Are there risk factors for a twin pregnancy?

The probability of a pregnancy with more than one baby occurring, that is, a multiple pregnancy, can be affected by heredity. If the woman has a history of multiple pregnancies, there is a greater probability of it repeating. In addition, the woman's age also increases the rate of multiple pregnancies, as does having a high body mass index.

Although it is becoming less common, fertility treatments are also associated with a high percentage of multiple pregnancies. Similarly, taking birth control pills for long periods of time could also be related to a greater probability of a twin pregnancy.