These are twins that develop from two separate ova which were fertilized at the same time. They do not necessarily have come from the same ovary. The incidence of binovular twins increases with maternal age, reaching a peak between 35 and 39 years.
They are no more similar to each other than to other members of the family.
Non-identical twins never share the same amnion, chorion or placenta. There may be, however, fusion of separate placentae.
The incidence of binovular twins is three times that of uniovular twins.
Last reviewed 01/2018