Specialist medical advice for pregnancy
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Q : Under-active Thyroid [ Sample Question ]

I have an under-active thyroid, will this affect my pregnancy? - 06/05/2010 by Sample Lady



Reply by Dr Lucy Mackillop
The important thing about pregnancy and hypothyroidism (an under-active thyroid) is that you must continue to take your thyroxine during pregnancy and you might have to slightly increase the dose. There is evidence that women who do not have enough thyroxine, have an increased risk of miscarriage, pre-term delivery, gestational diabetes and other pregnancy complications. Conversely, women with good control have better pregnancy outcomes.
Pregnancy is a time when your body has to work harder to support your growing baby. The thyroid gland is no exception. Your baby's thyroid gland does not start working until you are around 15 weeks pregnant, so it is particularly important that your thyroid function is perfect at the beginning of pregnancy when your developing baby relies on your thyroxine. The pregnancy hormones affect the carriage of thyroxine in the body making the reference range for thyroid function tests different in pregnancy. Therefore it is important to test the TSH AND the free T4 to check both are in the right range, and the range for TSH should be lower than the normal non-pregnant range.