Risk of Uterine Rupture in VBAC

Click here for the abstract of a newly published study which looks at one risk factor for uterine rupture in a subsequent VBAC attempt. It found that women who went into labor spontaneously and then had a C-section, as well as women who were induced but had a successful vaginal birth, had a lower rate of uterine ruptures in a subsequent VBAC.

Women with a history of either spontaneous labor or vaginal birth had one uterine rupture for every 460 deliveries [rate of 2.17/1000]; women without this history who required induction or augmentation to proceed with a VBAC attempt had one uterine rupture for every 95 deliveries [10.52/1000].

Unfortunately, I don’t have access to the full study, but this sentence makes me wonder — were the women in the first group induced or augmented at all? We know that there is a difference in the rate of uterine rupture in labors that are not induced, compared with those that are; and also that there is a difference in uterine rupture rates depending on type of induction:

Uterine rupture occurred at a rate of 1.6 per 1000 among women with repeated cesarean delivery without labor (11 women), 5.2 per 1000 among women with spontaneous onset of labor (56 women), 7.7 per 1000 among women whose labor was induced without prostaglandins (15 women), and 24.5 per 1000 among women with prostaglandin-induced labor (9 women).

Did the researchers in the first-mentioned study differentiate between labors that were induced and those that were not? or between types of induction? I would like to know what was the rate of uterine rupture in women with a prior spontaneous onset of labor or successful vaginal birth both with and without induction or augmentation; as well as the rate of uterine rupture both with and without induction/augmentation in the second group of women as well. It made a difference in the second study, so I would expect to see something similar in the first study…although it is possible that women in the second study who were induced were less likely to have had a previous successful birth or spontaneous onset of labor. I would also like to know if these ruptures were dehiscence or full ruptures, because that makes a difference in perinatal mortality and maternal morbidity. I assume that the term “rupture” includes both complete and incomplete ruptures, and in one large study I’ve blogged about before, there were greater or equal instances of incomplete uterine rupture ( which “was associated with minimal maternal and perinatal morbidity”) than there were of complete uterine ruptures, depending on whether or not the woman labored.

Also, women with previous vaginal births were more likely to have successful VBACs; and,

The rate of uterine rupture decreased after the first successful VBAC and did not increase thereafter: 0.87%, 0.45%, 0.38%, 0.54%, 0.52% (P=.03). The risk of uterine dehiscence and other peripartum complications also declined statistically after the first successful VBAC. No increase in neonatal morbidities was seen with increasing VBAC number thereafter.

So there are a lot of factors that go into the likelihood of uterine rupture in a VBAC attempt. While certainly not risk-free, if you’ve had a successful vaginal birth — either before or after your C-section, or you’ve gone into labor on your own, or you plan on declining induction or augmentation in a future VBAC attempt, your risk of uterine rupture is very low.

Still, “the best defense is a good offense” — the best way to avoid the hassle of the whole VBAC issue is to avoid a C-section in the first place. While that’s not always possible, and there are good reasons for a C-section in certain instances, far too many C-sections take place because of failed inductions — inductions which were not medically indicated, and which we now know raise the rate of future uterine rupture if you want to try to have a VBAC. So, if you’re thinking that you’re tired of being pregnant, and you just don’t want to wait any more, or the doctor is saying that you’re past 40 weeks, so you need to be induced, or some other reason that is not a valid medical reason, you just might want to think again.


One Response

  1. Amen to that. Every time I hear a friend who is about to be induced and act as if it’s a completely normal thing makes me cringe.

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