DEAR MAYO CLINIC: My daughter was born via cesarean section two years ago. I am pregnant again and would like a VBAC (vaginal birth after cesarean). Would a VBAC be safe for me and my baby given that I had a placental abruption during my second pregnancy? What other risks are there with a VBAC?

ANSWER: In many cases, having a VBAC is a safe option for both mother and baby. But there are a variety of considerations -- including your history of placental abruption -- that you should discuss with your obstetrician before you make a decision about attempting a VBAC.

The term "VBAC" often is used to refer to the decision to try to have a vaginal birth after a cesarean section, or C-section. The decision you and your doctor need to make is whether you will allow your body to go into labor -- either spontaneous or induced labor -- instead of having a scheduled C-section. This process is called a trial of labor after cesarean, or TOLAC.

TOLAC can lead to a vaginal birth. But it could end in a C-section, too. Up to 75 percent of women who attempt a VBAC deliver their babies through a vaginal birth. The likelihood of a successful VBAC depends on many factors.

The main risk of attempting a VBAC is uterine rupture or disruption of the scar from a previous C-section incision. The risk of uterine rupture after one C-section is about 1 percent. Up to 10 percent of uterine ruptures result in brain injury to the baby or, although rare, death of the baby. The overall risk of serious injury is about 1 in 1,000.

But there are benefits to having a VBAC, too. For mothers those benefits include shorter hospital stays, fewer complications after delivery and quicker recovery. In addition, you avoid the risk of complications that come with multiple C-sections.

In general, women who have had only one or two C-sections are good candidates to attempt a VBAC. The incisions for the prior C-sections should be low transverse uterine incisions that were closed in two layers. This information can be confirmed from your previous operative report. The previous C-section also needs to be more than 18 months from your current due date.

Women with the highest VBAC success rate are those who have already had a vaginal delivery; have labor that starts on its own at 40 weeks gestation or less; and whose cervix is dilated more than 3 centimeters when they arrive at the hospital. In addition, a successful VBAC is more likely if previous C-sections were done for reasons linked to the baby's health, rather than because labor did not progress.

Other factors that would raise your chance of having a successful VBAC include being younger than 35, Caucasian and at a healthy weight.

Your medical history also plays a role. VBAC is not recommended for women who have had a uterine rupture, extensive surgery for uterine fibroids or placenta previa. It is also not recommended if a baby is in the breech position or if you have had a previous classical or vertical uterine incision. Placental abruption -- a condition in which the placenta peels away from the inner wall of the uterus before delivery -- can be related to certain pregnancy risk factors, but it is often unpredictable. That makes it hard to tell if your history of placental abruption could affect your decision to pursue a VBAC.

To find out if a VBAC may be worth investigating further, talk to your obstetrician about your medical history and the risks and benefits of a VBAC in your situation. If you decide you'd like to attempt a VBAC, make sure you have easy access to a hospital that is well equipped to care for women who have VBACs. -- Staci Tanouye, M.D., Obstetrics and Gynecology, Mayo Clinic, Rochester, Minn.

(Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care. To submit a question, write to: medicaledge@mayo.edu. For health information, visit http://www.mayoclinic.com.)