Why Are Cesareans Performed?

Why Do Doctors Do Cesareans?

There are a number of reasons why a doctor may choose to perform a cesarean delivery. Cesarean sections fall into two broad categories: primary cesareans, which are the mother's first cesarean, and repeat cesareans, which are second or subsequent cesareans.

Cessation of Labor

Failure to progress in labor is the most common indication for performance of cesarean section. There are two main incidents that can cause the suspension of labor: the mother's cervix may stop dilating or, after the cervix has completely dilated, the baby may fail to descend through the birth canal. The question is how long to wait for the cervix to dilate or for the baby to descend through the birth canal before performing a cesarean section.

After a mother has reached the active phase of labor (her cervix has dilated more than 4 centimeters), if cervical dilation fails to progress for a period of two hours or more while the mother continues to have adequate uterine contractions, the diagnosis of arrest of dilation is made and a cesarean section should be performed. For first-time mothers, cesarean delivery should be considered after two hours of pushing (or three hours if she has had an epidural); for mothers who have previously delivered vaginally, cesarean should be considered after about one hour of pushing (or two hours if she has had epidural). Cesarean delivery is indicated unless the doctor feels the fetus can be safely delivered with vacuum and forceps.

A cesarean section for failure of labor to progress can be an extremely disappointing experience for a mother who has gone through hours of labor. Since cesarean section is a rather routine procedure for most obstetricians, patients often fail to realize that without intervention a true arrest in labor could result in the death of both mother and fetus. Without performance of a cesarean section, such women would continue an ineffective labor until their baby dies and their uterus ruptures or they develop a fatal infection. These situations are not uncommon even today in third-world countries where women do not have access to safe cesarean section intervention. Thus, despite the often disappointing or routine nature of this operation, its ability to ensure a normal productive life for a mother and her child makes it one of the most valuable operations in American medicine today. Without a doubt, more lives have been saved by cesarean section for labor arrest than probably any other operation in the history of medicine.

Fetal Distress

Fetal distress generally refers to the detection of an abnormal fetal heart rate pattern either by listening with the stethoscope (auscultation) or by monitoring of fetal heart rate tracings. Electronic fetal heart rate monitors produce tracings of the fetal heart rate and are discussed in another section. Monitoring of the heart rate is a good way of telling if the baby is doing well during labor. Unfortunately, fetal monitoring is not as good at telling which fetuses are doing poorly during labor. In fact, in a large study of fetuses that showed fetal heart rate patterns that were felt to represent fetal distress, only 0.5% actually ended up with neurologic damage later in life. For this reason, the of Obstetrics and Gynecology has stated that this term is imprecise and not specific and can mean different things for different people. Therefore, more detailed and reliable terms should be used, such as non-reassuring fetal status, or a description of the specific findings that are of concern to the doctor.

Scientists worked on the development of fetal monitoring thirty years ago with the hope that the ability to detect fetal distress would lead to a rapid elimination of cerebral palsy (a condition which is occasionally caused by events during labor and delivery). Unfortunately, thirty years and almost 100 million cesarean sections later, the rate of cerebral palsy in the has not decreased at all. This fact has led to the realization that most cases of cerebral palsy have more to do with abnormal development and less to do with damage that occurs when the fetus is showing signs of distress, keeping in mind that these supposed signs of distress are very unreliable.

Nevertheless, the fetal heart rate monitor remains a very valuable tool for avoiding stillbirth during labor and delivery. While most heart rate patterns do not accurately predict which fetuses are in trouble, other patterns allow the obstetrician to be almost certain that unless she intervenes, death or fetal damage will ensue. Thus, cesarean section for non-reassuring fetal status remains an essential part of obstetrical practice today. At least half of all primary cesarean sections are done either exclusively or partially for non-reassuring fetal status. Because true fetal hypoxia can be diagnosed for certain only after delivery, some doctors today use the term non-reassuring fetal heart rate tracing to indicate what had previously been referred to as fetal distress.

Fetus in the Wrong Position (Malpresentation)

Ideally, babies descend through the birth canal headfirst. Sometimes, however, they present in other positions.

Positions other than head down are called malpresentation. The most common of these abnormal positions occurs when the baby's bottom or feet are toward the mother's birth canal. This position is called breech presentation. Breech presentation poses a number of potential hazards during vaginal delivery. First, the umbilical cord may be pinched or may fall completely out of the uterus and into the birth canal before delivery. When the cord hangs into the vagina before birth it is called cord prolapse. If this happens, the fetus's blood supply is rapidly cut off and emergency cesarean delivery is critical; even then it may not be possible to deliver the fetus soon enough to avoid death or brain damage.

An even worse complication of breech delivery is what is called an entrapped head. In most term pregnancies the baby's head and body are about the same size. This means that if the head delivers first without problems, the body is almost sure to follow. However, if the fetus's body delivers first and the head is a little bit bigger than the body, the head may be trapped within a pelvis that is too small or by a cervix that is only partially dilated. This is one of the most feared complications in all of obstetrics practice and it is not always predictable. If it happens, death or brain damage is likely to occur despite the presence of the most skilled obstetrician.

For these reasons, few women today choose vaginal breech delivery. In special circumstances, vaginal breech delivery may be attempted in relative safety. These situations are described in more detail in another section. In most cases, however, babies in breech presentation undergo cesarean section to avoid these complications.

Less commonly, the fetus presents crosswise with its back or chest nearest to the mother's birth canal. Obstetricians call this a transverse lie. It is impossible for a fetus presenting as transverse lie to safely deliver vaginally. Thus, babies found to be in transverse lie position at the time of delivery are always delivered by cesarean section.

Exceptions to delivering a malpresented baby by cesarean section are cases where the fetus may be repositioned with use of a procedure called external cephalic version. Usually this cannot be done once labor has begun. At times, this can be a useful procedure; it is discussed in more detail in another section.

Other Reasons for Cesarean Section

There are a variety of less common reasons why a woman may undergo cesarean delivery. These include cases of placenta previa, a condition in which the placenta is implanted over the opening of the cervix and the fetus cannot exit without causing massive bleeding. Another indication is placental abruption. This occurs when the placenta separates before the fetus is born, thus exposing the fetus to the dangers of lack of oxygen.

The most common single indication for cesarean delivery is repeat cesarean. In the past, it was felt that women who had had a cesarean section could not safely deliver vaginally in subsequent pregnancies. The saying ?once a cesarean, always a cesarean? was accepted in obstetrics for the better part of the century. In the 1970s and 1980s, doctors discovered that this was not the case-today, many women have successful vaginal deliveries after having one or more cesareans. Although the risks of uterine rupture are quite small, the outcome can occasionally be catastrophic, resulting in death or brain damage of the fetus and possibly the need for hysterectomy in the mother. Scientists have weighed the risks of an occasional extremely bad outcome associated with an attempted vaginal birth after cesarean against the maternal risks associated with unnecessary repeat cesareans and there is no clear winner. For this reason, women today are allowed to weigh the risks and make their own choice between attempting labor/vaginal delivery and repeating a cesarean section. These decisions are not easy to make and are worthy of extended discussions with your doctor and partner or support person(s).