30-41%
** Uterus septus 45.8%
** Leiomyoma uteri 9-20%
** Spinal cord injury 10%
** Carriers of Duchenne muscular dystrophy 17%
*Combination of two medical entities:
** First twin in uterus with two bodies 14.29%
** Second twin in uterus with two bodies 18.52%.

Also, women with previous caesarean deliveries have a risk of breech presentation at term twice that of women