Scar rupture is the most frequently cited and feared reason for repeat surgery, but the incidence of rupture is minute (Am J Ob Gyn, 1989, 160: 569-73).
Some scars do rupture, but without any symptoms such as bleeding or pain. These are minor ruptures which cause no problems to mother or baby and heal by themselves.
The rate of scar rupture for women undergoing a trial of labour with single, normal babies is measured in fractions of a percent 0.09 to 0.22 per cent for women with a lower segment "bikini line" cut. It is estimated that the risk of a woman requiring a caesarean for true emergency conditions such as placenta praevia, cord prolapse or fetal distress is 2.7 per cent - nearly 30 times greater than the risk of uterine rupture (Effective Care in Pregnancy and Childbirth, 1995, Oxford University Press).
A substantial review of medical literature on vaginal birth after caesarean (VBAC) from 1950 to 1980 found that out of 5,325 recorded VBACs there was not a single maternal death related to uterine rupture (Ob Gyn, 1982; 59: 135). This concurs with other findings.
There is almost no physiological reason to refuse VBAC. Research puts the success rate as high as 90 per cent, depending on the reasons for the previous caesarean (Am Fam Physician, 1988; 37: 167-77; Ob Gyn, 1990; 76 (5 pt 1):750-4). Women most likely to achieve VBACs are those who had surgery for a breech baby (85 per cent). Those who had the operation because of "failure to progress", "fetal distress", fetopelvic disproportion or more than one previous caesarean have achieved a VBAC in 50-75 per cent of cases (Clin Ob Gyn, 1992; 35: 445-56).