VBAC: Slow Dilation May Warn of Rupture

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This is not new news: it has been known for many years that women who dilate slowly during a VBAC labour are at an increased risk of uterine rupture. This study confirms what we know. The question is: how slow too too slow? Some midwives and obstetricians talk in terms of VBAC labour lasting no more than 12 hours. I think that an arbitrary time limit is unhelpful, because there is a difference between no progress over a period of time, and slow progress over a period of time. So long as some progress is being made and the mother and baby are well, there is no reason not to continue with a VBAC labour, well-supported and encouraged in a natural, active birth.

Women with a previous cesarean delivery who attempt a vaginal delivery during a subsequent birth may be at risk for uterine rupture, depending on their rate of cervical dilation ...

In a retrospective study, the time to progress 1 cm of dilation was similar between the study group and controls, until 7 cm of dilation ... at 7 cm dilation, women who experienced uterine rupture spent significantly longer times progressing 1-cm in dilation compared to controls -- median hours from 7 cm to 8 cm was 0.39 versus 0.15 ...

... Between 7 cm and 8 cm, the 95th percentile for women with a successful attempt at labor was 0.70 hours, compared with 1.57 hours for those who ruptured.

From 8 cm to 9 cm, the 95th percentile of time for progression was 0.38 and one hour for the two groups, respectively ...

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