What are the specific risks that come along with twin pregnancy or multiple gestation? As a perinatologist and a father of twins, I am very familiar with the potential risks of a twin pregnancy, and again, they come in maternal risks and fetal risks. Some of the maternal risks of twin pregnancy include things like excessive weight gain, diabetes, pre-eclampsia, and some of the fetal risks of multiple gestation are even greater than that. We can start with some of the simple things like twins are at a higher likelihood of delivering early, twins on average deliver at about 35 weeks compared to singleton pregnancies, in which nine out of ten deliver at at least 37 weeks. If you have triplets, that number drops to 32 weeks, and if you have quadruplets it drops to about 29, and if you have quintuplets, that is five, it drops to about 27 weeks. So early delivery is one of the very well recognized risks of twin pregnancy. Some of the other risks are a little bit more complicated, and they have to do with the twins not growing evenly, or not sharing their blood supply evenly, in identical twins who have a common blood supply at the level of the placenta. That can lead to differential growth, but it can even lead to a condition that's fairly complicated, called twin transfusion syndrome in which one twin literally acts as a donor, a blood donor, and another twin acts as a blood recipient. That condition has an extremely high rate of fetal loss. In some circumstances the procedure that can be used to treat twin transfusion syndrome can result in survival of both twins in as many as 70% of cases, and in survival of one twin in more than 90% of cases.