Delivery
Babies born too early may have more health problems at birth and later in life than babies born later. Being pregnant 39 weeks gives your baby's body all the time it needs to develop. Your baby needs 39 weeks in the womb because: Important organs, like your baby's brain, lungs and liver, need time to develop.
The contractions help dilate (widen) the opening to the vagina (called the cervix). This allows the baby to move out of your body and be born. First-time moms are usually in labor for about 12 to 18 hours, on average. If you've had a baby before, labor usually goes more quickly, usually about half that amount of time.
Because first-time C-sections often lead to C-sections in future pregnancies, a vaginal birth is generally the preferred method of delivery for first pregnancies. About 2 in 3 babies in the United States are born via vaginal delivery, according to the National Center for Health Statistics.
