A placental abrution is when the placenta separates from the wall of the uterus before the baby is born. Sometimes only a small amount of the placenta separates so that there is enough working placenta left to continue to nourish and provide oxygen for the baby. But sometimes an abruption is life-threatening as the baby no longer has an adequate oxygen supply. There is also a risk of haemorrhage for the woman. In the severe cases, the baby must be born as soon as possible and this is usually done by emergency caesarean section. Placental abruptions are more common in women who have high blood pressure, but they are, thankfully, very rare, even in women with pre-eclampsia. However, having had one before, you are at increased risk of having an abruption this time. I can't give you any figures for the incidence of placental abruption in labour, but I do know that it is extremely rare. I can tell you that if an abruption happened outside a hospital environment, this will affect the chances of the baby surviving simply because of the time it takes to get to hospital and diagnose the problem. If you were to have an abruption during labour in hospital, the facilities would be there for an immediate emergency caesarean section.