Dear Henci,

Can you tell me if there is any research on how long a scar actually needs to heal? Some say VBAC is okay after 18 months, some say 24, some say longer.

If an athlete seriously injures - let's say - his knee, he will drop out for a few weeks or maybe a few months before he once again subjects his injured (and surgically corrected) knee to extreme continuing strain.

The uterus on the other hand has 9 months to slowly prepare for one short period of increased stress.

So why is it safe for an athlete to "jump around" after a few weeks but not for a woman to attempt VBAC if pregnant after the same time?

When is the healing process actually completed? At which point will it just not get any better? And is there any connection between uterine rupture and time?

Thank you for your help!

Here is what we know: five studies comparing rates of the scar giving way during VBAC labors with shorter versus longer intervals between deliveries have found increased rates with the shorter interval (Bujold 2002; Huang 2002; Landon 2006; Shipp 2001; Stamilio 2007). Rates at the shorter interval ranged from 1% to 3%, or, if you prefer, 97% to 99% odds of the scar being just fine, but this is difficult to interpret meaningfully because the studies used different intervals, and some studies used interpregnancy interval while others used interdelivery interval. (Interpregnancy and interdelivery rates are not transposable because pregnancy duration may be cut short by preterm delivery.) However, no study reported a scar rupture rate with the shorter interval of more than 3%, that number coming from a study in which the shorter interval was an interdelivery interval of 24 months or less compared with greater than 24 months (Bujold 2002). Moreover, this rate is almost certainly substantially higher than it could be with optimal care because a very large study reporting a rate of  only 1% used the same interdelivery interval (Landon 2006). The take-home message here is that it's a good idea to wait 15 months before trying to conceive again, but if an unplanned pregnancy occurs sooner, it doesn't mean the woman is at extraordinarily high risk for scar rupture.

-- Henci

Bujold E, Mehta SH, Bujold C, et al. Interdelivery interval and uterine rupture. Am J Obstet Gynecol 2002;187(5):1199-202.

Huang WH, Nakashima DK, Rumney PJ, et al. Interdelivery interval and the success of vaginal birth after cesarean delivery. Obstet Gynecol 2002;99(1):41-4.

Landon MB, Spong CY, Thom E, et al. Risk of uterine rupture with a trial of labor in women with multiple and single prior cesarean delivery. Obstet Gynecol 2006;108(1):12-20.

Shipp TD, Zelop CM, Repke JT, et al. Interdelivery interval and risk of symptomatic uterine rupture. Obstet Gynecol 2001;97(2):175-7.

Stamilio DM, DeFranco E, Pare E, et al. Short interpregnancy interval: risk of uterine rupture and complications of vaginal birth after cesarean delivery. Obstet Gynecol 2007;110(5):1075-82.