Prevalence, associated risk factors and effects of hypothyroidism in pregnancy: a study from north India

There is a controversy regarding universal versus targeted screening for hypothyroidism during pregnancy. We studied the prevalence and the associated risk factors of hypothyroidism. The secondary objective of the study was to compare the maternal and perinatal outcomes in overt and subclinical hypothyroidism.

We screened 1,005 antenatal patients for hypothyroidism with a thyrotropin assay. Patients diagnosed with hypothyroidism were further tested for anti-thyroid peroxidase antibodies and free thyroxin to determine the cause and type (overt or subclinical) of hypothyroidism. Maternal and perinatal outcomes were compared in the overt, subclinical and euthyroid groups.

The overall prevalence of hypothyroidism was 6.3% (overt 2.9% and subclinical 3.4%). Thirty-four (3.4%) new hypothyroid cases could be detected by universal screening. The risk factors for thyroid dysfunction were not significantly different in the screen-positive versus screen-negative patients except for excessive weight gain (p = 0.00). Targeted screening could have missed one third of subclinical hypothyroid cases. Gestational hypertension was significantly greater in the overt hypothyroid group (p = 0.007), and more patients required induction in this group (p = 0.013) but other maternal complications and perinatal outcomes were similar.

We recommend universal screening for hypothyroidism in pregnancy in our population, as the prevalence of hypothyroidism is high.