Practice Guidelines
ACOG Releases Guidelines for Vaginal Birth After Cesarean Delivery
The American College of Obstetricians and Gynecologists (ACOG) recently issued clinical management guidelines for vaginal birth after cesarean delivery (VBAC) in various situations. The complete guideline, ACOG Practice Bulletin no. 54, appeared in the July 2004 issue of Obstetrics and Gynecology.
According to the report, the cesarean delivery rate in the United States increased from 5 percent to nearly 25 percent between 1970 and 1988. The authors attribute this increase to pressure on physicians to not perform vaginal breech deliveries and midpelvic forceps deliveries, and an increasing reliance on continuous electronic monitoring of fetal heart rate and uterine contraction patterns. Several large series found that a trial of labor after a previous cesarean delivery was relatively safe, prompting organizations such as the National Institutes of Health and the ACOG to endorse VBAC as a way to reduce the number of cesarean deliveries in the United States. Between 1989 and 1996, the cesarean delivery rate decreased as the VBAC rate increased. However, reports of uterine rupture and other complications during trials of labor after previous cesarean deliveries caused this trend to reverse.
No randomized trials have compared maternal or neonatal outcomes for repeat cesarean delivery and VBAC. Rather, VBAC recommendations have been based on data from large clinical studies suggesting that the benefits of VBAC outweigh the risks in most women with a previous low-transverse cesarean delivery. Most of these trials have been performed in university or tertiary-level centers with in-house obstetric and anesthesia coverage. ACOG notes that only a few studies have documented the relative safety of VBAC in smaller community hospitals or facilities where resources may be more limited. The report adds that women who fail a trial of labor are at risk for several maternal complications, including uterine rupture, the need for transfusion, hysterectomy, endometritis, and perinatal morbidity and mortality.
Clinical Considerations and Recommendations
According to the report, the evidence suggests that most patients who have had a low-transverse uterine incision from a previous cesarean delivery and who have no contraindications for vaginal birth are candidates for a trial of labor. Criteria for selecting candidates for VBAC include the following: (1) one previous low-transverse cesarean delivery; (2) clinically adequate pelvis; (3) no other uterine scars or previous rupture; (4) a physician immediately available throughout active labor who is capable of monitoring labor and performing an emergency cesarean delivery; and (5) the availability of anesthesia and personnel for emergency cesarean delivery.
The report also discusses other specific obstetric circumstances where a trial of labor may be offered. According to the report, for women who have had two previous low-transverse cesarean deliveries, only those with a previous vaginal delivery should be considered candidates for a spontaneous trial of labor. They state that 60 to 90 percent of women attempting a trial of labor who give birth to infants with macrosomia are successful, and the rate of uterine rupture appears to be increased only in women who have not had a previous vaginal delivery. Awaiting spontaneous labor beyond 40 weeks of gestation decreases the likelihood of successful VBAC but does not increase the risk of uterine rupture. According to one case series and four retrospective studies, women who have had a previous low-vertical uterine incision were just as likely to have successful VBAC as women who have had a previous low-transverse uterine incision. Two trials showed no significant difference between rates of successful VBAC and uterine rupture between women with twin or singleton gestations.
Success rates for trials of labor
Most published series of women attempting a trial of labor after a previous cesarean delivery demonstrate that 60 to 80 percent have successful vaginal births. ACOG reports that for an individual patient, there is no completely reliable way to predict the success of a trial of labor. Success rates are similar for women whose first cesarean delivery was performed for a nonrecurring indication and for women who have not undergone a previous cesarean delivery. Although most women who have undergone a cesarean delivery because of dystocia can have a successful VBAC, the percentage may be lower (50 to 80 percent) than for those with nonrecurring indications (75 to 80 percent). Women who have given birth vaginally at least once are nine to 28 times more likely to have a successful trial of labor than women who have not given birth vaginally. The likelihood of failure of a trial of labor is reduced by 30 to 90 percent if the most recent delivery was a successful VBAC. The likelihood of successful VBAC is impacted negatively by labor augmentation and induction, maternal obesity, gestational age beyond 40 weeks, interdelivery interval of less than 19 months, and birth weight greater than 4,000 g (8 lb, 11 oz).
Risks and benefits associated with VBAC
Repeat cesarean delivery and VBAC both have risks. Successful VBAC generally is associated with shorter maternal hospitalizations, fewer infections, less blood loss and fewer transfusions, and fewer thromboembolic events than cesarean delivery. However, a failed trial of labor may be associated with major maternal complications, such as hysterectomy, uterine rupture, operative injury, increased maternal infection, need for transfusion, and neonatal morbidity. Multiple cesarean deliveries are associated with an increased risk of placenta previa and accreta.
With VBAC, the incidence of maternal death is extremely low. The incidence of perinatal death is less than 1 percent, and is more likely to occur during a trial of labor than an elective repeat cesarean delivery.
Uterine rupture during a trial of labor after a previous cesarean delivery is a life-threatening complication directly associated with attempted VBAC. The patient's obstetric history influences the risk of uterine rupture. A previous vaginal birth significantly reduces the risk of uterine rupture. Also, the longer the length of time between deliveries, the lower the risk of rupture. Women who attempt VBAC who have interdelivery intervals of less than 24 months have a two- to three-fold increased risk of uterine rupture compared with women whose interdelivery interval is more than 24 months.
Induction or augmentation of labor
A successful VBAC is more likely to result from spontaneous labor than labor induction or augmentation. The report states that evidence shows that cervical ripening with prostaglandin preparations increases the likelihood of uterine rupture. Misoprostol also has been associated with a high rate of uterine rupture in women with a previous cesarean delivery. The report recommends not using prostaglandins for induction of labor in most women with a previous cesarean delivery.
Midtrimester delivery
The decision to attempt a trial of labor in the midtrimester in women with a previous cesarean delivery should be based on the patient's individual circumstances, including the number of previous cesarean deliveries, placentation, gestational age, and the woman's desire to preserve reproductive function.
Summary of Recommendations
The following recommendations are based on good and consistent scientific evidence (Strength of Recommendation Taxonomy [SORT] = A; see page 1201 for an explanation of SORT):
• Most women with one previous cesarean delivery with a low-transverse incision are candidates for VBAC and should be counseled about VBAC and offered a trial of labor.
• Epidural anesthesia may be used for VBAC.
The following recommendations are based on limited or inconsistent scientific evidence (SORT = B):
• Women with a vertical incision within the lower uterine segment that does not extend into the fundus are candidates for VBAC.
• The use of prostaglandins for cervical ripening or induction of labor in most women with a previous cesarean delivery should be discouraged.
The following recommendations are based primarily on consensus and expert opinion (SORT = C):
• Because uterine rupture may be catastrophic, VBAC should be attempted in institutions equipped to respond to emergencies with physicians immediately available to provide emergency care.
• After thorough counseling that weighs the individual benefits and risks of VBAC, the ultimate decision to attempt this procedure or undergo a repeat cesarean delivery should be made by the patient and her physician. This discussion should be documented in the medical record.
• Vaginal birth after a previous cesarean delivery is contraindicated in women with a previous classical uterine incision or extensive transfundal uterine surgery.
Practice Guideline Briefs
Influenza Activity in the United States
The Centers for Disease Control and Prevention (CDC) has updated its annual report on influenza activity in the United States. "Update: Influenza Activity-United States and Worldwide, 2003-04 Season, and Composition of the 2004-05 Influenza Vaccine" is available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5325a1.htm.
During last year's influenza season in the United States, influenza A accounted for 99 percent of all influenza infections. The remaining 1 percent consisted of influenza B. Among the influenza A viruses, 99.9 percent were H3N2 viruses, and 0.1 percent were H1 viruses.
As measured by the 122 Cities Mortality Reporting System, the percentage of deaths in the United States attributed to pneumonia and influenza (P&I) exceeded the epidemic threshold during nine consecutive weeks. The percentage of P&I mortality reached a peak of 10.3 percent during the weeks ending January 10 and 17, 2004. During the previous four influenza seasons, the peak percentage of P&I mortality ranged from 8.1 to 11.2 percent.
As of May 31, 2004, 152 influenza-associated deaths in U.S. residents younger than 18 years were reported to the CDC by 40 states. All patients had influenza virus infection detected by rapid antigen testing, viral culture, or other laboratory methods.
• Avian Influenza. In December 2003, one confirmed case of avian influenza A (H9N2) virus infection was reported in a child in Hong Kong. The child had fever, cough, and nasal discharge in late November, was hospitalized for two days, and fully recovered. The source of this child's H9N2 infection is unknown.
Between January and March 2004, 34 confirmed human cases of avian influenza A (H5N1) virus infection were reported in Vietnam and Thailand. The cases were associated with severe respiratory illness requiring hospitalization and a case-fatality proportion of 68 percent (Vietnam: 22 cases, 15 deaths; Thailand: 12 cases, eight deaths). A substantial proportion of the cases were children and young adults. These cases were associated with widespread outbreaks of highly pathogenic H5N1 influenza among domestic poultry.
In March 2004, health authorities in Canada reported two confirmed cases of avian influenza A (H7N3) virus infection in poultry workers who were involved in culling of poultry during outbreaks of highly pathogenic H7N3 on farms in the Fraser River Valley, British Columbia. One patient had unilateral conjunctivitis and nasal discharge, and the other had unilateral conjunctivitis and headache. Both illnesses resolved without hospitalization.
During the 2003-2004 influenza season, a case of avian influenza A (H7N2) virus infection was detected in an adult male from New York, who was hospitalized for upper and lower respiratory tract illness in November 2003. Influenza A (H7N2) virus was isolated from a respiratory specimen from the patient, whose acute symptoms resolved. The source of this person's infection is unknown.
• Composition of the Influenza Vaccine for the 2004-2005 Season. The Food and Drug Administration's Vaccines and Related Biological Products Advisory Committee (VRBPAC) recommended that the 2004-2005 trivalent influenza vaccine for the United States contain A/New Caledonia/20/99-like (H1N1), A/Fujian/411/2002-like (H3N2), and B/Shanghai/361/2002-like viruses.
Because of the growth properties of the A/Wyoming/3/2003 and B/Jiangsu/10/2003 viruses, U.S. vaccine manufacturers are using these antigenically equivalent strains in the vaccine as the H3N2 and B components, respectively. The A/New Caledonia/20/99 virus will be retained as the H1N1 component of the vaccine.
• Influenza Vaccination Recommendations. Beginning with the 2004-2005 influenza season, the Advisory Committee on Immunization Practices (ACIP) recommends that all children six to 23 months of age and close contacts of children aged zero to 23 months receive annual influenza vaccination. The ACIP continues to recommend that all persons aged older than six months with certain chronic underlying medical conditions, their household contacts, and health care workers receive annual influenza vaccination.
AAP Report on Adolescent Sexuality
The Committee on Adolescence of the American Academy of Pediatrics (AAP) has released a new clinical report on adolescent sexual orientation advising physicians to be attentive to the needs of patients who may be confused over their sexual orientation or believe they are homosexual or bisexual. "Sexual Orientation and Adolescents" appears in the June 2004 issue of Pediatrics and is available online at http://pediatrics.aappublications.org/cgi/reprint/113/6/1827.
According to the report, adolescents frequently are asking physicians about sexual behavior and orientation. While physicians are not responsible for identifying homosexual or bisexual youth, physicians should create a clinical environment where adolescents feel safe to discuss sensitive personal issues, including sexuality and orientation.
The overall goal in caring for all youth is to promote normal adolescent development, social and emotional well-being, and physical health. One stark difference between homosexual and heterosexual youth is the suicide rate. According to the report, studies found homosexual youth were two to seven times more likely to attempt suicide than their heterosexual peers. They also are two to four times more likely to be threatened with a weapon at school, and are more likely to engage in the use of drugs and alcohol.
The report urges physicians to offer a safe and supportive environment to all youth. Among the recommendations are the following:
• Assure patients that their confidentiality is protected.
• Be aware of the special issues surrounding the development of sexual orientation.
• Use gender-neutral language in discussing sexuality (i.e., use of the word "partner" rather than "boyfriend" or "girlfriend," talk about "protection" rather than just "birth control").
• Encourage abstinence, discourage multiple partners, and discuss "safer sex" guidelines with all adolescents.
• Provide relevant information and resources about homosexual, bisexual, or heterosexual issues to patients who are concerned about these issues.
The authors of the report acknowledge that not all physicians may feel able to provide the type of care described in the report. Any physician who is unable to care for and counsel homosexual and bisexual youth should refer the patient to an appropriate colleague.
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