TSH Levels During Pregnancy

The reference range for TSH during pregnancy is as follows:

First Trimester: 0.1 – 2.5
Second Trimester: 0.2-3.0
Third Trimester: 0.3 – 3.0

Values out of range need to be investigated and managed accordingly. They may indicate Hypo (underactive) or Hyper (over active) state of the maternal thyroid gland.

Why Are TSH Values Lower During Pregnancy?

Normally, TSH levels are slightly lower in pregnant women than in non pregnancy females. This is because a part of the work that TSH does is taken over by the pregnancy hormones, chiefly HCG.

HCG is highest during the first trimester, lowering TSH to the maximum extent during this phase. Gradually, as pregnancy progress, TSH levels may be seen to rise quietly, though modestly.

Role of TSH

TSH stimulates the thyroid gland, which is a butterfly shaped gland, just below our adam’s apple in the neck. It has two lobes, located one on each side.

On being stimulated, the gland secretes two important hormones, T3 and T4, which control the body metabolism.

Why is TSH So Important in Pregnancy?

The two thyroid hormones are very important for the baby growing in the womb. This is because the baby doesn’t have its functioning thyroid while in womb, and it completely depends upon the maternal supply for this hormone.

T3 and T4 are required for the neurocognitive development of the growing baby. This means the baby’s mental faculty needs this hormone to develop. It afects the baby’s intelligence, thinking power and over all brain tissue development.

Lack of Thyroid Hormones in Pregnancy- Complications

  • Preterm delivery of the fetus
  • Low birth weight baby
  • Miscarriage
  • Low IQ
  • Cognitive disorders in the baby.

High TSH During Pregnancy

If your TSH is as high as 2.5 to 3, guidelines recommend measuring of T4 levels.

If T4 is also low, the condition may be called Hypothyroid. TSH levels needs a correction by medications to avoid fetal complications.

If T4 levels are alright, the baby is getting enough of this hormone for development. We may call the situation as subclinical Hypothyroidism.

Here, anti thyroid antibodies need to be investigated. If present, treatment is recommended. Lack of treatment may affect the fetal IQ levels.

Very high TSH levels, say 5 or above, need immediate treatment, regardless of the T4 values.

Hypothyroid, Planning Conception

The need for thyroid hormone by your fetus is maximum in early first trimester. So, if you plan conception, it’s advisable to correct your thyroid status first.

The recommended goal is to bring the TSH levels to 2.5 or low.


Accurate correction of TSH levels is a must. If levels are high, anti-thyroid medication with close monitoring of pregnancy may be given.

It would also be necessary to regularly get TSH levels checked up. This is essential for continuous dose alterations of the medicine, if required.

Medical Advice (Q&As) on “Levels of Thyroid Stimulating Hormone (TSH) in Pregnancy

  1. Helen

    Hi, I am 32 years old. I got my thyroid checked. The result is my T3 T4 are normal but TSH is below normal 0.375. I don’t what does this mean.

    1. Buddy M.D. Post author

      Your TSH value is slightly low. The average TSH range in healthy individuals is 0.40-4.00 mIU/L

      You may put this value in our lab test checker to know your exact status and common conditions that may lead to such values.

  2. Nadiya

    Hi sir/madam

    I conceive my pregnancy between 5-to 9 march 2014. At that time I was taking medicine thyronorm 75 mcg.
    My TSH was 6.30 range 0.27–4.20ui/ml

    I said this to gyne. He said continue to take medicine.

    After the 6 week pregnancy he advice to test the thyroid (20 April 2014)

    TSH become 2.670 range 0.39 –5.55 uu/ml

    He advice to take continue the same dose.
    Again test the thyroid at 16 weeks pregnancy (12 July 2014)

    TSH become 1.675 range 0.39– 5.55ui/ml

    I am worried for my baby because some where I read that at 6 to 12 weeks pregnancy, baby requires thyroid hormone, so it should increase the dose at that time immediately. It hammer on baby IQ.

    On the basis of my lab result above please. Reply is it true in my case?

  3. Pooja

    My TSH 6.30 t 3 t4 normal. I was normal before taking thyronorm but now feeling ill with thyroxine. Feeling fever, headache, acne, dark skin, late menstrual period etc. What do I do? My age is 30.

    1. Buddy M.D. Post author

      There are many other conditions that may cause your TSH levels to be high, apart from thyroid problems.

      Put your TSH value in our lab test checker to see the medical conditions that may cause this reading.

      You need to be evaluated thoroughly to make a diagnosis. If thyronorm is not suiting you, consider seeing a doctor again for re evaluation of your condition.

  4. Pooja

    Which multivitamin is good with doxycycline for alternate use morning and night. If I don’t have symptom of hypothyroidism but autoimmune disease then, which medicine is good for me. Thyronorm is not suiting me but body feeling like swelling. When I ate curd, body swelling increased.

  5. Pooja

    Now on 25 mcg thyronorm by 2 months causing constipation and severe headache, sleepless I think I must stop taking med?? 25 mcg is also high may be and 2 month med can boost my mild hypothyroidism. I stopped med from last 4 days, stopped headache and constipation. Is these possible med boost my thyroid?

    1. Buddy M.D. Post author

      The medicine is external thyroid hormone, being given to you as your body is unable to produce its own hormone.

  6. Pooja

    Hello sir, after taking doxycycline with thyroxine, all side effects are stopped suddenly. Now I can take easily thyronorm. My doctor didn’t checked my anti-TPO.

    1. Buddy M.D. Post author

      You may get them checked if you want.

      Though the presence of these antibodies suggest some autoimmune thyroid disease, these are not diagnostic, just suggestive of the disease.

  7. SS

    My TSH is 3.23 and i am 7 weeks pregnant. Is 3.23 TSH level is high and will it affect baby developement?

    1. Buddy M.D. Post author

      Levels of TSH appear to be high. Do you have any clinical symptoms indicating hypothyroidism? Clinical correlation with the lab levels of the hormone is important to assess the exact status.

      You shouldn’t be hypothyroid. This would affect the neural development of the baby.

  8. Asha

    I use to take thyrox 12.5 before pregnany in the 3 rd month of my pregnancy i checked …. nd tsh is 2.2 but at the end od 7 month again i checked so level of tsh is 4.1 so it will affect the mental health of my baby

    1. Buddy M.D. Post author

      It’s better to keep your TSH under more tight controls. Talk to your doctor about increasing your medicines, if required.

  9. Lina

    I just found out I’m pregnant. 4w2 days. Last week I had my tsh checked. It was 11.4. My obgyn gave me medication of 50mcg. Will that we enough until I can get an appointment with an endocrinologist? I’m worried about my baby.

    1. Buddy M.D. Post author

      Get a repeat TSH to see the results. You need to bring your TSH within the normal range asap.

  10. Toniann

    Is a TSH of .75 ok in the first trimester of pregnancy? I’m on 50 mcg synthroid and have blood work every 4 weeks. I’m asking because everything I’ve read says TSH should be between 1-2.

  11. sonia

    hi..my tsh level is 46…how much dose of thyronorm medicine i should take..i am taking 25mcg thyronorm now…tanx

    1. Buddy M.D. Post author

      Assessment about the dose is made clinically by a doctor after examining you. He takes into consideration, both, your symptoms and TSH levels.

  12. Mimi Datta

    im 11week pregnant. my tsh level is 6.15.. im worried about my baby??my obgyn suggest me to take thyrone 37.5mg ..plzz suggest me wat i do???

    1. Buddy M.D. Post author

      You appear to be clearly hypothyroid. Thyrone needs to be started at the earliest, with careful monitoring of your hormonal levels repeatedly. This would help your doctor to adjust the dose.

  13. Me

    I’m just pregnant now.. 3weeks.
    Had my TSH tested..It came 5.3( range .4-4.2)
    I’m already taking thyronorm 25mcg. Should I increase dosage. I’m worried . Will it not cause any harm to my pregnancy?

    1. Buddy M.D. Post author

      You need to get your thyroid levels checked again, after taking the medication. If the levels are alright, the dose is adequate. Else, your doctor may consider increasing it.

      It’s very essential to keep the levels of TSH strictly within the normal range.

  14. Depeka Akter

    I am 10th week pregnant but my hTSH level is 12.60 and now I take medicine for this. Please tell me it is harmful for my baby?? ?

    1. Buddy M.D. Post author

      You appear to be grossly hypothyroid. Immediate correction is needed. You need to take thyroid pills, under your doctor’s supervision.

      Yes, this is very damaging for your baby. Especially his mental development would be adversely affected. So, urgent correction is required.

  15. Karlee

    I’m in my 3rd Trimester. My t4 and t3 levels are normal but my TSH is 3.23. What does that mean? Before being pregnant I was Hyperthyroid and on PTU. Once becoming pregnant my thyroid levels because normal and I’ve been off meds my entire pregnancy.

    1. Buddy M.D. Post author

      You may be slightly towards the Hypo side now. Most cases as yours do not require medications, unless there are any symptoms. You need to be evaluated by your doctor.

  16. angela e

    I am 9 weeks and my TSH is 3.47 my doctor suggested i start on medications… will they affect baby? will this level of tsh harm my baby please advise?
    im terrified

    1. Buddy M.D. Post author

      Yes, you should be on medicines for thyroid to control your TSH levels at the earliest. Though all medications do have some side effects, however, medicines would do less harm to the baby than elevated TSH levels.


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