Cesarean Section

Definition

A cesarean section (also referred to as c-section) is the birth of a fetus accomplished by performing a surgical incision through the maternal abdomen and uterus. It is one of the oldest surgical procedures known throughout history.

Purpose

Although Healthy People 2010 established a goal of a 15 percent rate for c-sections in the United States, the ideal rate has not been established. As of 2004, the average c-section rate is one out of every four births or approximately 26 percent of all births. A c-section allows safe and quick delivery of a baby when a vaginal delivery is not possible. The surgery is performed in the presence of a variety of maternal and fetal conditions with the most commonly accepted indications being complete placenta previa, cephalopelvic disproportion (CPD), placental abruption, active genital herpes, umbilical cord prolapse, failure to progress in labor or dystocia, proven nonreassuring fetal status, and benign and malignant tumors that obstruct the birth canal. Indications that are more controversial include breech presentation, previous c-section, major congenital anomalies, cervical cerclage, and severe Rh isoimmunization. C-sections have a higher maternal mortality rate than vaginal births with approximately 5.8 women per 100,000 live births dying, and half of these deaths are ascribed to the operation and a coexisting medical condition. Perinatal morbidity is associated with infections, reactions to anesthesia agents, blood clots, and bleeding.

Description

According to the United States Public Health Service, 35 percent of all c-sections are performed because the woman has had a previous c-section. The skin incision for a c-section is either transverse (Pfannenstiel) or vertical and does not indicate the type of incision made into the uterus. "Once a cesarean, always a cesarean," is a rule that originated with the classical, vertical uterine incision. It was believed that the resulting scar weakened the uterus wall and was at risk of rupture in subsequent deliveries. As of 2004, the incision is almost always made horizontally across the lower uterine segment, called a low transverse incision. This results in reduced blood loss and a decreased chance of rupture. This kind of incision allows many women to have a vaginal birth after a cesarean (VBAC).

Failure to progress and/or dystocia is the second most common reason for a c-section and represents about 30 percent of all cases. Uterine contractions may be weak or irregular, the cervix may not be dilating, or the mother's pelvic structure may not allow adequate passage for birth. When the baby's head is too large to fit through the pelvis, the condition is called cephalopelvic disproportion (CPD). Failure to progress, however, can only be diagnosed with documentation of adequate contraction strength. The force of the contractions can be measured with an intrauterine pressure catheter (IUPC), which is a catheter that can be placed through the cervix into the uterus to measure uterine pressure during labor. Calculation of this force is determined by subtracting the baseline (resting) pressure from the peak pressure recorded for all contractions in a ten-minute period. This pressure calculation results in a force termed Montevideo units. A minimum of 200 Montevideo units are required before the forces of labor can be considered adequate. If the Montevideo units are less than this ten-minute sum and the fetal heart rate is reassuring, augmentation of labor with pitocin may be necessary.

Breech presentation occurs in about 3 percent of all births, and approximately 12 percent of c-sections are performed to deliver a baby in a breech presentation: buttocks or feet first. Breech presentations were still delivered vaginally in the 1970s, but with the advent of the malpractice climate, many doctors shied away from this practice, opting to perform a c-section. As a result, physicians who were being trained during that time period never learned how to manage a breech vaginal delivery. There was some change in this approach in the 1990s, and doctors are once again learning how to manage this situation; however, it is still uncertain whether this knowledge will be used in their practice.

Fetal distress or the more appropriate term, nonreassuring fetal heart rate, accounts for almost 9 percent of c-sections. With the introduction of electronic fetal monitoring (EFM) in the 1970s, doctors had more information for assessing fetal well-being. It was assumed that fetal monitoring would transmit signals of distress, thus, the EFM tracing became a legal document. There is still considerable debate as to what a non-reassuring FHR really is, but there are other parameters available to assist in this interpretation. When a fetus experiences stress, (oxygen deprivation) in utero, it may pass meconium (feces) into the amniotic fluid. The appearance of meconium in the fluid along with a questionable EFM tracing may indicate that a fetus is becoming compromised. At this point, if a woman is in early labor, a c-section may have to be performed. If, however, she is close to delivery, a vaginal delivery is often quicker. Oxygen deprivation may also be determined by testing the pH of a blood sample taken from the baby's scalp: a pH of 7.25-7.35 is normal; between 7.2 and 7.25 is suspicious; and below 7.2 is a sign of trouble. If the sample is equivocal, it can be repeated every 20 to 30 minutes.

The remaining 14 percent of c-sections occur secondary to other emergency situations, including the following:

• Umbilical cord prolapse: This situation occurs when the cord is the presenting part from the vagina. It becomes compressed and cuts off blood flow to the baby. The birth attendant must insert a hand into the vagina and relieve pressure on the cord until a c-section is performed.
• Placental abruption: The placenta separates from the uterine wall before the baby is born. If it is a complete abruption, the baby's blood flow will be cut off completely. The mother experiences severe pain, possible bleeding, and her abdomen feels rock hard. This situation demands an immediate c-section. Partial abruptions can occur without endangering the mother or the baby, but they need to be closely monitored. The risk of placental abruption is higher in multiple births and in women with high blood pressure.
• Placenta previa: With a complete previa, the placenta covers the cervix completely, and the mother may experience painless bleeding. With a complete previa, a c-section is mandatory as cervical dilation would cause bleeding. The baby is often in a transverse position in this case, which means it is lying horizontally across the pelvis. Women with partial previas will usually need a c-section due to bleeding problems, but those with marginal previas can often deliver vaginally.
• Active genital herpes: Any active herpetic lesions in the vaginal area can infect the baby as it passes through the birth canal. This is especially true for those with a primary outbreak, a first-time exposure.
• Mother's health status: A c-section may be necessary in women with pre-existing diseases, such as diabetes, hypertension, pregnancy induced hypertension (preeclampsia), autoimmune diseases such as lupus erythematosus, and blood incompatibilities. Each case must be evaluated on an individual basis in these instances to achieve the optimal outcome for baby and mother.

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Author Info: Linda K. Bennington RNC, MSN, CNS, Thomson Gale, Gale, Detroit, Gale Encyclopedia of Children's Health, 2006

This feature is for informational purposes only and should not be used to replace the care and information received from your healthcare provider. Please consult a healthcare professional with any health concerns you may have.