Placenta accreta is a condition where chorionic villi from the placenta have grown down into the muscles of the uterus and there is no clear separation between the placenta and the wall of the uterus. This means that the placenta cannot be easily removed without risk of torrential haemorrhage, which can kill the mother, or perhaps her life can only be saved by an emergency hysterectomy.
The condition occurs more often when there is placenta praevia (i.e. the placenta is placed low down in the womb where it may partially or totally obstruct the baby’s entrance to the birth canal)
A recent study from Saudi Arabia looked at risk factors. In 23,000 deliveries 100 women had placenta praevia and 12 of them had placenta praevia accreta. A woman’s age or the number of children she had made no difference to the risk.
The risk went up when the woman had had a previous caesarean – and the more caesareans, the higher the risk. 75% of the accreta cases had had a caesarean. The percentage of placenta praevias which were embedded increased from 4.1% in women with no previous section, to 60% in patients who had three or more caesars. One of the patients died from a massive haemorrhage – she had had two previous sections.
This is the latest in a number of studies which show that caesarean section increases the risk of both placenta praevia and placenta accreta in subsequent pregnancies. As our caesarean rate rises, the number of women at risk of massive haemorrhage, emergency hysterectomies, and maternal death, increases too.
- Zaki, M, et al, Risk factors and morbidity in patients with placenta previa accreta compared to placenta previa non-accreta, Acta Ob Gyn Scand, 1998; 77: 391-4.
- See also Caesareans cause placenta praevia and accreta from the Winter 1999/2000 AIMS Journal.