Aim: To evaluate and assess the prevalence along with its related complications of subclinical hypothyroidism in pregnant ladies during the 1st trimester of pregnancy in Pakistani population.

Study design: Cross sectional study

Place and duration of study: Department of Medicine, Unit-1 of Lahore General Hospital, Lahore, Pakistan from 11th February 2019 to 29th December 2019.

Methodology: Four hundred and fifty seven pregnant women with a gestational age up to 12th week with an age group between 18-45 years were included in this study. Blood samples were collected for free triiodothyronine, free thyroxine and thyroid stimulating hormone levels. Patients were regularly followed at an interval of 4 weeks for their entire pregnancy period. Adverse events and complications were noted.

Results: One hundred and sixty nine subjects had TSH levels above the normal range i.e., 4.6-10mIU/L. 288 subjects were having TSH below 4 mIU/L levels. The overall prevalence of subclinical hypothyroidism (SCH) was found to be 37% in pregnant women during their first trimester of pregnancy. Pregnant women having subclinical hypothyroidism (SCH) were having higher risks of loss of pregnancy, abruptio placentae and neonatal death rates as compared to euthyroid pregnant women.

Conclusion: Higher prevalence of subclinical hypothyroidism (SCH) in the first trimester of pregnancy indicates that these women are at increased risks of loss of pregnancy, placental abruption and neonatal death as compared to euthyroid pregnant women.

Keywords: First trimester; pregnancy; subclinical hypothyroidism