Context: Thyroid dysfunction in early pregnancy is associated with a number of adverse outcomes. Furthermore, the presence of thyroid autoantibodies has been associated with an increased risk of miscarriage.
Objective: To determine the prevalence of thyroid autoantibodies and their effect on thyroid function tests in an unselected population of women in early pregnancy.
Design and setting: Cross-sectional study of samples that were collected for aneuploidy screening between 10 and 14 weeks gestation in Northern Sydney Area Health Service. Thyroid function tests (free T3, free T4 and thyroid-stimulating hormone) and thyroid autoantibodies to thyroperoxidase and thyroglobulin were measured.
Patients and methods: Thyroid function tests were performed on a random sample of 257 blood samples.
Results: The presence of thyroid autoantibodies was common (18.3%) and was associated with subtle changes in thyroid function consistent with impaired thyroidal reserve.
Conclusions: The prevalence of antithyroid Abs in an unselected pregnant population in the late first trimester was about 18%.