Placenta Praevia

Last updated 20.09.12

Definition

-  Placenta inserted wholly or partly into lower segment of uterus in third trimester (>27/40) of pregnancy

-  Major (complete): placenta over cervical os

-  Minor (marginal): lower segment not including cervical os

-  Low Lying: placenta near or over os prior to third trimester

 

Locations

 

Features

-  Usually detected in routine morphology scan at 18/40 (low lying)

-  Incidence

-  5% pregnancies 16-18/40 = low lying

-  0.5% at term = placenta praevia

-  Mortality rate 1% developed world

-  Neonatal mortality & morbidity related to preterm delivery

-  Maternal mortality 0.03%

 

Location

 

Risk Factors

-  Previous uterine surgery

-  0.9% x1 prev LUSCS

-  1.7% x2 prev LUSCS

-  3.0% x3 prev LUSCS

-  D&C, myomectomy, hysterotomy

-  Multiple gestation: twins..

-  Increasing parity

-  Increasing materal age

-  Male fetus

 

Associated S/S

-  Vaginal bleeding: APH, intrapartum haemorrhage

-  +/- Painless

-  70% pts 1+ episodes

-  30% pts prior to 30/40

-  30% btwn 30-36/40

-  10% pts reach term wo bleeding

-  More common in third trimester (expanding lower segment)

-  Contractions 10-20%

-  Abnormal lie or high head (suspicious for)

 

Complications

-  IUGR (abnormal placentation & vascularisation)

-  PPROM (impaired integrity of membranes)

-  Malpresentation: breech

-  Recurrence 4-8%

-  Placenta accreta 1-5% praevias

-  Increased risk if previous LUSCS

-  Higher risk of need for hysterectomy at LUSCS

-  Vasa praevia

-  +/- vilamentous cord insertion

 

Ix

-  US: transvaginal

-  Second trimester 18-20/40 morphology scan: low lying

-  Third trimester: placenta praevia

-  Exlcude vasa praevia & placenta accreta

-  Due to angle of probe to cervical canal TV probe is safe to use

-  Should document how many mm from os

-  +/- as per APH

 

Mx

-  Low lying placenta on morphology scan needs F/U in third trimester US

-  Acute Mx

-  Obstetric emergency: APH

-  Admission

-  Maternal vitals

-  CTG

-  No tocolysis: relaxes uterus & promoted ongoing bleeding

-  Emergency LUSCS if

-  Fetal viability

-  Abnormal CTG unresponsive to O2, position & fluids

-  Life threatening haemorrhage

-  Significant PV bleeding >34/40

-  D/C home

-  Once 48hrs asymptomatic (no bleeding)

-  Live within 20min of hospital

-  Adult companion available 24hrs for immediate transport

-  Reliable patient

-  Able to maintain bed rest at home

-  Pt understands risk of out-pt management

-  >20/40

-  Third trimester US

-  Minor praevia & asymptomatic: 32-36/40

-  Major praevia & asymptomatic: 30-32/40

-  If symptomatic case by case Mx

-  +/- cervical length

-  Avoidance of intercourse & VE

-  Immediate medical R/V if vaginal bleeding

-  Plan delivery

-  If minor praevia & >20mm from os consider trial of labour

-  Book elective LUSCS for

-   All major praevias at 37-38/40 (avoid presenting in labour)

-   Minor praevia at 39/40

-   Prepare for major bleed

-   If possibility of accreta LUSCS in tertiary hospital (+/- hysterectomy)

 

 

 

References

 

UpToDate: Management of Placenta Previa, Lockwood et al, 28/11/11

UpToDate: Clinical Manifestations & Diagnosis of Placenta Previa, Lockwood et al, 08/02/2011

3 Centres Collaboration: Antepartum Haemorrhage (APH), Including Placenta Praevia, Abruption and Vasa Praevia, 21/12/11

eMedicine: Placenta Previa in Emergency Medicine, Ko et al, 04/04/2011

Pic (praevia): www.babycenter.com.au/pregnancy/complications/placentapraevia/