Background: Thyroid disorders are frequent in women of reproductive age, with a major influence on both female reproductive function and fetal development. Pregnancy is associated with profound modifications in the regulation of thyroid function. Women with thyroid dysfunction both overt and subclinical are at increased risk of pregnancy-related complications such as threatened abortion, preeclampsia, preterm labour, placental abruption, and postpartum haemorrhage. Fetal complications include low birth weight, IUGR, neonatal hyperthyroidism, still birth and perinatal mortality. As Assam lies on the foot hills of Himalayas, the prevalence of thyroid dysfunction, as expected, is high in general population including pregnant ladies hence this study is an effort to throw some light in this direction. Methods: This prospective study was conducted enrolling 132(both primipara & multipara), irrespective of the gestational age, attending the antenatal OPD of Gauhati Medical College was enrolled for the study. TSH, free T4, and anti TPO antibody values were assessed. TSH and free T4 was planned to be repeated at necessary intervals according to the results of thyroid function tests in the first visit. At the end, obstetric and perinatal outcome of the pregnancy was noted. Results: In the study, 59.84% had normal thyroid function, 32.57% had hypothyroidism (subclinical in 25% andovert in 7.57%), 6.06% had gestational thyrotoxicosis and 1.51% had Grave’s disease. 28.78%had TPO positivity.In the group with subclinical hypothyroidism, PIH, GDM, preterm delivery, APH, abortion and LSCS were higher compared to the group with normal TSH though not significant. In the group with overt hypothyroidism, IUGR and neonatal jaundice requiring phototherapy were significantly higher compared to the group with normal TSH. Conclusions: Thyroid dysfunction among reproductive age group females is associated with significant adverse effects on maternal and fetal outcome spotlighting the essence of routine antenatal thyroid screening in first trimester.