Thyroid underactive living in pregnancy
Informed by recognized medical guidance
Overview
An underactive thyroid (hypothyroidism) means your thyroid gland doesn’t make enough thyroid hormone. This hormone helps control your body’s energy and growth. During pregnancy, it’s especially important for your baby’s brain and development. With proper care, most women with an underactive thyroid have healthy pregnancies.
Key facts
- Thyroid hormone is vital for your baby’s brain and nervous system development.
- Untreated underactive thyroid during pregnancy can increase risks for both mother and baby.
- Treatment is safe and effective — usually with a medicine that replaces the missing hormone.
- You will need regular blood tests to make sure your thyroid levels stay in a healthy range.
- Most women with well-controlled hypothyroidism have normal, healthy pregnancies.
Yes, underactive thyroid is common in women of childbearing age. Many women are diagnosed before pregnancy, but sometimes it starts during pregnancy.
It affects pregnant women, especially those who already have hypothyroidism or have a family history of thyroid problems. Women with certain autoimmune conditions (like type 1 diabetes) are more likely to develop it.
Symptoms
- Severe shortness of breath or chest pain
- Fainting or passing out
- Very fast or irregular heartbeat
- Sudden confusion or severe weakness
- ⚠Symptoms of a thyroid storm (very high fever, sweating, rapid heart rate, agitation) – seek immediate medical help
Common symptoms
- Feeling very tired or sluggish
- Weight gain that is more than expected
- Constipation
- Feeling cold all the time
- Dry skin and hair loss
- Muscle aches and weakness
- Problems with memory or concentration
- Depression or low mood
Causes
Main causes
- Hashimoto’s disease – an autoimmune condition where your immune system attacks your thyroid gland.
- Treatment for an overactive thyroid (like radioactive iodine or surgery) can sometimes lead to an underactive thyroid.
- Certain medicines or treatments (like lithium or amiodarone) can affect thyroid function.
- Iodine deficiency – though rare in countries with iodized salt.
Risk factors
- Having a family history of thyroid disease
- History of autoimmune disease (like type 1 diabetes or celiac disease)
- Previous thyroid surgery or radiation to the neck
- Being older than 30
- Having a previous miscarriage or preterm birth
- Being of Caucasian or Asian descent
When to see a doctor
See a doctor urgently if:
- If you are pregnant or planning pregnancy and have symptoms of underactive thyroid – see your doctor as soon as possible.
- If you have a known thyroid condition and experience any new or worsening symptoms.
Book a routine appointment if:
- All pregnant women should have their thyroid function checked if they have risk factors or symptoms.
- If you are already on thyroid medicine, you will need regular blood tests every 4–6 weeks during pregnancy.
Diagnosis
A simple blood test measures your thyroid hormone levels (TSH and free T4). During pregnancy, your doctor uses special reference ranges to interpret the results.
Tests that may be done
- Blood test for TSH (thyroid-stimulating hormone)
- Blood test for free T4 (thyroxine)
- Sometimes an antibody test to check for Hashimoto’s disease
What to expect at your appointment
Your doctor will explain your results and start treatment if needed. You will have regular follow-up blood tests to keep your levels in the target range for pregnancy.
Treatment
Treatment involves taking a daily medicine that replaces the missing thyroid hormone. This is safe for you and your baby. You will need to take the medicine exactly as prescribed, usually on an empty stomach, and wait before eating or taking other medicines.
Self-care at home
- Take your thyroid medicine at the same time every day, ideally first thing in the morning with water.
- Wait at least 30 minutes to 1 hour before eating or drinking anything other than water.
- Do not take your thyroid medicine at the same time as prenatal vitamins, calcium, or iron supplements – wait at least 4 hours.
- Keep all your follow-up appointments for blood tests.
- Eat a balanced diet with enough iodine (but do not take iodine supplements unless your doctor advises).
Medical treatments
The main treatment is a thyroid hormone replacement medicine, which you take as a daily pill. Your dose will likely need to increase during pregnancy. Your doctor will adjust the dose based on your blood tests. Do not change your dose without talking to your doctor.
When is surgery considered?
Surgery is not part of treatment for underactive thyroid. In rare cases, if there is a large goiter or cancer, surgery might be considered, but not during pregnancy unless absolutely necessary.
Living with this condition
Taking your thyroid medicine daily and having regular blood tests becomes part of your routine. Many women feel normal once their levels are stable. Communicate with your healthcare team about any symptoms.
Lifestyle tips
- Get enough rest – pregnancy can be tiring, especially with hypothyroidism.
- Manage stress through relaxation techniques like deep breathing or gentle exercise.
- Stay active with walking or prenatal yoga, as approved by your doctor.
- Avoid smoking and limit alcohol (best to avoid alcohol completely during pregnancy).
Diet and exercise
Eat a healthy pregnancy diet rich in fruits, vegetables, whole grains, lean protein, and dairy for iodine. Do not use soy or high-fibre supplements in large amounts near your medicine time. Gentle exercise is good, but check with your doctor first.
Mental health and emotional wellbeing
Hypothyroidism can cause low mood or depression. Pregnancy hormones can also affect your mood. Talk to your doctor if you feel sad, anxious, or overwhelmed. Treatment can help, and support is available.
Prevention
In many cases, you cannot prevent hypothyroidism because it is often caused by an autoimmune condition. However, if you have risk factors, getting your thyroid checked before pregnancy or early in pregnancy can help you manage it well.
Screening programmes
Routine screening for thyroid problems is not recommended for all pregnant women, but your doctor may test you if you have symptoms or risk factors.
Complications
If left untreated
- Higher risk of miscarriage
- Preterm birth (baby born too early)
- Preeclampsia (dangerous high blood pressure in pregnancy)
- Low birth weight baby
- Problems with the baby’s brain development
Long-term outlook
With proper treatment, the outlook is excellent. Most women with well-controlled hypothyroidism have healthy pregnancies and healthy babies. Your doctor will monitor you closely to keep your thyroid levels in the right range.
Find support
International organisations
Local organisations
- NHS Choices ↗ · UK
Helplines
External links open third-party websites. Ruqelo Health is not responsible for external content. Listing an organisation does not imply endorsement.
Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
Related conditions
Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 29, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.