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									Canterbury DHB                                                        Women’s & Children’s Health



Placenta praevia involves implantation of the placenta over the internal cervical os. Variants
include complete implantation over the os (total placenta praevia), a placental edge partially
covering the os (partial placenta praevia) or the placenta approaching the border of the os
(marginal placenta praevia).


Placenta praevia occurs in 0.3-0.5% of all pregnancies. The risks increase 1.5- to 5-fold with a
history of caesarean delivery. With an increased number of caesarean deliveries, this risk can be
as great as 10%.

Definition – Types 1 and 2 MINOR, Types 3 and 4 MAJOR

Type 1: Low Implantation
•    Lower placenta margin dips into lower uterine segment
•    Edge lies within 2 to 3.5 cm of internal cervical os

Type 2: Marginal Placenta
•    Placenta within 2 cm of internal os, but does not cover os

Type 3: Partial Praevia
•    Placenta covers internal os when closed
•    Placenta does not cover os when fully dilated

Type 4: Complete Praevia (Central Praevia)
•    Placenta covers internal os even when fully dilated

                                SCREENING AND DIAGNOSIS

While clinical acumen remains vitally important in suspecting and managing placenta praevia,
the definitive diagnoses of most low-lying placentas is now achieved with ultrasound imaging.
Clinical suspicion should, however, be raised in any woman with vaginal bleeding and a high
presenting part or an abnormal lie, irrespective of previous imaging results.

Ultrasound Imaging in Screening for Low-Lying Placenta and Diagnosing Placenta Praevia

Transvaginal ultrasound is safe in the presence of placenta praevia and is more accurate than
transabdominal ultrasound in locating the placenta.
A further transvaginal scan is required for all women whose placenta reaches or overlaps the
cervical os at their anomaly scan as follows:
•     Women who bleed should be managed individually according to their needs.
•     In cases of asymptomatic suspected minor praevia, follow-up imaging can be left until 36

W&CH/GL/M/0002                               Page 1 of 5                    Created: February 2008
Protocol Development: Dr Dianne Poad, CD Obstetrics
Canterbury DHB                                                          Women’s & Children’s Health

•    In cases with asymptomatic suspected major placenta praevia, a transvaginal ultrasound
     scan should be performed at 32 weeks, to clarify the diagnosis and allow planning for third-
     trimester management and delivery.

Diagnosis of a Morbidly Adherent Placenta

Antenatal imaging by colour flow Doppler ultrasonography should be performed in women with
placenta praevia who are at increased risk of placenta accreta. Women with placenta praevia are
at increased risk of having a morbidly adherent placenta if they have an anterior placenta praevia
and have previously been delivered by caesarean section, especially when there has been a short
caesarean to conception interval. Antenatal imaging can help to establish a diagnosis in such
cases and techniques used include ultrasound imaging with colour flow Doppler. Previous studies
estimate sensitivity around 80% and specificity of 96%. MRI by comparison was around 30 –

Imaging antenatally allows for preparation for surgery but false positives do occur and the
diagnosis should be confirmed intraoperatively to avoid inappropriate treatment.

                                ANTENATAL MANAGEMENT

Women with major placenta praevia who have previously bled should be admitted and managed
as inpatients from 34 weeks of gestation. Those with major placenta praevia, who remain
asymptomatic, having never bled, require careful counselling before contemplating outpatient
care. Any home-based care requires close proximity to the hospital, the constant presence of a
companion, and full informed consent from the woman.

For an uncomplicated pregnancy, continue expectant management until an episode of bleeding
occurs. Studies have not shown any difference regarding maternal or fetal morbidity with home
management versus hospitalization, prior to the first bleed. If, however, bleeding or contractions
occur, the patient must rapidly go to the hospital for evaluation. If bleeding persists, preparation
for immediate surgery is indicated. However, if bleeding is minimal and fetal reassurance is
noted, expectant management may be considered to allow for fetal maturity. Additionally,
tocolytics may also be considered in cases of minimal bleeding and extreme prematurity to
administer antenatal corticosteroids. If more that one episode of bleeding occurs during gestation
(at viability or >24 wk), the clinician should consider hospitalization until delivery given the
increased potential for placental abruption and fetal demise.

Sterile speculum examination is appropriate to assess for possible rupture of membranes. Digital
examination should not be undertaken.

Prolonged inpatient care can be associated with an increased risk of thromboembolism. Patients
should be encouraged to remain mobile and the use of prophylactic thromboembolic stockings
should be considered. Prophylactic low molecular weight heparin may be appropriate for women
who are considered to be at high risk of thrombo-embolism for other reasons.

Four units of Cross matched blood should be available for women once inpatient.

W&CH/GL/M/0002                               Page 2 of 5                      Created: February 2008
Protocol Development: Dr Dianne Poad, CD Obstetrics
Canterbury DHB                                                           Women’s & Children’s Health


The mode of delivery should be based on clinical judgment supplemented by sonographic
information. A placental edge less than 2 cm from the internal os is likely to need delivery by
caesarean section. Posterior placenta praevia where the presenting part is prevented from
entering the pelvis may be an indication for caesarean at more than 2 cm from the cervical os.

There is no evidence to support the use of autologous blood transfusion for placenta praevia. Cell
salvage may be considered in cases at high risk of massive haemorrhage.
The choice of anaesthetic technique for caesarean section for placenta praevia must be made by
the anaesthetist, in consultation with the obstetrician and mother, but there is increasing evidence
to support the safety of regional blockade.

An experienced Obstetrician should be present at the time of delivery for major placenta praevia.

                         SURGERY IN THE PRESENCE OF

Placenta accreta is more common, partly related to the increasing caesarean section rate, but also
as a result of increasing maternal age, and increased prior uterine surgery, usually as a result of
termination of pregnancy. Thirty years ago, accreta occurred in approximately 1/30 000
deliveries. Placenta accreta is now thought to occur in approximately 1/500 deliveries.

Women with placenta praevia who have had a previous caesarean section are at high risk of
having a morbidly adherent placenta and should have been imaged antenatally. When placenta
accreta is thought to be likely, consultant anaesthetic and obstetric input are vital in planning and
conducting the delivery. Crossed matched blood should be available and colleagues from other
specialties/subspecialties may be alerted to be on standby to attend as needed.

Conservative management of placenta praevia accreta can be successful and can preserve
fertility, but is considered to be investigational.


Interventional radiology can also be used as a prophylactic measure where there is a known or
suspected case of placenta accreta, such as placenta praevia on previous caesarean section scar,
or placenta accreta diagnosed by scan/colour Doppler or magnetic resonance imaging. Balloons
are placed in the internal iliac before delivery. The balloons can be inflated to occlude the vessels
in the event of postpartum haemorrhage. Embolisation can be performed via the balloon catheters
if bleeding continues despite inflation. Even if hysterectomy is still required, blood loss, blood
transfusion and numbers of admissions to intensive care units can be reduced.


In those with suspected placenta accreta on ultrasound and or risk factors for placenta accreta the
following steps are recommended in preparing for the surgical management of such patients.
These steps are in accordance with published guidelines (RANZCOG and RCOG).

W&CH/GL/M/0002                               Page 3 of 5                       Created: February 2008
Protocol Development: Dr Dianne Poad, CD Obstetrics
Canterbury DHB                                                           Women’s & Children’s Health


1.    Review the films with the radiologist, confirming the site of the placenta, the site of the
      suspected myometrial defect and if it is possible to ascertain if there is bladder involvement.
2.    Counsel the woman and her family about the suspected diagnosis, the need for operative
      delivery if placenta praevia, the implications in terms of massive blood loss, and possible
3.    RANZCOG encourage consent for hysterectomy of it is at all a possibility.
4.    Book the elective caesarean section at a gestation in order to try and avoid labour and an
      emergency procedure. If less than 39 weeks gestation a course of IM betamethasone is
      recommended to reduce fetal respiratory morbidity (ASTECS).
5.    Ideally book the caesarean section at a time when there are no other elective caesareans
      scheduled and make it clear with the charge midwife and booking clerk no others should
      subsequently be booked. This should leave at least one theatre in birthing suite free for
      acute work at all times. If necessary discuss performing the case in the Gynae operating
6.    Arrange dedicated anaesthetic staff if possible in order to prevent emergency cases delaying
      access for surgery.
7.    Inform the charge midwife of the potential of complications related to this caesarean
      section as more core midwives may need to be rostered for that shift.
8.    An anaesthetic consultation is required, including the specific anaesthetic consultant
      rostered to the labour ward that day.
9.    Liaise with the anaesthetist regarding the number of units and blood they require to be
      crossmatched preoperatively.
10.   Consider Urology input if the bladder is thought to be involved, or ureteric stenting may be
11.   Book DSA and discuss with the on call interventional radiologist if uterine artery balloons
      are required preoperatively. They will place the balloons on the day of surgery and can do
      so in labour ward theatres.
12.   If uterine artery balloons are to be used, the operating table in theatre 27 or 26 will need to
      be replaced by one from 24 or 21 so the Image Intensifier can obtain images of the pelvic
13.   Inform Nurse in Charge - Theatres of the case, so she can arrange the change of operating
      table and make sure that she has an experienced scrub nurse and possibly two scrub nurses
14.   Liaise with the neonatal unit for cots.
15. Consider prior warning of the on call haematologist
16.   Liaise with ICU if it is possible a bed may be required postoperatively.
17.   The procedure should be performed by an experienced senior obstetrician and a second
      obstetrician, with the Gynae Oncologist aware if their help may be required.

W&CH/GL/M/0002                               Page 4 of 5                         Created: February 2008
Protocol Development: Dr Dianne Poad, CD Obstetrics
Canterbury DHB                                                          Women’s & Children’s Health

                                 MASSIVE HAEMORRHAGE

Massive haemorrhage should be dealt with in accordance with the recommendations as for
Primary Post Partum Haemorrhage GLM0012.

Uterotonic agents may help in reducing the blood loss associated with bleeding from the
relatively atonic lower uterine segment, while bimanual compression, hydrostatic balloon
catheterization, or uterine packing, or even aortic compression, all of which can buy time while
additional help arrives. Additional surgical manoeuvres which may be considered include the B-
Lynch suture, uterine or internal iliac artery ligation, or hysterectomy. Arterial embolisation has
been reported and is useful in selected cases.

                                BIBLIOGRAPHIC SOURCE(S)

•    Royal College of Obstetricians and Gynaecologists (RCOG). Placenta praevia and placenta
     praevia accreta: diagnosis and management. London (UK): Royal College of Obstetricians
     and Gynaecologists (RCOG); 2005 Oct. 12 p. (Guideline; no. 27).
•    E-MEDICINE - Author: Saju Joy, MD, Fellow, Division of Maternal Fetal Medicine,
     Department of Obstetrics and Gynaecology, The Ohio State University School of Medicine
•    RANZCOG College Statement C-Obs 20, Nov 2005
•    Bhide (2004 Curr Opin Obstet Gynacol 16:447 – 51
•    Sakorn (2007) Am Fam Physician 75 :1199 - 206
•    Up-To-Date 2007

W&CH/GL/M/0002                               Page 5 of 5                     Created: February 2008
Protocol Development: Dr Dianne Poad, CD Obstetrics

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