They found that of 969,163 confinements, there were 161 cases of uterine rupture, or an incidence of one in 6,250. All four ruptures in women with two previous sections occurred prior to labour, as did all but one of the 11 cases of previous classical section. In an interview, Dr. Calder stressed his team has yet to determine how many women with a previous C-section actually went through labour. They can therefore only compare the overall rate of rupture against the pregnant population as a whole, but can't specify the risk of the scar coming apart if a women with a previous C-section goes through labour. He has made a broad estimate, however, that the risk for a woman with one previous lower segment scar who undergoes labour would be about one case in 300.
Rupture can occur with a scarred uterus or an intact uterus.
For this reason, the two categories should be considered differently, he added. In Dr. Calder's view, the rising number of C-sections has become a vicious circle in modern obstetrics. The whole thing just spirals. He cited the preferences of mothers, who may be dubious of having another arduous yet unsuccessful labour, as a contributing factor in the increasing number of C-sections. The mothers' views are now having much more impact.