Perinatal outcomes, such as preterm delivery, low birth weight and some obstetric complications, are increased significantly after in-vitro fertilization (IVF) compared with spontaneously conceived pregnancies. The degree of difference is greater for singletons than for twins, especially with regard to preterm delivery which is increased two fold in IVF singletons and by 40% in twins. It is difficult to obtain accurate outcome information because of unmeasured confounders such as smoking status and fetal reduction. It is also unknown whether IVF technologies or patient infertility is the major contributor to adverse outcomes. Birth defects are increased, shown in a number of systematic reviews, and there has been a particular interest in imprinting syndromes. Epigenetic modifications may play a larger role in IVF outcomes, as yet unidentified. There is no apparent increase in adverse outcomes in children up to adolescence, although further studies are needed to examine longer-term risks, including those for cancer.