National status of testing for hypothyroidism during pregnancy and postpartum

Abstract

Context: Hypothyroidism, overt or subclinical, is associated with adverse outcomes for pregnant women and their offspring. Knowledge of current national thyroid testing rates and positivity during pregnancy is limited. Objective:Theaimof the studywasto estimate thyroid testing rateandpositivity during pregnancy and postpartum, including testing and positivity rates of thyroperoxidase antibody (TPO Ab) and free T 4 tests in pregnant women with elevated TSH levels (hypothyroid), and in pregnant women having TSH within range (euthyroid). Design and Setting: Records from a large, national sample of pregnantwomenscreened from June 2005 through May 2008 were examined. Participants: The study included 502,036 pregnant women, for whom gestational age information was available. Main Measures: Testing rates and the prevalence of hypothyroidism during pregnancy and postpartum were measured using assay-specific, trimester-specific reference intervals. Screening and positivity rates of TPO Ab and free T 4 tests were also measured. Results: Of women ages 18 to 40 yr, 23% (117,892 of 502,036) were tested for gestational hypothyroidism (defined as both subclinical and overt hypothyroidism). Of these, 15.5% (18,291 of 117,892) tested positive for gestational hypothyroidism. Twenty-four percent (22,650 of 93,312) of women with TSH within range and 33% (6,072 of 18,291) of women with elevated TSH were also tested for gestational hypothyroxinemia. Gestational hypothyroxinemia was seen in 0.2% (47 of 22,650) of the tested women with TSH within range and was seen in 2.4% (144 of 6,072) of the tested women having elevated TSH; 0.3% (276 of 93,312) of women with TSH within range received a TPO Ab test, and of these, 15% (41 of 276) tested positive; 0.66% (120 of 18,291) of women with elevated TSH received a TPOAb test, and of these, 65%(78 of 120) tested positive. Only 20.7%(1873 of 9063) of hypothyroid women received thyroid screening within 6 months postpartum; of these, 11.5% (215 of 1873) were diagnosed with postpartum hypothyroidism. Conclusion: Gestational hypothyroidism is more common than generally acknowledged. Testing is not common, and test selection is variable. There is a low rate of postpartum follow-up. Copyright © 2012 by The Endocrine Society.