Some cesarean deliveries are planned ahead of time; others are done when a quick delivery is needed to ensure the mother's and infant's well-being.

Planned cesarean

Some cesarean sections are planned when a known medical problem would make labor dangerous for the mother or baby. Medical reasons for a planned cesarean may include:

• A fetus in any position that is not head-down (including breech position). For more information, see the topic Breech Position and Breech Birth.
• Decreased blood supply to the placenta before birth, which may lead to a small baby.
• The medical need to deliver and no success with inducing labor.²
• Estimated fetal size of over 9lb to 10lb or more.
• A maternal disease or condition that may be worsened by the stress of labor, such as heart disease.
• A placenta that is blocking the cervix (placenta previa). For more information, see the topic Placenta Previa.
• Open sores from active genital herpes near the due date, which can be passed to the fetus during vaginal delivery.
• Infection with the human immunodeficiency virus (HIV), which can be passed to the fetus during vaginal delivery.³
• Multiple pregnancy. The direction and size of the incision depends on the position of the fetuses. In particular, cesarean delivery may be needed for multiple births involving:
  • Twins that share one amniotic sac (monoamniotic twins), because of the risk that the cords will get tangled.
  • Three fetuses or more.
  • Conjoined (Siamese) twins.
  • An overstretched uterus that cannot contract adequately during labor (uterine inertia), making labor prolonged and difficult.
  • Poorly positioned or large fetuses.

Many cesarean deliveries are planned ahead of time for women who have had a cesarean in the past. Medical reasons for a planned repeat cesarean may include:

• A current problem that has led to difficult labor and cesarean before, such as a narrow pelvis and a large fetus (cephalopelvic disproportion).
• Factors that increase the risk of uterine rupture during labor, such as having a vertical scar, three or more cesarean scars, triplets or more, or a very large fetus thought to weigh 9lb to 10lb or more. For more information, see the topic Vaginal Birth After Cesarean (VBAC).
• No access to constant medical supervision by a cesarean-trained doctor during active labor, or no available facilities for an emergency cesarean.

Should I have a VBAC trial of labor after a previous cesarean section?

Emergency cesarean

Some cesarean sections are done without planning, after labor has started. Medical reasons for an emergency cesarean may include:

• Fetal distress (suggested by a very rapid or very slow heart rate)
• Placenta abruptio, which can cause excessive bleeding (hemorrhage) and decreased oxygen supply to the fetus. For more information, see the topic Placenta Abruptio.
• Umbilical cord problems that decrease or cut off fetal blood supply, as when the cord has slipped into the birth canal ahead of the fetus, and the fetus moves into the birth canal and presses against the cord (cord prolapse).

Other reasons you might need a cesarean

• Difficult, slow labor (dystocia)
• Labor that has stopped completely (failure to progress)
• Cephalopelvic disproportion, a combination of the fetus having a large head and the mother having a narrow pelvic structure. This condition is often linked to failure to progress or dystocia.