ercent. A woman who had a C-section following a vaginal birth is much more likely to opt for a VBAC than a woman who has never had a vaginal birth. Women having a vaginal birth after a VBAC are likely to have a successful birth. Women who had a C-section for a non-recurring reason, e.g. breech or fetal distress, have higher VBAC success rates than women who have C-sections for such reasons as cephalopelvic disproportion (CPD) or failure to progress (FTP).
Some doctors insist on pelvimetry after a CPD caesarian to try and predict whether a VBAC is likely to be successful or not (Kmom, 2001). However, one study found that 55 percent of women who were found to have an inadequate pelvis by postpartum xray pelvimetry went on to have a successful VBAC. This suggests that pelvimetry is not a useful tool for predicting VBAC success. When carefully reviewed in one study, only 84 women out of 42,793 actually met the strict criteria for CPD diagnosis. Of these, 40 women with strictly defined CPD had a Trial of Labor (TOL) and 68 percent had a vaginal birth. Also, many cases of CPD are actually caused by baby malposition, and many VBAC mothers have given birth vaginally to babies who were larger than their CPD babies.
Many physicians now believe that women with prior C-sections for CPD should not be denied TOL unless there is gross malformation, previous serious pelvic injury, or extreme malnutrition (Kmom, 2001). Success rates for women having a VBAC following a C-section for CPD averages 66 percent and in some studies were found to be as high as 80 percent. Many women have even had successful VBA2Cs after two previous C-sections for CPD. This shows that VBAC are still quite successful after repeating contraindications such as CPD.
For many years, it was thought that babies larger than 9 pounds would distend the uterus excessively and so predispose it to uterine rupture, so a TOL was prohibited for women whose babies wer...