Thyroid disease can cause various problems for a woman who wants to get pregnant:
- thyroid problems can cause women not to ovulate so it may be difficult to conceive if you have undiagnosed or undertreated hypothyroidism 1
- hypothyroidism and subclinical hypothyroidism can cause an increase in prolactin, the hormone that induces and maintains the production of breast milk. It is not clear whether high prolactin (hyperprolactinaemia) has a negative effect on fertility but if you have high prolactin levels, do get your thyroid function checked2
- there is increasing evidence that autoantibodies cause subfertility and early pregnancy loss, even in euthyroid women1,3
- undiagnosed hyperthyroidism can cause miscarriages, premature births and problems for the baby 1
NICE state that all women who have overt hypothyroidism or subclinical hypothyroidism and who are planning a pregnancy or who are pregnant should have a referral to an endocrinology specialist. 4 Your doctor should discuss the initiation of treatment and dosage with an endocrinologist whilst waiting for the referral.
NICE also state that thyroid function tests should be checked before conception if possible and that if they are not within the euthyroid range, they should be advised to delay conception and use contraception until the woman is stabilised on levothyroxine.4
There have been several studies of pregnant women with high TPO antibodies which found that their children had impaired intellectual performance whether or not the mothers also had experienced clinical thyroid dysfunction so you need to ensure that your doctor tests for these before trying for a baby. 5
Your doctor should also explain that you are likely to need more levothyroxine during pregnancy and that your dosage should be adjusted as early as possible in the pregnancy to reduce the chance of problems for you and your baby.
2014 – Guidelines for the Treatment of Hypothyroidism
2015 – Management of primary hypothyroidism : statement by the British Thyroid Association Executive Committee
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Date updated: 04/05/21 (V1.1)
Review date: 12/03/22
- 1.Jefferys A, Vanderpump M, Yasmin E. Thyroid dysfunction and reproductive health. Obstet Gynecol. Published online January 2015:39-45. doi:10.1111/tog.12161
- 2.Bahar A, Akha O, Kashi Z, Vesgari Z. Hyperprolactinemia in association with subclinical hypothyroidism. Caspian J Intern Med. 2011;2(2):229-233. https://www.ncbi.nlm.nih.gov/pubmed/24024022
- 3.Sarkar D. Recurrent pregnancy loss in patients with thyroid dysfunction. Indian J Endocrinol Metab. 2012;16(Suppl 2):S350-1. doi:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3603072/
- 4.National Institute for Healthcare and Clinical Excellence. Hypothyroidism. NICE. Published August 2020. https://cks.nice.org.uk/topics/hypothyroidism/#!scenario:2
- 5.Wasserman EE, Pillion JP, Duggan A, et al. Childhood IQ, hearing loss, and maternal thyroid autoimmunity in the Baltimore Collaborative Perinatal Project. Pediatr Res. Published online August 23, 2012:525-530. doi:10.1038/pr.2012.117
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