Why does postpartum haemorrhage happen?

PPH can be caused by a number of factors.

• The uterus not contracting properly.
• Problems with the placenta not coming away from the wall of the uterus.
• Injury to the uterus or genital tract (e.g. episiotomy).
• Blood clotting problems.

Reasons for a PPH

1) The uterus not contracting properly.

The uterus is a large muscle which needs to contract after the baby is born. Sometimes the uterus lacks the muscle tone to contract effectively. This could be because:

• The uterus has been stretched or overdistended during pregnancy.
• Where there is a large baby (macrosomia).
• Where there has been a multiple pregnancy.
• Excess amount of amniotic fluid (polyhydramnios).
• The uterus has become exhausted during the labour, such as after a very long labour, a very quick labour or a labour which has been speeded up with drugs.

2) Problems with the placenta.

Sometimes the uterus is prevented from contracting because there is some obstruction preventing it becoming smaller. This could be because:

• There is a problem with the placenta coming away from the wall of the uterus, for example where there is a placenta accreta or retained placenta.
• There is a blood clot preventing the uterus from contracting.

3) Injury to the uterus or genital tract.

Sometimes injuries can happen during the birth process which may result in bleeding. In these cases, the blood is not coming from the placental site and the uterus may be well contracted. The damage could be to the uterus, cervix, birth canal or due to an episiotomy or tear in the perineum.

4) Blood clotting problems.

These could be as a result of:

• Hereditary clotting problems.
• Clotting problems acquired during pregnancy.
• Anti-coagulant therapy.