During the first five years of in vitro fertilisation in the University Hospital of Rotterdam, 158 pregnancies resulted in 118 deliveries of 150 babies. There were 38 clinical abortions and 2 tubal pregnancies. Transfer of multiple embryos to enhance the chance of pregnancy led to a high percentage of multiple pregnancies, 23% of all deliveries. During pregnancy the incidence of vaginal bleeding was high and the number of admissions to a hospital was increased considerably. The percentage of caesarean sections was high because of the large number of multiple pregnancies and possibly because of the 'precious' nature of the pregnancy. There was no indication of more frequent occurrence of congenital abnormalities.