If you have experienced a miscarriage you may want to take a closer look at the finer detail of your thyroid health. Thyroid wellness is commonly assessed with a TSH (thyroid stimulating hormone) test and research has demonstrated that TSH values which are in the upper half of the normal reference range - above 2.5 mIU/ml may reflect an increased risk for miscarriage. Therefore, your TSH value may diagnosed as being 'normal' while also reflecting a potential for increased miscarriage risk due to the continued use of the out-dated TSH reference range which many physicians still use. Many progressive physicians now consider 2.0 or 2.5 mIU/ml the upper cut-off for TSH normalcy especially in women who are trying to conceive.

An Italian study - published in Human Reproduction, 2011 - has further explored the link between thyroid dysfunction and miscarriage and has discovered that even when a woman’s TSH value is below the new accepted norm for pregnancy - 2.5 mIU/ml - women with a history of miscarriage may benefit from a 'thyroid stress-test' to check in on how well their thyroid adapts to stimulation. Thyroid stimulation mimics the demands of pregnancy; an inability to create a surge of extra thyroid hormones in very early pregnancy could be a hidden trigger for pregnancy loss.

The thyroid gland has to perform a rather remarkable feat shortly after conception: a sharp and timely uptick in thyroid hormone production is necessary both to sustain pregnancy and to protect early neurological development. It is though that some women who experience recurrent miscarriage may simply have trouble adapting to the hormonal demands of pregnancy, specifically, they may be unable to produce the dramatic boost in thyroid hormone production which is required in the early weeks of gestation. Because thyroid testing is seldom performed at this critical time, any maladaptation will usually fly under the radar and be undiagnosed. As these astute Italian researchers clearly note:

"Proper maternal thyroid function is necessary for a successful pregnancy."

This innovative study sought to assess how well the thyroid responds to an increased demand for thyroid hormones by stimulating the thyroid to boost it's output with a thyrotrophin-releasing hormone (TRH) test. The study investigated the ratio between baseline and peak thyroid stimulating hormone (TSH) twenty minutes after stimulation with thyrotrophin-releasing hormone (TRH)] in 463 women with unexplained recurrent miscarriage (RM) who had normal TSH values.
Women with recurrent miscarriage tended to have higher - although perfectly normal - baseline TSH values compared to controls whose average TSH values were 1.3 μIU/ml. The researchers developed a novel model for assessing transient thyroid impairment from the TRH test and suggest that:

"A transient impairment of thyroid function in early pregnancy may cause an inadequate adaptation to the increased thyroid requirement and may be implicated in RM (recurrent miscarriage)."

"The evaluation of the proposed iTSHa index, if validated in a larger cohort of patients, may provide information useful to identifying a subset of healthy women, without evidence of thyroid dysfunction or autoimmunity and a TSH in the low-normal reference range, who may be at risk of RM."

Until this test is fully developed, ask your physician for a TSH test as soon as you conceive to check whether your TSH has elevated - above 2.5 mIU/ml - due to the demands of pregnancy. Timely intervention with thyroid hormone replacement may be able to prevent miscarriage if you are experiencing pregnancy loss simply because your thyroid is unable to adjust to pregnancy successfully. Ideally your TSH should be re-checked 4-6 weeks after a dose change or initiation of therapy to check that your TSH has been sufficiently corrected.


This article is for purely informational purposes and is not intended to diagnose or to replace medical or dietetic advice for which you should consult a physician or dietitian.

Human Reproduction, Volume 26, Issue 6, (June 2011), p. 1324-1330
ISSN: 0268-1161, DOI: 10.1093/humrep/der069
Oxford University Press

Prediction of early pregnancy maternal thyroid impairment in women affected with unexplained recurrent miscarriage
Dal Lago, Alessandro1; Vaquero, Elena2; Pasqualetti, Patrizio3; Lazzarin, Natalia4; De Carolis, Caterina5; Perricone, Roberto6; Moretti, Costanzo7