Premature Delivery A delivery is considered premature when it occurs before the 37th week of pregnancy. Normal delivery, or full-term delivery, occurs at about 40 weeks after the last normal menstrual period.
Most premature deliveries result from unexpected, premature labor.
However, a premature birth may be induced by the doctor, if a condition exists that could harm the mother or the child, if the baby was allowed to be delivered at full term. Although premature delivery poses very little risk to the mother, it does pose a risk to the infant. Forty percent of all premature births occur for no known reason. Of the known conditions that cause premature labor, pre-eclampsia, which is high blood pressure in the mother, is the most common maternal cause. Also, women whose mothers took the drug DES while they were pregnant with them appear to be at increased risk for early delivery.