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PRU-MHC: Policy Research Unit in Maternal Health & Care (2010 - 2018)

Surveillance of placenta accreta

Placenta accreta refers to a group of uterine diseases which are characterised by an abnormally adherent placenta. This group of conditions arise from abnormal placentation where the placental chorionic villi interdigitate with the surface or invade the myometrium in the absence of an intervening decidual plate. As a consequence the pathologically adherent placenta fails to separate from the uterine wall during the third stage of labour. The associated haemorrhage can be torrential and leads to death in some cases still. Whilst improved strategies to resuscitate women are now available placenta accreta nevertheless often necessitates emergency, life-saving management, the options for which include arterial occlusion, embolisation or ligation, or hysterectomy, the latter with its associated loss of future fertility. Where it is essential to attempt to retain fertility potential, and provided not contraindicated by the extent of haemorrhage, the intact placenta or pieces of retained placenta may be left in situ.The aim of this study was to describe the risk factors, management and outcomes of the condition in a national cohort.

Key findings

  • 134 women with placenta accreta/increta/percreta were identified, in 50% of whom (66/133) the condition was suspected antenatally.
  • The estimated incidence of placenta accreta/increta/percreta was 1.7 per 10,000 maternities overall; 577 per 10,000 in women with both a previous caesarean delivery and placenta praevia.
  • Women who had a previous caesarean delivery (adjusted odds ratio (aOR) 14.41, 95%CI 5.63-36.85), other previous uterine surgery (aOR 3.40, 95%CI 1.30-8.91), an IVF pregnancy (aOR 32.13, 95%CI 2.03-509.23) and placenta praevia diagnosed antepartum (aOR 65.02, 95%CI 16.58–254.96) had raised odds of having placenta accreta/increta/percreta. There was also a raised odds of placenta accreta/increta/percreta associated with older maternal age in women without a previous caesarean delivery (aOR 1.30, 95%CI 1.13-1.50 for every one year increase in age).
  • This study shows that women with both a prior caesarean delivery and placenta praevia have a high incidence of placenta accreta/increta/percreta. There is a need to maintain a high index of suspicion of abnormal placental invasion in such women and preparations for delivery should be made accordingly.
  • Women identified antenatally had lower levels of haemorrhage (median blood loss 2750ml versus 6100ml, p=0.008) and were less likely to receive a blood transfusion (59% versus 94%, p=0.014) than women in whom the diagnosis was not suspected antenatally.
  • Women diagnosed antenatally were more likely to receive preventive therapies for haemorrhage.
  • Women in whom no attempt was made to remove the placenta, either prior to hysterectomy or prior to conservative management, had lower estimated blood loss (median 1750ml versus 3700ml, p=0.001) and fewer received a blood transfusion (57% versus 86%, p < 0.001) than women in whom an attempt was made to remove the placenta.
  • These findings support current RCOG and other guidelines which recommend that if the placenta fails to separate, no attempt is made to remove it prior to a planned attempt at uterine conservation or hysterectomy.
NPEU Contact:
Marian Knight (