TPO and autoimmune thyroid disease: With a prevalence of up to 18% in pregnant women, positive thyroid autoantibodies are associated with a higher risk of premature delivery.32 Nonetheless, Benhadi and colleagues33 found an association between high thyrotropin levels and spontaneous abortion and fetal or neonatal death after adjustment for thyroid peroxidase antibody status, suggesting that the influence of maternal thyrotropin levels on risk of adverse pregnancy outcomes cannot be obscured by thyroid autoimmunity.