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Source: deseretnews.com

• Vasa praevia occurs when one or more of the baby's placental or umbilical blood vessels cross the entrance to the birth canal beneath the baby.

• When the cervix dilates or the membranes rupture, the unprotected vessels can tear, causing rapid fetal haemorrhage.

• When the baby drops into the pelvis, the vessels can be compressed, compromising the baby's blood supply and causing oxygen deprivation.

• For a moving video image of vasa praevia diagnosed by colour Doppler, please click on the image below.

Courtesy of thefetus.net

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• It is thought that vasa praevia occurs in approximately 1:2,500 births.

• If the condition is not diagnosed prenatally, the fetal mortality rate is estimated to be as high as 95%.

• In cases diagnosed prenatally (absent other congenital defect) the infant survival rate is 100%.

• VASA PRAEVIA Raising Awareness are not aware of any prenatally diagnosed case which has resulted in the loss of the infant.

• NB. In IVF pregnancies the frequency is 1:300

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• Vasa praevia may present itself with the sudden onset of painless vaginal bleeding in the second or third trimester of pregnancy.

• Vasa praevia may also occur without symptoms, so look for women who fall into the risk groups below.

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•  Those with painless bleeding (at any stage in pregnancy)

•  Those with low-lying placenta or placenta praevia

•  Those with bi-lobed or succenturiate-lobed placenta

Bilobed (succenturiate) Placenta

Courtesy of the www.theFetus.net © Francois Manson

•  Those with velamentous insertion of the cord

Velamentous Cord Insertion

Courtesy and ©of www.ivpf.org

•  In-vitro fertilization pregnancies

•  Multiple pregnancies

•  History of previous uterine surgery including D&C or c-section

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• Diagnosis is made by ultrasound using colour Doppler

• During any anomaly scan the position of the placenta and the placental insertion of the umbilical cord should be recorded (i.e. whether the cord is centrally inserted, marginally inserted, a velamentous insertion or vasa praevia etc.).

• In all cases where the placenta is low lying and/or the where the insertion of the umbilical cord is not central these cases must be referred for further diagnostic testing.

• Additionally, all women presenting with warning signs or within the risk groups above should be scanned using transvaginal colour Doppler ultrasound again to specifically locate the placental-umbilical cord connection (see algorithm below).

• If you suspect vasa praevia and you are not proficient in the use of colour Doppler ultrasound you should refer the patient to someone suitably qualified to make the diagnosis (see what next).

• Recent studies have shown that when vasa praevia is prenatally diagnosed, and a proper management plan is followed, the infant survival rate (absent any other congenital defect) is 100%.

• The Royal College of Obstetricians and Gynaecologists have recently announced that they will be amending the current guidelines on the diagnosis and management of placenta praevia and placenta praevia accreta to specifically include advice on the diagnosis and recommendations of vasa praevia.

• The following diagnostic algorithm was proposed by Philippe Jeanty MD. PhD, to the Fetal Medicine Foundation 6th World Congress in Fetal Medicine (June 2007):

Diagnostic Algorithm for the diagnosis of Vasa Praevia courtesy and © 2007 of www.thefetus.net

[NB. In a study soon to be published over 93% of all clinicians surveyed at the FMF 6^th World Congress indicated that they would adopt this algorithm as a routine practice].

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• Colour Doppler ultrasound is used to measure the velocity of blood flow.

Vasa Praevia confirmed by colour Doppler ultrasound (note the fetal pulse at 150 bpm) - (courtesy and © 2007 of www.thefetus.net)

• Colour Doppler ultrasound can be used to listen to the fetal heartbeat, examine the fetal heart for defects, and estimate placental blood flow.

• During this special type of ultrasound, distinct colours show the different rates of blood flow.

• The colours show the location of fetal vessels thereby eliminating or confirming the diagnosis of vasa praevia.

• To eliminate false positive results for vasa praevia which may be caused by flash artifact sonographers should spend a little more time to make sure it persists. Alternatively, drop a pulse wave sample on the suspicious 'flow' to check that although it has colour it does not have the pulsations that a fetal vessel would. For a more detailed account of pitfalls and how to avoid them please download this educational presentation.

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• Until there is a recognised clinical protocol for the diagnosis of vasa praevia, the minimum standard expected in obstetric care should be the referral of a patient presenting with warning signs or symptoms, or a patient falling within the known risk groups, to a suitably qualified sonographer for a transvaginal ultrasound using colour Doppler.

• If you live in the South or South-East and there is no one within your NHS trust competent to undertake this diagnosis, VASA PRAEVIA Raising Awareness recommends referral to Professor Kypros Nicolaides, c/o The Fetal Medicine Centre.

• If you live in the North or the Midlands, VASA PRAEVIA Raising Awareness recommends referral to Mr Chris Griffin, consultant obstetrician, c/o Midland Ultrasound and Medical Services (mums.me.uk).

• VASA PRAEVIA Raising Awareness was set up with the specific purpose of raising awareness about this condition and to bring about the implementation of a nationally recognised clinical protocol for the antenatal diagnosis and management of vasa praevia.

• Unless something is done, every year up to 400 otherwise normal healthy infants are at risk of death and/or severe physical and mental compromise.

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