Background:The aim of the present study was to determine the effect of various perinatal factors on cord blood TSH among newborns in Isfahan, Iran.Materials and Methods:This was a descriptive–analytic cross sectional study which performed in Isfahan Iran. During a period of four months, since February to May 2012 a total number of 440 newborns delivered in Alzahra and Shahid beheshti hospitals were enrolled in the study. For all newborns one mL blood sample from umbilical vein was obtained by one of the project investigators and sent to laboratory for further examinations. Cord blood TSH and birth body weight (BBW), gestational age, history of gestational diabetes mellitus (GDM), apgar at one minute, apgar at five minute, newborn gender and the mother's age were documented. Differences considered statistically significant if P < 0.01.Results:440 newborns enrolled in the study, 221 (50.2%) were male and 219 (49.8%) were female. Among study parameters, method of delivery had statistically significant relation with cord blood TSH (P < 0.001), and other factors such as BBW, gestational age, GDM, apgar at one minute, apgar at five minute, newborn gender and the mother's age didn’t have statistically significant relationship with cord TSH level.Conclusion:In conclusion we deduce that the only factor that can affect cord blood TSH was method of delivery. Infant with vaginal delivery has higher TSH level in cord blood. Other factors that were evaluated in this study didn’t have any statistically significant relationship.