Marked changes in maternal thyroid activity occur in pregnancy and during labor. The present study investigates the effect of labor on thyroid function and the role of thyroid hormones during this process. Materials and Methods: Thyroid function was studied in 64 pregnant primigravida women. The study group comprised of 32 full term pregnant women scheduled for spontaneous vaginal delivery, while the control group included 32 pregnant women at around 32 weeks of gestation. Serum total T3 (TT3), total T4 (TT4) & thyrotropin (TSH) were estimated by high-sensitive radioimmunoassay. In the study group, blood samples were obtained during various phases of labor; Phase A: onset of labor; Phase B: within 2 hours of delivery of placenta and membranes and phase C: 24-48 hours after delivery (immediate puerperium). Results: Mean age of the study group was 23.46±3.07 years, and that of controls was 23±2.8 years. In Phase A, serum TT3 & TSH levels were significantly higher than in controls [1.479±0.52 vs 1.248±0.3 ng/mL & 3 (0.9-6.5) vs 1.2 (0.4-3) μIU/mL respectively; P< 0.05]. In Phase B, there were fall in levels of TT3, TT4, but TSH decreased significantly [1.8(0.6-6) vs 3 (0.9-6.5) μIU/mL; P< 0.05]. In Phase C, TT3 showed significant fall [1.117±0.39 vs 1.421±0.4 ng/mL; P< 0.05]. Conclusion: All the values of thyroid function test were within normal range in controls & study group in all phases. All alterations, the significant rise in TT3 in Phase A, and the fall in phase C and the significant rise in TSH in Phase A and the fall in Phase B, seen during labor seemed to be need based and was significantly influenced by stress present during labor.
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