Establishment of a lower cut off to diagnose hypothyroidism in Indian pregnant women

Abstract

Thyroid dysfunction is a common disorder in pregnancy which affects both maternal and fetal outcomes. There are very less and limited data on prevalence of hypothyroidism during pregnancy from India because no such big study done till now. This study done to define cut off value of serum TSH level in Indian pregnant women as hypothyroid and maternal and fetal outcomes. This study was planned to establish a lower cut off value for serum TSH to diagnose hypothyroidism in Indian pregnant women. This is a prospective and retrospective cohort study conducted in a period of 1.5 years between September 2021 to April 2023, in the department of Obstetrics & Gynecology GMC Shahdol in 1000 pregnant women’s who comes in antenatal checkup in OPD.All healthy pregnant women with singleton pregnancy willing to participate in the study were enrolled. Women which have multiple pregnancy, known chronic medical disorder like diabetes, hypertension, any autoimmune disorder with hyperthyroidism or known hypothyroidism, bad obstetric history with a known cause are excluded from study.However, there are few limitations of this study. We have not assessed trimester specific ranges. Follow up beyond newborn period was not possible because after discharge most infants either did not come for follow up or they were seen in pediatric clinic. We did not carry out thyroid examination using ultrasound, and we have not evaluated other causes of hypothyroidism in these women.All pregnant women underwent ELISA TSH assay. Women with serum TSH >6.2mIU/L underwent Free Thyroxin (FT4) estimation and labelled as overt hypothyroid (OH) (group I) or subclinical hypothyroid (SCH) (group II). Women with serum TSH between 3-6.2mIU/L & 0.4-3mIU/L were labelled as group III & control. Foeto-maternal outcomes were compared between group I, II,III & controls. The prevalence of SCH & OH was 6.4% and 3.8%. Pre-eclampsia, gestational DM & IUFD in group I and foetal distress in group II developed in significantly higher number of women (p=0.009, p=0.002, p=0.002 & p=0.004 respectively) Foeto-maternal variables assessed in group III none was significantly different from control group. There is a high prevalence of hypothyroidism and adverse foeto-maternal outcome is more commonly associated with OH as compared to SCH. TSH 3-6.2mIU/L may be taken as normal during pregnancy in the Indian population. We recommend a higher cut off for serum TSH to diagnose hypothyroidism ie >6.2mIU/L in Indian pregnant women. The strong point of this study is that we have included large number of subjects from India. From this study we know the level of thyroid cut off level in Indian pregnant women’s which can be used for diagnosis and treatment of this disorder.