Lay summary
In New Zealand, each year 1,500 term babies are born by cesarean section when the mother's cervix is fully dilated. Cesarean at this late stage is more likely to result in harm to mum or baby, compared to cesarean performed earlier in labour. This is because the baby's head is more difficult to deliver, causing increased risk of tearing to the uterus (womb), or low oxygen levels/bruising to the baby. A single use inflatable "balloon" that is inserted vaginally has been marketed as a way of making full dilation cesarean safer for mums and babies. Many doctors both in NZ and overseas have heard about this medical device and started to use it, despite a lack of evidence that it helps. There is no evidence that it causes harm, but at $NZ670 per use, we believe further research is required to determine whether it benefits mums and babies.