Prevalence of Subclinical Hypothyroidism in First-Trimester Pregnancy: A Cross-Sectional Study at a Tertiary Care Hospital in West Bengal

Background: Thyroid dysfunction is one of the most frequent endocrine abnormalities that may occur during pregnancy, and has important implications for both maternal and foetal outcomes. Subclinical hypothyroidism (SCH) — This is when someone has an elevated thyroid-stimulating immunoglobulin (TSH) level, but the serum level of free thyroxine (FT4) is normal, and it is often not detected unless biochemical screening is carried out regularly. It is especially important to identify early (first trimester) due to the high sensitivity of fetal neurodevelopment to maternal thyroid hormone status early in gestation. The aim is to determine the prevalence of subclinical hypothyroidism among adult first-trimester pregnant women attending a tertiary care hospital in West Bengal. Material and Methods: A hospital-based cross-sectional study was conducted among first-trimester antenatal women (8–12 weeks of gestation) attending a tertiary care hospital in West Bengal. Thyroid function was assessed using serum FT4 and TSH estimation. Pregnant women aged below 18 years were excluded. A total of 282 pregnant women were included in this study. Subclinical hypothyroidism was defined as elevated serum TSH (>2.5 µIU/mL) with normal FT4 levels. Results: The mean age of participants was 24.25 ± 4.38 years. The mean serum FT4 level was 1.09 ± 0.24 ng/dL, while the mean serum TSH level was 3.38 ± 5.81 µIU/mL. Most participants belonged to the 21–25 years age group (43.6%). Subclinical hypothyroidism was identified in 88 participants, yielding a prevalence of 31.2%.. Conclusion: A considerable proportion of first-trimester pregnant women demonstrated subclinical hypothyroidism. These findings support the importance of routine thyroid function screening during early pregnancy for timely diagnosis and management.

Keywords: Subclinical hypothyroidism, pregnancy, first trimester, thyroid-stimulating hormone, free thyroxine, antenatal screening, West Bengal.