Practice Bulletin 184
ACOG recently released Practice Bulletin number 184 about VBAC, to replace number 115. Here's what it had to say about special scars. Overall, nothing much has changed. ACOG still will not sanction VBAC under most circumstances, yet still doesn't have a rupture rate for most of us. While they have thankfully moved away from the inflated and unsubstantiated 4-9% for classical, inverted T, and J scars, they did not replace it with a new number. The one special scar exception is low vertical. As long as it is contained within the lower uterine segment, a low vertical scar has long been acceptable for VBAC.
"The preponderance of evidence suggests that most women with one previous cesarean delivery with a low-transverse incision are candidates for and should be counseled about and offered TOLAC. Conversely, those at high risk of uterine rupture (eg, those with a previous classical or T-incision, prior uterine rupture, or extensive transfundal uterine surgery) and those in whom vaginal delivery is otherwise contraindicated (eg, those with placenta previa) are not generally candidates for planned TOLAC. However, individual circumstances must be considered in all cases. For example, if a patient who may not otherwise be a candidate for TOLAC presents in advanced labor, the patient and her obstetrician or other obstetric care provider may judge it best to proceed with TOLAC."
Barring an early, spontaneous, and very short labor, those with special scars are left with patient autonomy to make their case. The bulletin does go on to point out that many factors come into play, including future fertility and the cumulative risks of multiple c-sections, as well as different values and comfort levels with risks.
With regard to prior ruptures, the bulletin leaves much to be desired. Two of the references given were retrospective studies with very small sample sizes and were over 45 years old. The number of practices that have changed in that amount of time brings into question the relevance of including these references. The other reference was from 2015 and included 46 women who had a 15% rerupture rate. The recommendation was for late preterm or early term delivery.
There was no mention of myomectomy in the bulletin.
"After counseling, the ultimate decision to undergo TOLAC or a repeat cesarean delivery should be made by the patient in consultation with her obstetrician or other obstetric care provider. The potential risks and benefits of both TOLAC and elective repeat cesarean delivery should be discussed. Documentation of counseling and the management plan should be included in the medical record. Checklists are helpful guides for documentation of counseling and management. Information is available on ACOG’s For More Information web page. Global mandates for TOLAC are inappropriate because individual risk factors are not considered."
This, as I see it, is the best recourse we might have as less-than-ideal VBAC candidates. If, after all the counseling and discussion, our own values and risk tolerances differ from that of our providers, that can be documented and a plan to move forward put in place.
I call on ACOG to collect more data. The percentage of women with special scars is small enough that each woman's outcome greatly affects the overal statistic. The general consensus has been on of "asked and answered." That is, anything other than a low transverse scar disqualifies a woman for VBAC. These scars are consistently excluded from VBAC trials, so data is extremely limited. Yet, what data there is has been applied liberally. We can do better.