Obstetric outcome of natural and assisted conception twin pregnancies is similar

Background. The risk of obstetric intervention and adverse fetal or neonatal outcome is considerably higher in multiple gestation than in singleton pregnancy. How assisted conception influences obstetric management and outcome in twin pregnancies has not been evaluated. Methods. A survey of all twin pregnancies in Iceland and the Tayside Region, Scotland for a four year period, 1990-93, comparing twins after assisted fertilization with natural conception. Results. The total number of twin pregnancies was 522, of which 453 were natural conceptions and 69 assisted. The twin rate was 1:75 among natural conceptions, but 1:5 in women having assisted fertilization. Mean gestational age in both groups was 36 weeks. Elective Cesarean section was used more often in the assisted conception group (odds ratio 2.57; p=0.003). Induction rates did not differ to any significant degree and once labor commenced, no difference was seen between assisted and natural conception twins in the mode of delivery or neonatal short term morbidity. Birthweight, gestational length and perinatal mortality rates by conventional and extended classification were not different. Conclusion. After allowing for more frequent elective Cesarean section in the obstetric care of the assisted conception pregnancies, there was no major difference in obstetric and neonatal management or outcome between twins resulting from natural and assisted conception.