Thyroid dysfunction in pregnancy and its feto-maternal outcome: a prospective observational study

Background: Thyroid disorders constitute the most prevalent endocrine abnormality encountered during pregnancy, with well-documented potential for significant adverse effects on both maternal and fetal health. Physiological adaptations unique to gestation alter thyroid hormone economy, making diagnosis and interpretation of thyroid function tests particularly challenging in this population. The burden of undetected thyroid dysfunction in pregnant Indian women remains incompletely characterised, with most available evidence derived from non-Indian cohorts. Methods: This prospective observational study enrolled 150 antenatal women attending the Department of Obstetrics and Gynaecology, Dr. D.Y. Patil Hospital, Nerul, Navi Mumbai, over 16 months (March 2023–June 2024). Thyroid function tests (T3, T4, TSH) were performed each trimester using chemiluminescent and ELFA techniques, with trimester-specific TSH reference ranges as per the 2011 American Thyroid Association guidelines. Maternal and feto-neonatal outcomes were documented at delivery. Results: The prevalence of thyroid dysfunction was 28%, with hypothyroidism accounting for 25.3% (overt 8.7%, subclinical 16.7%) and hyperthyroidism for 2.7%. Thyroid dysfunction was significantly associated with preterm delivery (p=0.001), low birth weight (p=0.001), and lower APGAR scores at 1 minute (p=0.015) and 5 minutes (p=0.001). Higher rates of NICU admission (p=0.012), stillbirth, IUGR, abortion (p=0.004), and miscarriage (p=0.006) were observed in women with thyroid disorders. No significant associations were found with maternal age (p=0.969) or mode of delivery (p=0.686). Conclusions: Thyroid dysfunction in pregnancy carries a significant burden of adverse feto-maternal outcomes. The high observed prevalence underscores the need for universal thyroid function screening in early pregnancy and the pre-conceptional period to enable timely detection and management.