Need research on post date vbacs

[NinaD]

Hi mamas,

Can anyone point me towards some research showing the success of vbacs for post date babies. Also, I'd like to see the research that the OB's are looking at when they decide it's not worth the risk. I know that they're scared of lawsuits etc., but the fear must be coming from somewhere!

I posted another question earlier about post date vbacs. I'm nervous because I had a c-section after induction with my son at 16 days past EDD.

Thank you!!

[wombatclay]

The studies tend to show that VBAC success declines after 40 weeks... but it's not like the success rate falls like a rock or anything! It's a decline in success (and often an increase in the rate of various complications) but it's certainly possible to have a VBAC after 40 weeks. Also it's hard to say how much of the decline in success/increase in risk is due to medical management of a mama who is past her EDD (as defined by modern/western medicine) and how much is biological/physical.

The studies can be found by searching free databases like PubMed/Medline, and you'll find things like:

Coassolo KM, Stamilio DM, Pare E, Peipert JF, Stevens E, Nelson DB, et al. Safety and efficacy of vaginal birth after cesarean attempts at or beyond 40 weeks of gestation. Obstet Gynecol 2005;106:700–6.

Women past 40 weeks of gestation were more likely to have a failed VBAC. After controlling for confounders, the increased risk of a failed VBAC beyond 40 weeks remained significant (31.3% compared with 22.2%, odds ratio 1.36, 95% confidence interval 1.24-1.50). The risk of uterine rupture (1.1% compared with 1.0%) or overall morbidity (2.7% compared with 2.1%) was not significantly increased in the women attempting VBAC beyond the EDD.

and

Landon MB, Leindecker S, Spong CY, et al. The MFMU Cesarean Registry: factors affecting the success of trial of labor after previous cesarean delivery. Am J Obstet Gynecol. 2005;193(3 Pt 2):1016-1023.

Favorable intrapartum factors included greater cervical dilation at admission for delivery (OR, 2.6; 95% CI, 2.4-2.8, when dilated ≥4 cm), spontaneous labor without need for augmentation or induction (OR, 1.6; 95% CI, 1.5-1.8), and gestational age less than 41 weeks (OR, 1.6; 95% CI, 1.5-1.8)

and more general articles in industry publications like this:

Predicting the Likelihood of Successful Vaginal Birth After Cesarean Delivery
MARK H. EBELL, MD, MS, Athens Georgia
Am Fam Physician. 2007 Oct 15;76(8):1192-1194.

The review also identified factors that decreased the likelihood of vaginal birth (i.e., more than one previous cesarean delivery; induction of labor; birth weight greater than 4,000 g [8 lb, 13 oz]; and gestational age greater than 40 weeks).

This article takes info about gestational age from Guise J-M, McDonagh MS, Hashima J, Kraemer DF, Eden KB, Berlin M, et al. Vaginal birth after cesarean (VBAC) volume 1 and volume 2. Rockville, Md.: Agency for Healthcare Research and Quality, March 2003. AHRQ publication no. 03-E018. Accessed July 10, 2007, at: http://www.ncbi.nlm.nih.gov/books/bv...a.chapter.7149.

Anyway...that's the sort of thing that a "well read" OB should have seen. And basically they say yes, success declines. But not by much. The literature doesn't support vbac bans at some predetermined "cut off" gestation! And while some risks increase, the risk of UR doesn't increase significantly.

Good luck and happy birthing! I had two postdate hospital VBACS so I know it can happen!

[NinaD]

Thank you so much! I'll use your post as a starting point for my own research! Thanks for taking the time to put that together. I'm sure it took some time!

[ms sig]

wombatclay - What a thorough response. I was wondering the same thing. Thanks!

[smeep]

I also wonder if the study showing slightly lower success rate accounted for induced VBACs? Induction, be it VBAC or first time birth or repeat vaginal birth, does increase the risk of a cesarean, period.

[wombatclay]

I'm a reference librarian (free range at the moment while my munchkin brigade is young) so I looooooove helping people find the information they need... it's almost an obsession of mine.

Some studies do divide out induction as a factor, others don't. It kind of depends on the study but most do take induction into account. Two of the three studies I quote specifically mention induction in their abstracts, the third mentions that they controlled for certain factors but doesn't mention which factors in the abstract (it would be in the full text however).

It's important to remember though that there is a lot of data that isn't captured by the studies. For example, a study generally wont have any information about the "personal" details of the birth... did the woman have the full emotional support of her partner or was she VBACing despite her partner's opposition? Did she have a labor nurse who was really supportive, perhaps a VBAC mother herself, or was her nurse opposed to VBAC, perhaps having had a UR herself or having attended a birth with a UR? Was the care provider someone the birthing mom knew well and trusted, or was this an on call provider she'd never met or the one provider in the practice the mom really didn't get along with? Was she in a comfortable environment or was she feeling flashbacks to her c/s labor experience (with my first vbac I almost ended up in the same birth suite where my first birth had ended in c/s... I requested a different room because I knew it would be too difficult for me to birth in "that" room but that sort of detail certainly wasn't in my medical record!)

I guess what I'm trying to say is you have to take the study results for what they're worth. It's like urban crime statistics being discussed on NPR this morning... the reports can give you a generalized big picture, but they can't tell you the specifics of each and every crime.