The RCOG today publishes its third edition of the Green-top Guideline on diagnosing and managing placenta praevia, placenta praevia accreta and for the first time vasa praevia.
The new guideline addresses screening, diagnosis and clinical management.
Placenta praevia is a complication of pregnancy where the placenta is inserted wholly or in part into the lower segment of the uterus and may cover all or part of the opening to the neck of the womb (cervix). Placenta praevia accreta is where the placenta is morbidly adherent. The placenta attaches itself deeply into the myometrium (muscle layer of the uterine wall) and can penetrate through completely.
Maternal and fetal morbidity and mortality from placenta praevia and placenta praevia accreta are considerable. With the increase in the number of cases of caesarean section and rising maternal age, the problem of placenta praevia and its complications, including placenta accreta, will become more common.
The guidelines state that clinical suspicion of placenta praevia should be raised in all women with vaginal bleeding after 20 weeks of gestation and that the routine antenatal screening ultrasound scan at 20 weeks offered to all pregnant women, should include placental localisation.
Vasa praevia is where fetal blood vessels from the umbilical cord course through the membranes in the lower part of the uterus over the cervical opening. The blood vessels are unprotected by the placenta or umbilical cord. When the membranes rupture (waters break) in labour, the unprotected blood vessels may rupture resulting in fetal haemorrhage. Vasa praevia, therefore, often presents as an emergency with fresh red vaginal bleeding at the time of membrane rupture with abnormal heart rate patterns on fetal monitoring. The mortality rate in this situation is around 60%. It is the baby at risk and vasa praevia is not a risk to the mother’s life.
Vasa praevia is rare, occurring between 1 in 2000 and 1 in 6000 pregnancies, however the risk factors include placenta praevia, a bilobed placenta or a succenturiate lobe (the unprotected fetal blood vessels course through the membranes between the separate lobes of the placenta), multiple pregnancy and in vitro fertilization.
In addition, it is difficult to diagnose. In the antenatal period, in the absence of vaginal bleeding, there is no method to diagnose it by manual clinical examination. In labour, once the cervix has started to dilate, the blood vessels may be felt on vaginal examination. In the emergency situation where there is vaginal bleeding with membrane rupture and fetal distress, delivery should be by urgent caesarean section without attempting to diagnose vasa praevia. Where vasa praevia is suspected antenatally, abdominal combined with vaginal scanning with colour Doppler ultrasound scan may assist in the diagnosis of vasa praevia but is not 100% accurate.
The UK National screening committee does not recommend routine ultrasound screening for placenta praevia or vasa praevia but supports the current local practices of identifying women whose placenta encroaches on the cervical opening at the routine 20-week antenatal ultrasound scan.
For more information please contact Naomi Weston on 020 7772 6357 or firstname.lastname@example.org
To read the full guideline please click here.