The increased risk of complication observed in singleton pregnancies resulting from in-vitro fertilization (IVF) does not seem to be related to the IVF method itself.

Singleton pregnancies resulting from in-vitro fertilization (IVF) seem to have an increased risk of obstetric and paediatric complications. In a retrospective study we compared, during the same period, 162 IVF singleton pregnancies with 263 pregnancies resulting from stimulated cycles (without IVF) and with 5096 natural pregnancies. No significant difference was found between the first two groups concerning complications (i.e. prematurity, low birthweight, small-for-gestational-age and perinatal mortality). The results indicate that an adverse outcome is more common for pregnancies after ovarian stimulation (with or without IVF) compared to natural pregnancies. Therefore the increased risk does not appear to be linked to the IVF method itself but rather to a common factor in these two populations, i.e. population characteristics, underlying infertile status and/or ovarian stimulation.