Background: Current guidelines differ between an aggressive case finding approach versus testing only symptomatic women or those with a history of thyroid disease or other associated medical condition. Thus, the aim of this work was to assess the prevalence of subclinical hypothyroidism (SCH) among women attending the outpatient obstetrics and gynecology clinic for their 1st antenatal care visit in 1st trimester. The ultimate goal was to determine whether routine thyroid-stimulating hormone (TSH) testing during the booking visit of antenatal care is indicated or not.

Methods: This cross-sectional observational study was conducted on 104 pregnant women (gestational age ≤12+0 weeks). Participants underwent detailed history-taking, physical examination, and ultrasonography to confirm gestational age. Blood samples were collected to assess TSH levels. Free serum thyroxin (T4) levels were measured only in cases with abnormal TSH values (≥2.5 mIU/L).

Results: Among the 104 participants, 15 (14.4%) had elevated TSH levels, 7 (6.7%) had low TSH levels, and 82 (78.8%) had normal TSH levels. Free T4 analysis in SCH cases showed that 92.85% had normal free T4 levels, while 7.14% had low free T4 levels. No significant associations were found between SCH and demographic factors, gestational age, gravidity, parity, iodine intake, or medical comorbidities. Logistic regression analysis confirmed no significant predictors for SCH

Conclusions: The prevalence of SCH among pregnant women in the first trimester attending Sohag University Hospital outpatient clinic is relatively high (14.4%) and is 1.5 to 5 folds more than other communities. Routine SCH screening in the first trimester might be considered.