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Vasa Praevia: Diagnosis and Management (GTG 27B - Sep 2018) - Coggle…
Vasa Praevia: Diagnosis and Management
(GTG 27B - Sep 2018)
Epidemiology
Type I
: Vessel is connected to a velamentous umbilical cord
Type II
: Vessel connects the placenta with a succenturiate or accessory lobe
Defintion
: Occurs when the fetal vessels run through the free placental membranes within 2cm of the cervix, unprotected by placental tissue or Wharton's jelly of the umbilical cord
Prevalence
: Between
1/1200 and 1/5000
Ultrasound definition
: Within 2cm from the internal cervical os
Up to 80% of cases
have 1 or more identifiable prenatal risk factors
Risks
Vessel rupture during labour and delivery
: Rupture in active labour or when ARM is performed, in particular when located near or over the cervix, under the fetal presenting part
Total fetal blood volume at term: 80-100ml/kg
A relatively small amount of blood loss can have major implications and is rapidly fatal to the fetus.
Preterm delivery and associated complications
Diagnosis
Vaginal examination
: Usually during early labour, detecting pulsating fetal vessels inside the internal os
Dark red-vaginal bleeding
and acute fetal compromise after SROM or ARM (
fetal mortality rate at least 60%
)
Classic presentation of unexpected vasa praevia in labour
: Presence of painless vaginal bleeding (
Benckiser's haemorrhage
), occurring mainly when the cervix is effaced and dilated, and there is SROM or ARM.
Vasa praevia diagnosed in the 2nd trimester resolves in around
20% of cases before delivery
. Advise follow-up ultrasound at 32 weeks, particularly in women with low-lying placenta as this is still associated with high risk of vasa praevia.
Investigations
Ultrasound
: Diagnosing vasa praevia at the time of the routine fetal anomaly scan has
high diagnostic accuracy
and
low false-positive rate
. Combination of both transabdominal and transvaginal
colour Doppler ultrasound
provides the best diagnostic accuracy.
97% survival rate in cases of prenatal diagnosis
compared to 44% when diagnosis made during delivery
Prenatal diagnosis
:
Most effective around
midpregnancy (18-24 weeks)
, but needs to be confirmed in the
3rd trimester (30-32 weeks)
Document
placental cord insertion
when technically possible at the routine fetal anomaly scan
Risk Factors
Placenta anomalies: Placenta praevia, bilobed placenta, succenturiate placental lobes
Assisted reproductive techniques
Velamentous cord insertion
Management
Do not delay delivery
while trying to confirm diagnosis, especially if there is fetal compromise, due to speed at which fetal exsanguination can occur and high perinatal mortality rate associated with ruptured vasa praevia
Elective Caesarean section
: Ideally carried out prior to onset of labour if vasa praevia confirmed in 3rd trimester
Prophylactic hospitalisation from 30-32 weeks: Individualised decision based on combination of factors including multiple pregnancy, antenatal bleeding, and threatened premature labour
PPROM/preterm labour
: Perform a Caesarean section without delay
Delivery
: Aim is to deliver before rupture of membranes while minimising impact of iatrogenic prematurity. Plan C/S at
34-36 weeks
in asymptomatic women.
Corticosteroids
: Recommend from 32 weeks due to increased risk of preterm delivery