Publication:

Maternal urinary iodine status during antepartum and postpartum periods and its association with neonatal TSH: a hospital-based study from eastern India

Background Iodine requirement increases during pregnancy and early postpartum, and inadequate iodine intake may adversely influence neonatal thyroid function. Region-specific data from eastern India remain limited. Objective was to assess maternal urinary iodine concentration (UIC) during antepartum and postpartum periods and evaluate its association with neonatal thyroid-stimulating hormone (TSH).

Methods This hospital-based prospective observational study (December 2024 to April 2025) included 70 mother-neonate dyads. Maternal midstream urine samples were collected during antepartum and postpartum periods, and UIC was measured using the Sandell-Kolthoff method. Neonatal screening samples were obtained on day 3-5 of life, and TSH and free T4 (fT4) were measured by chemiluminescent immunoassay. Maternal iodine status was categorized using WHO pregnancy cut-offs. Associations between maternal UIC and neonatal thyroid parameters were evaluated using Spearman’s correlation. Receiver operating characteristic (ROC) analysis was performed to assess the ability of maternal UIC to predict neonatal TSH >5 mIU/l.

Results Mean antepartum and postpartum UIC were 255.6±78 µg/l and 249.6±82 µg/l, respectively. Iodine deficiency ( 5 mIU/l (AUC=0.830) at a cut-off of 222.8 µg/l (sensitivity 69.7%, specificity 94.6%).

Conclusions Maternal UIC during both antepartum and postpartum periods is inversely associated with neonatal TSH, highlighting the influence of maternal iodine status on neonatal thyroid function. Despite overall iodine sufficiency, a subset of mothers remained iodine-deficient, underscoring the need for continued monitoring of iodine nutrition during pregnancy and early postpartum.