Hi,
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The attempt of vaginal delivery after previous C-section not done due to chances of having scar rupture and leading to uterine rupture (life threatening complication for both mother and baby). If there has been more than 3 years gap and if there is no scar tenderness, then properly supervised vaginal delivery attempt (VBAC) can be made (with facility of emergency C-section and neonatologist at hand). There are evidence that about 60-80% of women have had successful VBAC (vaginal birth after Cesarean). The chances of success also depend on baby growth/weight, maternal pelvis, no previous surgeries on uterus (like myomectomy etc), no other medical or obstetric problems. Discuss in detail with your treating gynecologist about your candidacy (along with risks and benefits involved) for VBAC.
Take care.