Prevalence of subclinical and undiagnosed overt hypothyroidism in a pregnancy loss clinic

Recent studies have associated pregnancy loss with subclinical hypothyroidism, defined as elevated thyroid-stimulating-hormone level, with normal free thyroxine. In overt hypothyroidism, the free thyroxine is low. Subclinical and overt hypothyroidism occurs in 0.25-2.5% and 0.2-0.3% of pregnancies respectively. We examined the prevalence of subclinical and undiagnosed overt hypothyroidism in women with recurrent miscarriage, late miscarriage and stillbirth attending the Pregnancy Loss Clinic. Data was collected from the Pregnancy Loss Clinic records. Women with sporadic miscarriages, autoimmune disorders, thrombophilias and known hypothyroidism were excluded. Two-hundred-and-sixty-two women were included. Median maternal age was 35 years (range 18-47). Subclinical and undiagnosed overt hypothyroidism was found in 11.45% of women. Twenty-two women (8.39%) had subclinical hypothyroidism, eight (3.05%) had undiagnosed overt hypothyroidism. Results were compared to women with ongoing pregnancies. A proportion of women attending the clinic had subclinical or undiagnosed overt hypothyroidism, raising the suspicion of causation in unexplained pregnancy loss.