Identical (monozygotic) twins develop from a single egg-sperm combination that splits into two. If the split is delayed, usually a week or so after conception, the processes of growing a placenta, ...

The birth of twins has always fascinated people. Throughout history, twins have been seen as special, sometimes even magical. Today, medical science helps us understand the different types of twin ...

As mothers get older and assisted conception becomes more common, the incidence of multiple births--primarily of nonidentical siblings, but also of identical ones--has dramatically increased. Multiple ...