While strongly supporting the concept of vaginal birth after previous cesarean (VBAC) delivery, the American College of Obstetricians and Gynecologists (ACOG) has issued an updated practice pattern that recommends a more cautious approach and consideration of individual risk factors before attempting a trial of labor. The report discusses the background of VBAC, clinical considerations and recommendations, selection of candidates for a trial of labor, risks and benefits, contraindications for VBAC, management of labor in patients undergoing VBAC and counseling patients. An algorithm for determining the feasibility of VBAC in a patient is also included in the ACOG report. ACOG Practice Pattern No. 2 was published in the October 1998 issue of Obstetrics and Gynecology.

According to ACOG, improvements in obstetric care over the years have made a trial of labor relatively safe for both mother and infant. However, VBAC has been associated with a risk of uterine rupture, and other maternal and infant complications have been associated with an unsuccessful trial of labor. The occurrence of uterine rupture appears to be associated with the type and location of the previous incision. ACOG states that of the four types of incisions for cesarean delivery (classical, T-incision, low vertical and low transverse), low-transverse scars are least likely to rupture.

ACOG emphasizes that it is ultimately up to the physician and patient to decide whether to attempt VBAC, and ACOG strongly objects to any mandate by a third party for a trial of labor after previous cesarean delivery. The following are the criteria that ACOG lists for selecting a candidate for VBAC:

• One or two prior low-transverse cesarean deliveries.

• Clinically adequate pelvis.

• No other uterine scars or previous rupture.

• Physician readily available throughout labor capable of monitoring labor and performing an emergency cesarean delivery.

• Availability of anesthesia and personnel for emergency cesarean delivery.

VBAC should not be undertaken in women who have had a prior classic or T-shaped incision or who have had other transfundal uterine surgery. Other contraindications for VBAC are a contracted pelvis, medical or obstetric complication that precludes vaginal delivery, and an inability to perform immediate emergency cesarean delivery. ACOG also notes that a combination of factors, which by themselves may not be compelling for cesarean delivery, may influence a decision to forego VBAC.

The following recommendations from ACOG, based on consistent scientific evidence, have been excerpted from the practice pattern:

• 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.

• A previous uterine incision extending into the fundus is a contraindication.

These following recommendations are, according to ACOG, based on limited or inconsistent scientific evidence:

• Women with two previous low-transverse cesarean deliveries and no contraindications who wish to attempt VBAC may be allowed a trial of labor. They should be advised that the risk of uterine rupture increases as the number of cesarean deliveries increases.

• Use of oxytocin or prostaglandin gel for VBAC requires close patient monitoring.

• Women with a vertical incision within the lower uterine segment that does not extend into the fundus are candidates for VBAC.

These following recommendations are based on consensus and expert opinion:

• VBAC should only be attempted in institutions equipped to respond to emergencies with physicians readily available to provide emergency care.

• After thorough counseling that weighs the individual benefits and risks of VBAC, the ultimate decision to attempt this procudure or undergo a repeat cesarean delivery should be made by the patient and her physician.

To order copies of the practice pattern or obtain further information, call ACOG at 800-762-2264, ext. 784.