About 70 to 80 per centum of the cases are in primiparous women.
primipara pri·mip·a·ra (prī-mĭp'ər-ə)
n. pl. pri·mip·a·ras or pri·mip·a·rae (-ə-rē')
A woman who is pregnant for the first time.
A woman who has given birth for the first time to an infant or infants, alive or stillborn.