This chapter deals with perinatal outcomes, i.e. outcomes of pregnancies that have surpassed the early hurdles and have evolved far enough to result in a birth, internationally defined as the separation from its mother of a fetus weighing 500 g or more. Assisted reproductive technology (ART) involves a whole gamut of interventions, used either as a single intervention or in combination, to address alleged dysfunction of one or more of the four crucial elements needed to achieve a successful pregnancy. A large number of studies of pregnancy outcome after ART provide data on small for gestational age (SGA), usually defined as a birth weight below the 10th centile of weight for gestation. The first indication that the perinatal outcome of singleton pregnancies is worse after ART than after natural conception dates back nearly 25 years.