I wrote a post in this thread that provides the best information I could find on the risks of scar rupture with a vertical, AKA, "classical" uterine incision. As you can see, it is lower than commonly believed, although it is probably still higher than it would be with a prior transverse uterine incision. I would assume that the same odds would apply to an incision made for fibroid surgery. In that same post, I also wrote about every patient's right to refuse surgery, a right that is not suspended by pregnancy, and I provided a link to a fact sheet on the risks of cesarean surgery, which further strengthens the argument that the choice should be yours. As you have discovered, though--"I have to schedule a cesarean at 39 weeks"--all too often, that right is not honored by obstetricians. I wish I could do more to assist you, but the best I can offer is to affirm that your preference for planning vaginal birth is reasonable, but if you cannot convince your doctors to respect your right to do so, see if you can find another doctor who will.

~ Henci

Good morning,

I am looking for a second opinion.  I am 35yo, FTM, approximately 33weeks.  I have been seeing a group of midwives since the beginning of this pregnancy and planned for a natural, unmedicated L&D.  In 2008, I underwent a myomectomy to remove multiple uterine fibroids.  I provided this information at my first prenatal appointment but the post operative report was not reviewed until this week during a routine 2-week check up.  The midwife had some concerns and had me schedule an appointment the following day with one of the physicians.  I was told that I have a classical uterine incision and because of the risk of dehiscence, I have to schedule a ceasarean at 39 weeks.  My preliminary findings give me no assurance that I have any other option.  This is devastating news for me as I may not conceive again.  I understand the type of incision I have bears a 4% chance of uterine rupture or dehiscence, but what about the other 96%?  Thank you in advance for your response.

Sincerely,

Carissa

I am delighted to hear this! ~ Henci

I just wanted to give a little update.  I did give birth vaginally earlier this week.  My uterus did its job in spite of having multiple scars and a previous diagnosis of 'thin lower uterine segment.'  Hopefully women with this diagnosis will find some comfort in reading this.

Thank you, Henci.  That helps reaffirm what I had already discovered about dehiscence and the limitations of sonographic assessment of the uterine thickness. ~ Kimberly

Whoever told you there is no way to know what implications a thin scar has for a planned VBAC  was on the money. Here are the problems with sonographic measurements:

• Studies used scar "defect" as their outcome. "Defect" includes harmless dehiscences, which we know (see previous posts in this thread) occur more frequently than scar ruptures. In fact, in all but one study, the scar evaluation was made at repeat cesarean, which means we don't know how many VBAC women had an uneventful vaginal birth despite having a "defect."
• While thicker lower uterine segments are less likely to develop defects in labor, i.e. good negative predictability, the positive predictability of thinner ones for defects isn't that great. Furthermore, a pooled analysis of multiple studies could not establish a useful cutoff point because of variability among studies.
• The likelihood of scar rupture is influenced by other modifiable factors such as labor induction, oxytocin augmentation of contractions, single- vs. double-layer uterine closure. Investigators do not account for these in their studies of LUS thickness, which means we have no idea of the isolated effect of thickness in an otherwise optimally treated population. 
• Accuracy of measurement depends on the skill and experience of the ultrasonographer. 

Guise JM, Eden K, Emeis C, et al. Vaginal birth after cesarean: new insights. Evid Rep Technol Assess (Full Rep) 2010(191):1-397.

Jastrow N, Chaillet N, Roberge S, et al. Sonographic lower uterine segment thickness and risk of uterine scar defect: a systematic review. J Obstet Gynaecol Can 2010;32(4):321-7.

Meanwhile, any discussion of planned VBAC vs. planned elective repeat cesarean surgery should take into account the escalating risks of serious maternal and perinatal complications with scar accumulation.

I hope this helps.

~ Henci 

Dear Henci,

I have a related question.  I was "diagnosed" with a thin LUS during a term (39w) repeat cesarean due to double footling breech presentations in both twins.  Twin B flipped breech at 33 weeks; twin A at 37 weeks.  Argh!

My Baby A initiated labor by violently kicking and breaking her amniotic sac.  Labor contrax began 15 minutes later; the cesarean took place about 3 hours after that.

I'm planning for a VBA2C (22 mo. intrapartum interval; age 38; healthy; BMI under 30) and been urged to find an OB.  Local docs are 'behind the times' when it comes to revising their VBAC practices and finding a VBAmC supporter is next to impossible.  VBA2C is still in the SOP for homebirth midwives in my state.

I interviewed an OB last week who agreed to take me if I sign an AMA waiver.  The first words out of his mouth before I even gave him my background were "DON'T DO IT!"  Awesome.

Anyway, he's certain that if I had a thin LUS at term with the twins, that my scar is weaker and more likely to rupture.  I was under the impression that 'back in the day' when docs were palpating VBAC scars, they would leave dehiscences alone because the uterus would heal itself.  What is your impression of "thin LUS" (parchment paper) and implications for my upcoming plans.  Other docs I've talked too about this in the past said there's really no way to "know" what it means.

Many thanks,

Kimberly James

You're welcome! ~ Henci

Dear Henci,

Thank you very much! That helps a lot!

I have a 1992 study of dehiscence, which the authors defined as "silent separation of a scar incidentaly diagnosed at laparotomy or vaginal examination with no fetal or maternal compromise" (p. 540). One woman of 475 (2 per 1000) having a VBAC had a dehiscence detected whereas 19 of 924 (21 per 1000) had one found incidentally at cesarean surgery. I also have a 1989 study distinguishing between dehiscence, which authors defined as "separation of the uterine scar with unruptured membranes" (p. 570), and scar rupture. Six of 1008 women (6 per 1000) had a scar rupture, but 44 of 1105 (40 per 1000) had a dehiscence discovered at either repeat elective cesarean or VBAC ending in cesarean.

~ Henci

Dear Henci,

I know this subject is old, but as it came up on a different board, could you tell me which studies you are referring to in  your last post?

Thank you very much!

You say that a dehiscence is not an excess risk in subsequent labor…

But isn’t such a small window just the beginning of a rupture and would widen with each contraction?

I am trying to see the difference here, because I would really really really like to try a VBAC (my scar ruptured for about 2 inches)

Do you have any research to show me (which I can then show my doctor)?

Thanks!