Inducing labor and VBAC

When labor does not start on its own and delivery needs to happen soon, contractions can be artificially started (induced) with medicine. But this is not always safe when a woman has a cesarean scar on her uterus. In rare cases, the scar breaks open during vaginal birth after cesarean (VBAC). This is called uterine rupture.

What medicines are used to start labor?

Misoprostol (Cytotec) is used in many hospitals to soften the cervix, making it more likely to flatten and thin. Intravenous oxytocin (Pitocin) is sometimes used to start or strengthen (augment) contractions.

• Misoprostol. Starting labor (induction) with misoprostol is not recommended for use in VBAC.¹
• Oxytocin. Some doctors avoid the use of any medicine to start a VBAC trial of labor. Other doctors are comfortable with the careful use of oxytocin to start labor when the cervix is soft and opening (dilating).

Aiding a slow labor (augmentation) with careful use of oxytocin has rarely been linked to uterine rupture.²

How often does uterine rupture happen?

In one large study, uterine rupture occurred in:³

• About 25 out of 1,000 women who were induced with misoprostol.
• About 8 out of 1,000 women who were induced with oxytocin.
• About 5 out of 1,000 women who had a spontaneous labor.
• About 12 out of 1,000 women who had a planned repeat cesarean without labor.

When is inducing a VBAC a possibility?

• Inducing a VBAC labor is not safe when labor has not started on its own and the cervix is closed and firm. This is especially true if you have never had a vaginal delivery. In this case, starting labor with misoprostol (Cytotec) or oxytocin (Pitocin) raises the risk of uterine rupture.
• Some doctors will place a small tube with a balloon into the cervix to soften and open it. This is a safer way to carefully use oxytocin, with little or no increase in the risk of uterine rupture.
• When a VBAC labor has not started on its own but the cervix is soft and opening, oxytocin may be carefully used to help start labor. Oxytocin may also be used sparingly to get a slow labor going again. This medicine is less likely than misoprostol to increase your uterine rupture risk.^{4, 3}

If your labor stalls and the sparing use of oxytocin does not appear to be helping, a cesarean may be needed. This is true for any woman in labor for a vaginal delivery.

Author:	Kathe Gallagher, MSW	Last Updated: April 20, 2007
Medical Review:	Joy Melnikow, MD, MPH - Family Medicine Kirtly Jones, MD - Obstetrics and Gynecology
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