Thyroid UK
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Subclinical Hypothyroidism in preganancy

I'm currently 21 weeks pregnant. At 18 weeks I went to the doctor due to extreme tiredness, like nothing I'd ever felt before. After some persuasion, my GP agreed to run a blood test, and last week I received a call to say my thyroid levels were 'a bit off'. It seems that I'm subclinical hypothyroid with anti-thyroid antibodies present. I've been prescribed levothyroxine (25mg) and am due to see a consultant in around 4-5 weeks time.

From the brief explanation I was given by my GP, and from what I've read online, it seems that hypothyroidism can lead to severe complications in pregnancy (preterm birth, still birth, pre-eclampsia, placental abruption etc.) and also to fetal developmental defects and intellectual impairment in the child.

So obviously I'm now pretty worried! Does anyone have any knowledge or experience of hypothyroidism in pregnancy and might be able to put my mind at rest?

For reference, my levels are:

TSH: 5.23 mU/L (above reference limit of 0.54-4.25)

FT3: 3.7 mU/L (within reference limit of 3.5-6.2)

FT4: 10.0 mU/L (within reference limit of 8.0-16.0)

TPO antibody: 671 (above reference limit of 0-8.0)

7 Replies

It is recommended that TSH is kep below 2.5 for the first trimester and below 3.0 for the remainder of the pregnancy. Given your condition has recently come on and it takes a few weeks for the levothyroxine to build up in your system I'd ask your doctor to prescribe 50 mcg, which is not a large dose. This is especially so if you are still very tired, in this case if you can't get an appointment soon I'd telephone the doctor and say you would like to take two tablets until you can see them.

There are increased risks if the TSH is elevated but these are small risks, you should not be unduly alarmed. For the first half of the pregnancy the baby relies on the mother's thyroid for hormone until it grows it's own thyroid in the second half.

Your blood tests indicate you have autoimmune hypothyroidism, which is likely to progress, meaning you will need higher doses in the coming months. This is the normal progression for hypothyroidism. Now is a good time to be a bit assertive and insist you receive adequate treatment, doctors can be a bit too relaxed if they don't have specialist knowledge in this area. One point to watch out for is that hypothyroidism can occasionally lead to depression and in your case this could be mistaken for post baby blues. If you start to feel down make sure they keep on top of your thyroid problem.

As I said there is an increased risk but it's a small risk so don't let it worry you. Perhaps a female member can let you know about what it is like to be hypo and pregnant.



Mousie, the foetus is dependant on maternal thyroid hormone until 12/13 weeks when it develops it's own thyroid. It's probably the foetal demand which has depleted your own thyroid hormone. The 13 week development check would have shown whether there were any developmental defects and taking thyroid replacement now should build protection against pre-term, still birth, pre-eclampsia etc.

It is usual to increase Levothyroxine by 25-50mcg in hypothyroid women when pregnancy is confirmed so I think the 25mcg dose is inadequate and should be increased to 50mcg as Jimh111 suggested above.

We have had several 'forum' babies born to hypothyroid mums but apart from posting the announcement of a healthy son or daughter they're generally too busy to update.


I started taking Levothyroxine just before i fell pregnant with my first child. Suffered a miscarriage previously, but was not diagnosed at that point. I had asked to be tested as all female side of my family have thyroid problems, but my doctor told me i wasn't fat enough to have an under-active thyroid. Anyway cut a long story short, i have two beautiful girls 9 and 12. The first born was premature but that was issues with blood pressure. Both had their thyroid levels checked when they were born. And both were fine. Chances are later on in life they might develop thyroid issues, as my Gran, Aunties, Mum and 2 sisters are all on thyroid medication. Try not to worry and enjoy your pregnancy. Its a magical time.



I am currently 32 weeks and hypothyroid. This developed in a previous pregnancy 5 years ago very similar to yourself, picked up in the 2nd trimester. I had all of the same worries about worst case scenarios, however I started on 25mcg initially and increased to 50mcg. All was well with my pregnancy, birth and baby. After delivery, make sure your thyroid is checked 4 weekly to ensure there are no erratic changes as you have antibodies and hashimotos is more unpredictable. Feel free to message me if you need any other advice or info. Take care.


Thank for the replies, I definitely feel reassured. Had a letter today with the appointment to see the endo, booked in for 3 weeks time. I have a blood test a week before so I'm guessing the consultant will adjust my dose then if necessary. Just one more thing, does having antithyroid antibodies make congenital hypothyroidism more likely? I haven't been able to find anything conclusive on this.


I was told by my endo that it is not likely. However, your baby will be given additional thyroid blood tests after birth.


When you do get your blood results make sure your doctor looks at t3/t4 and not just tsh. Tsh can be lowered but your t3/t4 need to move into the upper part of the range for you to really be feeling better.


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