Research published in Medical Screening (a British Medical Journal specialty publication, November 22, 2000) examined the relationship between thyroid function and miscarriage risk during pregnancy. The study followed more than 9,000 pregnant women and measured thyroid-stimulating hormone (TSH) levels to identify hypothyroidism.
Key Findings
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Slightly over 2% of the women had TSH levels ≥6, indicating hypothyroidism.
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Among women with TSH above 6, the miscarriage rate was 3.8%—
compared with 0.9% in women with normal thyroid function. -
Miscarriage risk increased as TSH increased.
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Women with TSH above 10 had a miscarriage rate of 8.1%.
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Based on these results, the authors suggested that routine thyroid screening should be part of every prenatal evaluation. Their analysis estimated that six out of ten late miscarriages in the study population could be linked to unrecognized hypothyroidism.
Other Pregnancy-Related Risks
Additional research on pregnant women with hypothyroidism has noted possible associations with:
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Placental abruption
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Premature birth
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Low birth weight
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Pregnancy-related hypertension
However, many of these studies were conducted in high-risk or specialty clinics, meaning the results may not fully represent the general population. More research is needed to clarify these relationships.
How Common Is Hypothyroidism?
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About 1 in 50 pregnant women has thyroid deficiency.
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Nationwide, an estimated 27 million Americans have hypothyroidism (not limited to pregnancy).
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As many as half may go undiagnosed.
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Prevalence increases with age—by age 60, 1 in 5 women may have some degree of thyroid deficiency.
Symptoms can include fatigue, depression, low libido, weight changes, and reduced quality of life. Untreated hypothyroidism may contribute to elevated cholesterol, cardiovascular strain, infertility, and impaired cognitive development in offspring—highlighting the importance of early detection and appropriate care.
Educational only — not medical advice.
