Thyroid UK

29 weeks Pregnant and On 25mg Carbimazole

Hello everyone..I was just wondering if anyone can share with me if they have same experience like me..I was diagnoised hyperthyroid last year sept and I was put on 20 mg carbimazole and Bisoprolol..within two months on treatment I fell pregnant and my endocri told me to stop taking bisoprolol..I continued with carbimazole until yesterday when I went to see her and increased my dose to 25 mg reason being I'm having terrible palpitations everytime after food.Am so worried about the side effects on the baby more so that she increased ny dose ..the other thing is she cannot do alot about Carbimazole as it is the only product available in my country.Please advice....

3 Replies

Welcome to the forum, Ellenm-2.

Carbimazole can cross the placenta barrier in the first Trimester so in the UK pregnant women are often switched to Propylthiouracil (PTU) for the first trimester and later if they breast feed as Carbimazole will also be in breast milk.

In the UK all babies are given a heel prick blood test to check for hyper and hypothyroidism. If it isn't done as a matter of course in your country you should request it. If you are unable to switch to PTU while you are breast feeding you should also ask that your baby's thyroid levels are checked regularly.


Thank you so much..I am definitely going to request regular checks on the baby..Im just hoping the Carbimazole doesnt do any harm to my poor little bb..


Ellen, If the baby was in any distress I think it will have been picked up at your ante natal checks. I hope all goes well and you have an easy labour :)


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