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The New Zealand Medical Journal

 Journal of the New Zealand Medical Association, 04-July-2008, Vol 121 No 1277

The maternal outcome in placenta accreta: the significance of antenatal diagnosis and non-separation of placenta at delivery
Hong Soo Wong, John Hutton, Jane Zuccollo, John Tait, Kevin C Pringle
Aim To evaluate the effects of antenatal diagnosis and subsequent placental non-separation at delivery on the maternal outcome in confirmed cases of placenta accreta.
Method The perinatal database and medical records for women who delivered in the period 2000–6 in a teaching hospital in New Zealand with a diagnosis of placenta accreta or postpartum haemorrhage or hysterectomy were reviewed. In confirmed placenta accreta cases, the amount of blood loss and blood transfused at delivery and subsequent emergency hysterectomy were analysed in respect to the presence/absence of antenatal diagnosis and the management at delivery.
Results 16 women had placenta accreta confirmed (15 histologically and 1 visually). Antenatal diagnosis was made in 7 women, elective Caesarean delivery planned in all, hysterectomy to follow in 5 (4 elective, 1 emergency preterm), and elective placental separation in 2 women. When an antenatal diagnosis was not made (n=9), attempted placental separation led to emergency hysterectomy for all (p=0.001). Antenatal diagnosis and placental non-separation resulted in less mean blood loss (1.4 L vs 3.6 L, p=0.003; 1.0 L vs 3.4 L, p<0.001) and mean units of blood transfused (1.2 vs 5.1, p= 0.005) in the latter.
Conclusion In placenta accreta, antenatal diagnosis and avoidance of placental separation may result in better maternal outcome.

Placenta accreta is a well-known cause of maternal morbidity and mortality.1 The incidence of placenta accreta (including increta and percreta) may have risen 10-fold in the past 50 years,2 and recent reports suggest a frequency per delivery between 1:2500 and 1:110.1–3.
The maternal risk appears to occur at the time of placental separation resulting in severe haemorrhage, disseminated intravascular coagulation, massive blood transfusion, need for intensive care, hysterectomy, and occasionally maternal death.4–6
Conservative management by leaving the placenta in situ at the time of delivery has been proposed to lessen the risk of severe haemorrhage and hysterectomy.7–9 However, when conservative management is carried out based on the clinical suspicion of placenta accreta at the time of delivery, there may not be histological confirmation or proof of the condition.7 It is therefore difficult to attribute a better outcome for conservative management to the treatment method alone.
The aim of this retrospective analysis was to determine the incidence of confirmed placenta accreta in our institution and to examine the effects of an antenatal diagnosis and the subsequent non-separation of the placenta during the third stage on maternal outcomes.


Women who delivered in the second and third trimesters in the period 1 January 2000 to 31 December 2006, with a diagnosis of placenta accreta or postpartum haemorrhage or hysterectomy, were identified from a perinatal database at Wellington Hospital (Wellington, New Zealand).
The medical notes were examined and checked with the database for the following:
  • Any confirmation of diagnosis placenta accreta and the basis for the confirmation including clinical observation or histologic findings;
  • The women’s risk factors for placental accreta;
  • Any antenatal diagnosis made by ultrasound and/or magnetic resonance imaging (MRI);
  • The recorded blood loss (litres, measured and estimated);
  • The blood units transfused (around 300 ml per unit);
  • Requirement for other blood products (fresh frozen plasma and/or cryoprecipitate);
  • Intensive Care Unit (ICU) admission;
  • Diagnosis of disseminated intravascular coagulation (DIC);
  • Operative interventions and complications (such as hysterectomy and bladder injuries); and
  • The length of stay after delivery.
The diagnosis of placenta accreta in those women identified was checked against the histological findings by the Pathology Department.
As this retrospective analysis conforms to the standards established by the NHMRC for ethical quality review, ethics approval was not sought.
The statistical software package SPSS 12.0 (SPSS Inc., Chicago, IL, USA) was used for data analysis. Independent samples t-test, Fisher exact test and Mann-Whitney U test were applied where appropriate. A p value <0.05 was regarded as statistically significant.


Sixteen women were identified from the perinatal database, hospital records, and the Pathology Department as having confirmed placenta accreta in this 7-year period during which there were 26,556 deliveries—an incidence of 1 per 1660 deliveries.
Of these 16 women, 15 had histological confirmation (based on hysterectomy specimens in 14, and the placental specimen in 1) and 1 had clinical confirmation by laparotomy with placenta percreta being observed. There were 2 cases of placenta percreta (Cases A and G). The clinical details and the pregnancy outcomes of these sixteen women are listed in Table 1.
There were 4 women with no previous Caesarean section. In the 12 women with previous Caesarean section(s), 4 did not have placenta previa in the index pregnancy. In the remaining 8 patients with previous Caesarean section(s) and placenta previa, the location of the placenta was Type IV (i.e. both anteriorly and posteriorly located) in 3, anterior in 4, and posterior in 1.
Placenta accreta was not screened in the first half of the study period. An antenatal diagnosis of placenta accreta had been made by ultrasound and/or magnetic resonance imaging (MRI) in seven women—six were delivered by elective Caesarean section and one as a preterm emergency because of antepartum haemorrhage.
After effecting delivery of the infant, the placenta was left unseparated in five of these seven women, of whom four had a hysterectomy, and the fifth (Woman A), with placenta percreta, had combined methotrexate treatment and uterine artery embolisation.10
The normal practice of the use of syntocinon bolus after delivery of the infant was avoided in cases where the placenta was not separated electively. The placenta was separated as planned in two of these seven cases at the time of delivery; at elective Caesarean section in a case with antenatal diagnosis of partial placenta accreta (Woman F), and during dissection at elective Caesarean hysterectomy (confirmed placenta percreta histologically) in the other (Woman G). Thus, in the group with an antenatal diagnosis, hysterectomy was planned following Caesarean delivery in five of the seven women, and the uterus was conserved in two.
In nine cases an antenatal diagnosis was not made. Separation of the placenta was attempted in all nine women at the time of delivery (p=0.005) leading to emergency hysterectomy in all (p=0.001). Compared with the group with an antenatal diagnosis of placenta accreta, women who had not had an antenatal diagnosis of placenta accreta had significantly more haemorrhage (mean total blood loss of 3.6 L vs 1.4 L, p=0.003) (Table 2).

Table 2. The maternal outcome in relation to antenatal diagnosis of placenta accreta

Antenatal diagnosis
P value
Yes (n=7)
No (n=9)
Attempted placental separation
Total blood loss (litres) (mean ± SD)
Number of units of blood transfused
Other blood products required
Emergency hysterectomy
Bladder injury
ICU admission
Length of postnatal stay (days) (mean ± SD)
1.4 ± 1.0
2.3 ± 2.9
8.6 ± 4.9
3.6 ± 1.3
5.1 ± 2.9
9.9 ± 9.3
*Statistically significant; †2-tailed independent sample t-test not assuming equal variance; ‡2-tailed Fisher Exact Test; ¶2-tailed Mann-Whitney U test; DIC=disseminated intravascular coagulation; SD=standard deviation.

Attempts at placental separation were made in 11 women (Table 1 and 3).
Two of these 11 women had been diagnosed with accreta antenatally as described above. These 11 women had significantly more blood loss (3.4 L vs 1.0 L, p <0.001) and more units of blood transfused (5.1 units vs 1.2 units, p=0.005) compared to the 5 women who had an antenatal diagnosis but had hysterectomy without attempted placenta separation (4), or had the placenta left in situ with methotrexate therapy and uterine artery embolisation (Woman A)10 (Table 3).

Table 3. The maternal outcome in relation to attempted placental separation at delivery

Placental separation
P value
Yes (n=11)
No (n=5)
Total blood loss (litres) (mean ± SD)
Number of units of blood transfused
Other blood product required
Emergency hysterectomy
Bladder injury
ICU admission
Length of postnatal stay (days) (mean ± S.D.)
3.4 ± 1.5
5.1 ± 2.9
9.6 ± 8.5
1.0 ± 0.5
1.2 ± 1.6
8.8 ± 5.6
*Statistically significant; †2-tailed independent sample t-test not assuming equal variance; ‡2-tailed Fisher Exact Test; ¶2-tailed Mann-Whitney U test; DIC=disseminated intravascular coagulation; SD=standard deviation.

There were two bladder injuries: in one the injury occurred at elective hysterectomy after an antenatal diagnosis (a case of placenta percreta, injury related to disease pathology), and the other from dissection of the lower segment of the uterus at emergency hysterectomy, and this was considered to be related to a previous Caesarean section rather than the placenta accreta. The use of ureteric stent was useful intraoperatively when bladder involvement was suspected.
Three women who had had placental separation developed infection postnatally, and all three did not have an antenatal diagnosis of placenta accreta. In two woman, intrauterine infection occurred after the placenta was removed partially; one following a vaginal delivery and hysterectomy was required 2 weeks post delivery due to recurrent haemorrhage (Woman N), and the other following an elective Caesarean section for placenta previa and the adherent portion of placenta was removed by hysterectomy four weeks later (Woman P). In the third woman, vault infection followed hysterectomy that was performed for severe haemorrhage at manual removal of placenta after a second trimester abortion.
No other significant morbid associations were noted (Table 2 and Table 3).


In a recent study7 where conservative management of placenta accreta was reported to be associated with less maternal morbidity, the diagnosis of placenta accreta was made either clinically or histologically. This retrospective analysis showed that there were 16 cases of confirmed placenta accreta in the seven year study period in our institution—15 histologically and one on direct observation at laparotomy (a case of placenta percreta where the obtaining of a specimen for histologic confirmation would have been hazardous). The incidence of placenta accreta in our study of 1:1660 was within the range of other reports.1–3
Hysterectomy was undertaken in most of the women (14 of 16) either electively or as an emergency. All but one had had children previously (Woman L, in whom hysterectomy was performed as a life-saving procedure due to severe haemorrhage).
In nearly half of our cases, the diagnosis of placenta accreta was made antenatally. An antenatal diagnosis allowed patient counselling and management to be planned, including the choice and timing of elective delivery, the decision as to whether to separate the placenta at the time of delivery and the use of prophylactic or alternative strategies (e.g. internal iliac artery ligation at the time of surgery, uterine artery embolisation, and the use of methotrexate after delivery).11
The degree of haemorrhage in this group of patients was low and resulted in a decreased risk of emergency/unplanned hysterectomy.
In all our cases, the deliveries or the third stage were supervised by obstetric consultants because of the presence of risk factors of placenta accreta (e.g. placenta previa or previous Caesarean section).1,3,4 Four units of blood were made available routinely when the patient was at high risk or diagnosed of placenta accreta. In each of the 9 cases where placenta accreta was not diagnosed antenatally, heavy bleeding resulted from attempted placental separation at the time of delivery.
Efforts to arrest bleeding (including the use of syntocinon, prostaglandin or uterine sutures) were often made before resorting to emergency hysterectomy, and may account for the significantly larger amount of blood loss and blood transfused in this group.
In the second half of the study period, screening of placenta accreta in women with identifiable risk factors allowed antenatal diagnosis and planned management, with better clinical outcome observed. An antenatal diagnosis of placenta accreta can be made with ultrasound and/or MRI.12–21
The reported diagnostic criteria ultrasound include marked thinning/absence12 or obliteration13 of the retroplacental hypoechoic/clear zone/space,12,13 thinning, irregularity or focal disruption of the hyperechoic uterine serosa-bladder wall complex,12 or the posterior bladder wall-uterine interface,13 the presence of a focal exophytic mass with the same echogenicity as placenta beyond the uterine serosa,12 placental lacunae,12–14 myometrial thickness of <1 mm,14 placental-uterine wall interface-disruption,15 placental lacuna flow,16,17 prominent subplacental venous complex,17 bladder-uterine serosa interface hypervascularity,17 vessels extending from placenta to bladder,18 vessels bridging from placenta to margin of uterus,18 and vessels crossing interface-disruption sites.15
A diagnosis with ultrasound (+/– Doppler) has been reported to have a sensitivity ranging from 33 to 100% and a specificity of 79 to 100% using various sonographic diagnostic criteria in combination.12–19 The sensitivity of individual criterion (placenta lacunae, absence of the retroplacental clear zone and interruption of posterior bladder wall-uterine interface) varies from 7% to 93% in one report.13
The diagnosis on MRI relies on evidence of placental invasion into the myometrium.20 The use of MRI has a variable sensitivity ranging from 38 to 88%19,21 and specificity of up to 100% when it is applied as a secondary diagnostic tool.18,21 However, ultrasound is used more widely and the cost is lower compared with MRI.
The variable sensitivity and specificity of ultrasound suggests the need for the identification of more specific sonographic criteria for antenatal diagnosis of placenta accreta15 and the possible incorporation of screening for this condition in high-risk patients.13,15,18
Often placenta accreta is not known before delivery (as noted in 9 out of the 16 cases in this series) and placental separation has already been attempted before placenta accreta is recognised. The management options are to withhold further separation followed by treatment with other conservative measures or to continue with placental separation until the uterine cavity is “empty.”
Withholding repeated attempts at placental separation appears a feasible option from previous reports and may result in conservation of the uterus and subsequent fertility in this situation.7,8
Although separation of the placenta in our study was shown to be associated with an increased amount of blood loss and risk of emergency hysterectomy, separation of placenta was attempted successfully in Woman F with an antenatally diagnosed partial placenta accreta and no hysterectomy was required. There are situations where placental separation may be the preferred option of management, for instance, when the facilities for monitoring or resuscitation in case of severe haemorrhage are not readily available for geographical reasons.
Risks of conservative management have been reported, including recurrent haemorrhage,22 DIC,22,23 infection,7,24 need for curettage,22 and ultimately hysterectomy.22–24
The reliability of the exact incidence of these complications and the success rate with conservative management are difficult to assess because of the lack of confirmation of the diagnosis in cases managed conservatively. For this reason it is difficult to compare the pregnancy outcome between surgically managed and conservatively managed placenta accreta. We have chosen to avoid this by limiting only to confirmed cases in this analysis, giving us just a small number of cases.
Despite the limitations by the small number of total and conservatively managed cases, the relationship between improved maternal outcome with antenatal diagnosis of placenta accreta and non-separation of placenta was clearly shown.
The assessment of the site and extent of placenta accreta antenatally has been demonstrated to be possible with the use of MRI20 and ultrasound.10,25,26 If screening for placenta accreta in high-risk patients and accurate antenatal diagnosis and assessment could be effected reliably, this could allow a management strategy to be planned, and placental separation possibly avoided in indicated cases. Such management may be associated with less blood loss, less need for blood transfusion and a decreased risk of emergency hysterectomy.


Antenatal diagnosis of placenta accreta allows planned management and is associated with an improved maternal outcome in terms of decreased blood loss at delivery and decreased emergency/unplanned hysterectomy. These effects are more marked when placental separation is not attempted in the presence of an antenatal diagnosis, resulting in less need for blood transfusion as well.
Competing interests: None known.
Author information: Hong Soo Wong, Senior Lecturer1; Jane Zuccollo, Senior Lecturer1; John Hutton, Professor1; Kevin C Pringle, Professor1; John Tait, Clinical Director2
  1. Department of Obstetrics and Gynaecology, School of Medicine and Health Sciences, University of Otago, Wellington
  2. Women’s Health Service, Capital and Coast District Health Board, Wellington
Acknowledgement: We thank Mr Gabriel Sertsou (Statistician, University of Otago) for his advice on statistical analysis.
Correspondence: Dr Hong Soo Wong, Senior Lecturer, c/o Department of Obstetrics and Gynaecology, School of Medicine and Health Sciences, University of Otago, Wellington, PO Box 7343, Wellington South, New Zealand; Fax: +64 (0)4 3855943; email:
  1. Gielchinsky Y, Rojansky N, Fasouliotis SJ, Ezra Y. Placenta accreta—summary of 10 years: a survey of 310 cases. Placenta. 2002;23:210–4.
  2. ACOG Committee on Obstetric Practice. ACOG Committee opinion. Number 266, January 2002: placenta accreta. Obstet Gynecol. 2002;99:169–70.
  3. Wu S, Kocherginsky M, Hibbard JU. Abnormal placentation: twenty-year analysis. Am J Obstet Gynecol. 2005;192:1458–61.
  4. Usta IM, Hobeika EM, Musa AA, et al. Placenta previa-accreta: risk factors and complications. Am J Obstet Gynecol. 2005;193:1045–9.
  5. Hall MH. Haemorrhage. In: Lewis G, editor. Why mothers die 2000-2002. 6th report of confidential enquires into maternal deaths in the United Kingdom. London: RCOG Press; 2004.
  6. O'Brien JM, Barton JR, Donaldson ES. The management of placenta percreta: conservative and operative strategies. Am J Obstet Gynecol. 1996;175:1632–8.
  7. Kayem G, Davy C, Goffinet F, et al. Conservative versus extirpative management in cases of placenta accreta. Obstet Gynecol. 2004;104:531–6.
  8. Kayem G, Pannier E, Goffinet F, et al. Fertility after conservative treatment of placenta accreta. Fertil Steril. 2002;78:637–8.
  9. Legro RS, Price FV, Hill LM, Caritis SN. Nonsurgical management of placenta percreta: a case report. Obstet Gynecol. 1994;83:847–9.
  10. Wong HS, Parker S. Ultrasonographic findings in conservatively treated placenta percreta. Ultrasound Obstet Gynecol. 2005;26:580–1.
  11. Placenta praevia and placenta praevia accreta: diagnosis and management. RCOG Guideline No. 27, 2005.
  12. Finberg HJ, Williams JW. Placenta accreta: prospective sonographic diagnosis in patients with placenta previa and prior cesarean section. J Ultrasound Med. 1992;11:333–43.
  13. Comstock CH, Love JJ Jr, Bronsteen RA, et al. Sonographic detection of placenta accreta in the second and third trimesters of pregnancy. Am J Obstet Gynecol. 2004;190:1135–40.
  14. Twickler DM, Lucas MJ, Balis AB, et al. Color flow mapping for myometrial invasion in women with a prior cesarean delivery. J Maternal Fetal Med. 2000;9:330–5.
  15. Wong HS, Cheung YK, Strand L, et al. Specific sonographic features of placenta accreta: tissue interface disruption on greyscale imaging and evidence of vessels crossing interface-disruption sites on Doppler. Ultrasound Obstet Gynecol. 2007;29:239–41.
  16. Lerner JP, Deane S, Timor-Tritsch IE. Characterization of placenta accreta using transvaginal sonography and color Doppler imaging. Ultrasound Obstet Gynecol. 1995;5:198–201.
  17. Chou MM, Ho ES, Lee YH. Prenatal diagnosis of placenta previa accreta by transabdominal color Doppler ultrasound. Ultrasound Obstet Gynecol. 2000;15:28–35.
  18. Levine D, Hulka CA, Ludmir J, et al. Placenta accreta: evaluation with color Doppler US, power Doppler US, and MR imaging. Radiology. 1997;205:773–6.
  19. Lam G, Kuller J, McMahon M. Use of magnetic resonance imaging and ultrasound in the antenatal diagnosis of placenta accreta. J Soc Gynecol Invest. 2002;9:37–40.
  20. Kirkinen P, Helin-Martikainen HL, Vanninen R, Partanen K. Placenta accreta: imaging by gray-scale and contrast-enhanced color Doppler sonography and magnetic resonance imaging. J Clin Ultrasound. 1998;26:90–4.
  21. Warshak CR, Eskander R, Hull AD, et al. Accuracy of ultrasonography and magnetic resonance imaging in the diagnosis of placenta accreta. Obstet Gynecol. 2006;108:573–81.
  22. Jaffe R, DuBeshter B, Sherer DM, et al. Failure of methotrexate treatment for term placenta percreta. Am J Obstet Gynecol 1994;171:558–9.
  23. Silver LE, Hobel CJ, Lagasse L, et al. Placenta previa percreta with bladder involvement: new considerations and review of the literature. Ultrasound Obstet Gynecol. 1997;9:131–8.
  24. Bader G, Jelen H, Quarello E, Interest of modern imagery for conservative management of a placenta percreta. Gynecol Obstet Fertil. 2007; 35:142–8.
  25. Wong HS, Zuccollo J, Parker S, et al. Antenatal diagnosis of non-previa placenta increta with histological confirmation. Ultrasound Obstet Gynecol. 2006;27:467–9.
  26. Wong HS, Zuccollo J, Strand L, et al. The use of ultrasound in assessing the extent of myometrial involvement in partial placenta accreta. Ultrasound Obstet Gynecol. 2007;30:227–30.
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