2. Definition
• Rupture of a fetal vessel
• Result of a velamentous insertion of the umbilical cord into the
membranes
–Veins travel across the amniotic membranes before coming
together in umbilical cord
3. Pathophysiology
• This is a situation where blood vessels (or their branches) in the
umbilical cord develop a route away from the cord and placenta
proper and are found just above the cervical opening
• That means they are, in effect, between the baby’s leading part
(usually the head) and the cervical opening
• Once the cervix starts dilating, the delicate vessels will be stretched
and will soon tear.
• This will unleash torrential vaginal bleeding.
4. Risk factors
• A low lying placenta (placenta praevia)
• Multiple pregnancy (twins or more)
• A placenta where the cord insertion is peripheral rather than central
(velamentous insertion of cord)
• IVF pregnancy: For some obscure reason, IVF pregnancy increases the
risk of vasa praevia almost 10-fold to an estimated 1 in 300.
• Previous history of uterine surgery including minor procedures such
as D&C
5. ALTERATIONS IN THE FETAL HEART RATE
• Initial fetal tachycardia—fetus attempts to compensate for acute
blood loss
• Bradycardia
• Intermittent accelerations
Note that;
• Fetal mortality reported to be greater than 50% Hence you must
make diagnosis rapidly and institute definitive therapy and delivery
6. Investigation
APT TEST
Used to detect fetal blood.
• The blood is mixed with a small amount of tap water to cause
hemolysis.
• The sample is next centrifuged for several minutes.
• The pink hemoglobin-containing supernatant is then mixed with 1 mL
of 1% NaOH for each 5 mL of supernatant.
• The color of the fluid is assessed after 2 minutes. Fetal hemoglobin
will stay pink and adult hemoglobin will turn yellow-brown.
7. Management
• Consider hospitalization in the third trimester to provide proximity to
facilities for emergency cesarean delivery.
• Fetal surveillance to detect compression of vessels.
• Antenatal corticosteroids to promote lung maturity.
• Elective cesarean delivery at 35 to 36 weeks of gestation.
• Avoid amniotomy as the risk of fetal mortality is 60-70% with rupture
of the membranes
