RESUMO
The increase in the rate of multiple pregnancies in Australia in recent years is primarily due to the use of assisted reproduction technology. Compared to singleton births, fetal, neonatal, and perinatal mortality rates are 3-6 times higher in twins and 5-15 times higher in multiple births of a higher order. Cerebral palsy rates among survivors are six times higher in twins and twenty times higher in triplets. The increased risks in multiple pregnancies are not entirely explained by their higher prematurity and low birthweight rates. In Australia, the practice of transferring more than three embryos in any one assisted reproduction technology cycle has declined in recent years and, as a result, the number of multiple pregnancies from assisted reproduction technology has also declined. Nevertheless, assisted reproduction technology pregnancies remain to have poorer than normal outcome with regards to spontaneous abortion, ectopic pregnancy, preterm birth, low birthweight, and perinatal mortality. Infants born after assisted reproduction technology have a higher neonatal morbidity rate, including a greater requirement for assisted ventilation, and a higher long-term neurodevelopmental disability rate. These adverse outcomes following assisted reproduction technology are partly due to the increased risk of multiple pregnancy and partly due to preterm and low birthweight. This fact and the lack of evidence that the transfer of more than two embryos improves pregnancy rates, make it advisable to limit the number of embryos transferred to no more than one or two per cycle.