A C-section may be done for reasons related to the health of the mother or baby, or conditions related to the pregnancy or process of labor.
Reasons related to a mother's health that may lead to a C-section include:
Past surgeries involving the uterus. The most common such surgery is a past C–section in the thick part of the uterus, a so-called classical cesarean. These are the minority of cesareans however. And many women can try to deliver a baby vaginally after a previous C-section.
Infection. If a mother has an infection that may be passed on to the baby during a vaginal delivery, that's another case when a C-section would be recommended. In some women with HIV or genital herpes, for example, cesarean delivery may be recommended to minimize the risk of the baby being infected during the course of labor and delivery.
Reasons for cesarean delivery related to the baby's condition include:
Breech position (hips or legs positioned in front of the head)
Multiple gestation (delivering triplets or a greater number of multiples vaginally is complex, especially if all are not head-first)
Evidence that the baby is not tolerating the process of labor (for example, changes in the fetal heart rate with contractions)
Reasons for cesarean delivery related to the pregnancy include:
Abnormal position of the placenta (for example, the placenta covers the cervix, a condition known as placenta previa)
Failure of the cervix to dilate during labor
Failure of the baby to descend through the birth canal during labor and pushing.
C-sections are generally safe. But the risk of major complications during the surgery is higher than with vaginal birth. Some of the increased risk is related to the reason why cesarean delivery was recommended and not related to the procedure itself.
Vaginal birth is preferred over cesarean when labor and the delivery are proceeding without complications.
In some cases, cesarean delivery is clearly appropriate. The use of C-sections sections in these circumstances has made delivery dramatically safer for both mother and child.