Introduction: Pregnancy is a physiological state in which significant changes in thyroid function occur. Several factors contribute to these changes. These factors could contribute to thyroid dysfunction during pregnancy especially when a deficiency of iodine intake exists and when thyroid reserve is not sufficient.Aim: To assess thyroid function tests during pregnancy.Subjects and methods: cross-sectional study was carried out on 100 pregnant women attending obstetrics outpatient clinic in Suez Canal university hospitals were invited to enroll in the study. At end of study, the blood samples were assessed for free T3, free T4 and TSH.Results: Our study revealed that most of pregnant women had normal thyroid functions (51%), while subclinical hypothyroidism (39%) was the most prevalent disorder followed by clinical hypothyroidism (6%) and isolated hypothyroxinemia (4%). Conclusion:The most prevalent pattern of thyroid dysfunction in pregnant women was subclinical hypothyroidism.