Part 1 reviewed the current state of cesarean sections in the US. It also reviewed ACOG recommendations for management of abnormal first and second stage of labor. Part 2 will discuss the second most common indication for primary c/s, an abnormal fetal heart rate tracing, as well as the effects of induction on c/s rate, and other common indications for primary c/s, such as twin and breech presentation. Part 3 will discuss what the patient can expect from their provider based on these recommendations.
ACOG Obstetric Care Consensus: Safe Prevention of the Primary Cesarean Delivery (2014)
Abnormal Fetal Heart Rate Tracings
Interpreting Continuous Fetal Monitoring
An abnormal (or indeterminate) fetal heart rate is the second most common reason for performing a primary c-section. Fetal heart rate tracings are divided into 3 categories. Category 1 tracings are normal. Category 1 patterns are a reliable indicator that the fetal cord blood pH is normal, and no intervention is required.
Category 3 tracings are definitely abnormal and require immediate intervention. They are associated with fetal acidosis, encephalopathy, and cerebral anemia. Interventions include changing maternal position, supplementing with oxygen, checking for maternal hypotension or tachysystole, and checking for other causes, like abruption or umbilical cord prolapse. These interventions should be attempted quickly, and if the Category 3 tracing does not resolve, then delivery is indicated as promptly and as safely as possible. These are rare tracings.
Most fetal heart tracings fall into Category 2; they are indeterminate. This is a catch-all category for the tracings that are not either totally normal, or totally abnormal. There are a variety of tracings that fall into this category, some that may indicate a nonreassuring fetal heart rate and many that do not. Tracings more likely to, “indicate fetal acidemia, such as minimal variability or recurrent late decelerations, should be approached with in utero resuscitation. They, “require evaluation, continued surveillance, initiation of appropriate corrective measures when indicated, and re-evaluation.” Because most c-sections are done for Category 2 tracings, it is important to attempt to resolve the indeterminate tracing and to evaluate fetal well being before determining fetal status is nonreassuring and moving toward delivery.
Determining Fetal Status with a Category 2 Tracing
Fetal heart rate accelerations are associated with a normal umbilical cord blood pH. Scalp stimulation can be used to elicit an acceleration to reassure the provider that the fetus is not acidotic.
Recurrent variable decelerations are believed to be a physiological response to umbilical cord compression and are not necessarily pathologic. However, over time they can result in fetal acidemia if recurrent and persistent. Starting an amnioinfusion has been shown to reduce variable decelerations and to decrease c-section rates.
Prolonged decelerations lasting between 2 and 10 minutes can indicate rapid cervical change, maternal hypotension, placental abruption, umbilical cord prolapse, or uterine rupture.
Uterine tachysystole is defined as more than 5 contractions in 10 minutes, averaged over 30 minutes. This can stress the fetus and result in heart rate changes, including prolonged and late decelerations. Tachysystole is more likely to occur because of medications, such as cytotec or pitocin, that stimulate the uterus. However, it can also occur spontaneously. Discontinuing the medication and using a uterine relaxant can decrease contractions and improve the fetal heart rate.
Effect of Induction on C-section Rates
Induced labors have increased from 9.5% of births in 1990 to 23.1% of births in 2008. It has been assumed that since women who undergo induction are more likely to have a c-section, that induction itself is a risk factor for c-section. However, “this assumption is predicated on a faulty comparison of women who are induced versus women in spontaneous labor. Studies that compare induction of labor to its actual alternative, expectant management awaiting spontaneous labor, have found either no difference or a decreased risk of cesarean delivery among women who are induced.” There are increased risks of stillbirth, neonatal death, and infant death at gestations of 41 0/7 wks and beyond. Induction of labor after this point is associated with a decreased risk of cesarean and decreased risk of perinatal morbidity and mortality. Prior to 41 0/7 weeks, induction should be reserved for maternal and fetal medical conditions.
Variations in managing labor induction, however, can increase or decrease cesarean rates. Many studies have found that the use of a cervical ripener on an unfavorable cervix lead to lower c-section rates. Redefining the latent phase before calling a failed induction will also decrease c-section rates. Studies show that the latent phase is longer in an induced labor; being patient while maternal and fetal status are stable is reasonable. Membrane rupture and pitocin administration should be continued for AT LEAST 24 hours before declaring a failed induction.
Other Common Reasons for Cesarean Delivery
Fetal Malpresentation
3.7% of pregnancies at 37 weeks are breech presentation; 85% of these pregnancies are delivered by c-section. External cephalic version done at 36 weeks should be offered by the obstetrician whenever possible. Version is more likely to be successful when planned and performed under regional anesthesia. If vaginal breech delivery is intended, informed consent for the woman should include that there is a higher risk of perinatal and neonatal mortality than with a planned c-section.
Suspected Fetal Macrosomia
“SUSPECTED FETAL MACROSOMIA IS NOT AN INDICATION FOR DELIVERY AND RARELY IS AN INDICATION FOR CESAREAN DELIVERY.” [my emphasis] Cesarean section should be reserved for estimated fetal weights of over 5,000g in women without diabetes and over 4,500g in women with diabetes. Patients should be informed that ultrasounds estimating fetal weight, especially in the 3rd trimester, are not as accurate. “Ultrasonography for estimated fetal weight in the third trimester should be used sparingly and with clear indications.”
Excessive Maternal Weight Gain
Women who gain more than the recommended amount of weight are at increased risk of cesarean delivery. Women should be counseled on recommended weight gain.
Twin Gestation
The rate of cesarean sections in women with twins has increased from 53% to 75% from 1995 to 2008, and even in twins where twin A was vertex, cesareans increased from 45% to 68%. “PERINATAL OUTCOMES FOR TWIN GESTATIONS IN WHICH THE FIRST TWIN IS CEPHALIC PRESENTATION ARE NOT IMPROVED BY CESAREAN DELIVERY.” [my emphasis]. Women should be counseled to attempt vaginal delivery if the first twin is vertex.
Herpes Simplex Virus
Women with a history of genital herpes should be given acyclovir for viral suppression within 3-4 weeks of expected delivery, even if there was no outbreak in the current pregnancy. Cesarean delivery is recommended in women with an active outbreak at time of delivery. It is not recommended in women with a history of genital herpes but no active outbreak during labor.
Continuous Labor Support
“One of the most effective tools to improve labor and delivery outcomes is the continuous presence of support personnel, such as a doula… The presence of continuous one-on-one support during labor and delivery was associated with improved patient satisfaction and a statistically significant reduction in the rate of cesarean delivery”.
Part 1 reviewed the current state of cesarean sections in the US. It also reviewed ACOG recommendations for management of abnormal first and second stage of labor. Part 2 discussed the second most common indication for primary c/s, an abnormal fetal heart rate tracing, as well as the effects of induction on c/s rate, and other common indications for primary c/s, such as twin and breech presentation. Part 3 will discuss what the patient can expect from their provider based on these recommendations.