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New trends in the management and guidance to reduce the risk of birth defects caused by antithyroid drugs

Apologies for the upset this paper could cause. The importance of its message is too great to ignore it.

Nuklearmedizin. 2015 Jun 23;54(3):106-11.

Graves'-Basedow disease in pregnancy. New trends in the management and guidance to reduce the risk of birth defects caused by antithyroid drugs.

Laurberg P, Andersen SL.

Author information

Peter Laurberg, professor, M.D., Department of Endocrinology, Aalborg University Hospital, 9000 Aalborg, Denmark,


Thyroid hormones are essential development factors and maternal thyroid dysfunction may cause pregnancy complications and diseases in the fetus/child. In the present review we discuss new data on the incidence of Graves'-Basedow disease (GBD) in and around pregnancy, and how hyperthyroidism may affect the risk of spontaneous abortion and stillbirth. A special concern in pregnant women is the potential side effects from the use of antithyroid drugs (ATDs). One type of side effects is the allergic/toxic reactions to the drugs, which seem to be similar in and outside pregnancy, and another is that ATDs tend to over treat the fetus when the mother with GBD is made euthyroid. To avoid fetal hypothyroidism, the lowest possible ATD dose should be used to keep maternal thyroid function at the upper limit of normality with low serum TSH. Birth defects after the use of methimazole (MMI) (or its prodrug carbimazole) have been considered to be very rare, and no risk has previously been associated with the use of propylthiouracil (PTU). However, a recent Danish national study found that 1/30 of children exposed to MMI in early pregnancy had birth defects associated with this, and many defects were severe. PTU exposure was associated with defects in 1/40, and these defects were less severe. Proposals are given on how to reduce the risk of ATD associated birth defects.


Antithyroid drugs; Basedow’s disease; Graves’ disease; birth defects; epidemiology; incidence; pregnancy; spontaneous abortion; stillbirth; thyrotoxicosis; thyroid disease

PMID: 26105719 [PubMed - in process]

7 Replies

"ATD's tend to over treat the fetus when the mother with GBD Is made euthyroid......"

Difficult decision to treat the baby or the mother?



I felt that having a mechanism suggested helps a bit. You can see that using the minimum possible anti-thyroid drug appears rational. Next step, probably work out how to achieve that. We see a lot of people who have difficulty getting their anti-thyroid drug dose right for them. With the additional difficulties of pregnancy, they need all the help they can get.


Yes, perhaps the addition of weekly blood tests would give a clearer picture except thyroid meds take up to 6 weeks to be fully effective and a small proportion of mothers do not realise they are even pregnant until several months.

Also learning to take temp and pulse every morning with accommodation for an increase due to baby.

I can't see it happening though with the exception of those mothers who have planned the pregnancy so are expecting the changes and are familiar and educated in thyroid issues.



Though anti-thyroid drugs do have a much quicker effect (once they have been on them for a few weeks).


Yes of course. I forgot as am not familiar as am hypo myself.


Don't we all! I certainly have to pinch myself at times. :-)




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