The father does not carry the gene for non-identical twins, as releasing more than one egg at a time is a trait that runs in the maternal line. There is no evidence suggesting that identical twins run in families. Women who experience a multiple pregnancy are at higher risk of certain complications.
Hyperovulation, which is the tendency to release more than one egg during ovulation, is influenced by genetics. In addition, there are non-genetic influences. Women who have already had children are more likely to have them. Older women are more likely to release more than one egg, until they move past the age of 35. As infertility treatment causes the body to produce more than one egg at a time, it too increases the chance of having twins. In addition, women of African descent are more likely to experience multiple pregnancies.
Although some people believe multiple pregnancies skip a generation, there is no evidence to support this. Even if there is a genetic tendency to produce twins in the male line, a man's sperm cannot influence how his partner ovulates.
While most women who have a multiple pregnancy progress healthily, some are at higher risk of complications. This includes gestational diabetes, preeclampsia, preterm labor and genetic defects.