As we know, the risks of cesareans increase with each surgery which is why family size should be considered when evaluating your post-cesarean birth options. Couple that fact with the results of Mercer (2008) which found that successful VBAC also provides a level of protection to future deliveries.
Mercer found that not only do the risks of uterine rupture, uterine dehiscence and other peripartum complications decrease after the first VBAC, but “VBAC success increased with increasing number of prior VBACs” to rates over 90% for women with two or more prior VBACs. They also found that while two or more VBACs did not decrease the risk of rupture further (so a scarred mom’s risk of rupture never goes down to the risk of an unscarred mom), it’s important to note that the risk of rupture did not increase with subsequent VBACs as women are sometimes told in an effort to obtain their consent for a repeat cesarean.
This is one of many studies that the journal Obstetrics & Gynecology provides to the public, full-text, for free without registration.
Mercer, B. M., Gilbert, S., Landon, M. B., & Spong, C. Y. (2008). Labor Outcomes With Increasing Number of Prior Vaginal Births After Cesarean Delivery. Obstetrics & Gynecology , 11, 285-91. Retrieved from http://journals.lww.com/greenjournal/Fulltext/2008/02000/Labor_Outcomes_With_Increasing_Number_of_Prior.6.aspx
OBJECTIVE: To estimate the success rates and risks of an attemptedvaginal birth after cesarean delivery (VBAC) according to thenumber of prior successful VBACs.
METHODS: From a prospective multicenter registry collectedat 19 clinical centers from 1999 to 2002, we selected womenwith one or more prior low transverse cesarean deliveries whoattempted a VBAC in the current pregnancy. Outcomes were comparedaccording to the number of prior VBAC attempts subsequent tothe last cesarean delivery.
RESULTS: Among 13,532 women meeting eligibility criteria, VBACsuccess increased with increasing number of prior VBACs: 63.3%,87.6%, 90.9%, 90.6%, and 91.6% for those with 0, 1, 2, 3, and4 or more prior VBACs, respectively (P uterine rupture decreased after the first successful VBAC anddid not increase thereafter: 0.87%, 0.45%, 0.38%, 0.54%, 0.52%(P=.03). The risk of uterine dehiscence and other peripartumcomplications also declined statistically after the first successfulVBAC. No increase in neonatal morbidities was seen with increasingVBAC number thereafter.
CONCLUSION: Women with prior successful VBAC attempts are atlow risk for maternal and neonatal complications during subsequentVBAC attempts. An increasing number of prior VBACs is associatedwith a greater probability of VBAC success, as well as a lowerrisk of uterine rupture and perinatal complications in the currentpregnancy.
LEVEL OF EVIDENCE: II