Abstract

Hypothyroidism (insufficient production of thyroid hormone) has long been associated with an increased risk of pregnancy loss. More recently, a pre-clinical state of hypothyroidism known as subclinical hypothyroidism has been linked to pregnancy loss. We sought to test the hypothesis that abnormal thyroid function, in particular an underactive thyroid is associated with pregnancy loss. We reviewed thyroid function in 262 women with recurrent miscarriage, late miscarriage and stillbirth who attended the pregnancy loss clinic and compared their results to women with ongoing pregnancies. In our study we found the incidence of subclinical hypothyroidism and hypothyroidism was 8.4% and 3.1%. respectively. Compared to the general population, these incidence rates are about 4 times higher for subclinical hypothyroidism and about 10 times higher for hypothyroidism. This raises the suspicion that hypothyroidism is a factor in unexplained pregnancy loss. Our findings support a policy of universal screening of women for thyroid function in early pregnancy with subsequent treatment of abnormal thyroid function.