History and Objectives: The present study was carried out to study multifetal birth and factors that influence multifetal gestation at Mahdieh Medical Center in 1992.

Materials and Methods: A descriptive study was carried out on 11775 single and multifetal gestational deliveries. Personal information on women with multiple gestation, methods of contraception, embryonic development, gestational period, weight of embryo and prevalence of multifetal birth and confidence interval (CI) was recorded.

Results: The prevalence of double gestational delivery was 6.2 in thousand (CI 95%) and its prevalence in the population is 5.9-6.7 in thousands. Mean age and average number of pregnancies were 27.7±6.8 and 2.3±1.9 respectively. Double and single oocyte double gestation was 69.4 and 30.6 percent respectively. The prevalence of preterm delivery was 36.6%. Cesarean section was carried out on 14.7% and 51.3% of single and double gestational pregnancies. The prevalence of the underweight (Below 2500 grams) was 49.3% and 50.7% for the first and second twin.

Conclusion: Multiple gestations are considered as high-risk pregnancy due to increased risk to mother and fetus, complication of premature pregnancies and premature infants. Such pregnancies warrant special care during pregnancy in order to reduce probable complications and should be considered as a national priority in order to prevent premature birth and its side effects.