothyroidism may have no symptoms or attribute symptoms they have to the pregnancy.
Do I need an endocrinologist if I'm pregnant with Hashimoto's? OWH says that during pregnancy you may need to see both your OB/GYN and an endocrinologist, a doctor who treats people with hormone problems. Ask your OB/GYN whether they want you to see one, and who orders your thyroid tests if you see both.
Will my baby be OK if I have hypothyroidism? ACOG says it is important to be treated if you have thyroid disease when you are pregnant, and that with treatment, most pregnant women with thyroid disease can have healthy babies. NIDDK says untreated hypothyroidism during pregnancy can lead to problems such as preeclampsia, anemia and miscarriage, and that these problems occur most often with severe hypothyroidism. Talk to your doctor about your own results.
Educational, not medical advice.
