The rate of multiple pregnancies is showing a significant increase in Western countries. Twin gestations should be considered a high-risk condition because they are responsible for a disproportionate amount of overall perinatal morbidity and mortality. We used a specialised ultrasound protocol based on chorionicity to monitor 44 twin pregnancies (61% dichorionic diamniotic (DD) and 39% monochorionic diamniotic (MD)). Adverse pregnancy outcomes and pre-term deliveries were more common in MD pregnancies than in DD pregnancies; the rate of extreme pre-term delivery (