Vasa Previa Fact Sheet

Cause

Vasa previa occurs when fetal blood vessel(s) from the placenta or umbilical cord cross the entrance to the birth canal, beneath the baby. Vasa previa can result in rapid fetal hemorrhage (occurs from the vessels tearing when the cervix dilates or membranes rupture) or lack of oxygen (if the vessels become pinched off as they are compressed between the baby and the walls of the birth canal). The aberrant vessels result from velamentous insertion of the cord, bilobed or succenturiate lobed placenta.

Symptoms

Vasa previa can be asymptomatic but can also present with sudden onset of abnormally heavy or small amounts of painless vaginal bleeding in the second or third trimester of pregnancy. Source of blood should always be investigated to determine whether the blood is maternal or fetal if the baby is not in distress.

Incidence

Rarely reported, occurs in 1:2500 births with a fetal mortality rate estimated to be as high as 95 percent if not diagnosed prenatally. ^(1-2)

Prognosis

When properly diagnosed prenatally, prognosis of survival is very good. The fetal mortality rate is very low when an elective C-section is performed after fetal lung maturity is adequate.

Antepartum Diagnosis

Changing current routine obstetrical ultrasound protocols to include visualizing the placental cord connection for velamentous cord insertion during all routine obstetrical ultrasounds is recommended (preferably with color Doppler). All suspected cases of velamentous cord insertion, placenta previa, low-lying placenta, multi-gestational pregnancies, and multi-lobed placentas need to be checked for vasa previa with transvaginal color Doppler ultrasound. ⁽³⁾ Vasa previa can be detected during pregnancy with use of transvaginal sonography in combination with color Doppler. ⁽⁴⁾ Infant death from vasa previa is preventable if diagnosed prenatally.

Warning Signs

Vasa previa might be present if any of the following conditions exist: low-lying placenta (may be caused by previous miscarriages followed by curreting of the uterus (D&C) or uterine surgeries, which can cause scarring in the uterus), bilobed or succenturiate-lobed placentas, velamentous insertion of the cord, pregnancies resulting from in-vitro fertilization or multiple pregnancies. ^(5-6) Vasa previa bleeding is painless. Other obstetrical or birthing bleeding complications are not necessarily painless.

Treatment

When diagnosed prenatally, treatment plans could include the following: use of tocolytes to stop all uterine activity; total pelvic rest including no sexual intercourse or vaginal exams other than transvaginal ultrasound (which has been proven to be safe); hospitalization in the 3rd trimester (usually at about 30-32 weeks); regular ultrasounds to monitor progression of vasa previa; determination of source of bleeding (either fetal or maternal); steroid treatment to develop fetal lung maturity; and most importantly, elective cesarean delivery early enough to avoid an emergency but late enough to avoid complications of prematurity. Current research recommends that 35 weeks may be the optimal time for delivery of vasa previa infants.^{(8, 9)} When not diagnosed prenatally, aggressive resuscitation complete with blood transfusion for the infant if necessary must be planned for and/or expected. ⁽⁷⁾

All cases of vasa previa are different and any management plan should be developed in partnership between the mother and her doctors based on her own individual circumstances. The management recommendations provided by the IVPF are general recommendations only and can be used as the starting point for the development of an individual management plan. The IVPF does not provide medical advice and it is important that if you are diagnosed with vasa previa you consult with an appropriately qualified medical practitioner.

REFERENCES

(1) Vago T. Caspi E. Antepartum bleeding due to injury of velamentous placental vessels. Obstet Gynecol 1962;20:671-5
(2) Quek, SP, Tan KL. Vasa praevia. Aust NZ J Obstet Gynaecol 1972;12:206
(3) Gianopoulos J, Carver T, Tomich P et al. Diagnosis of vasa previa with ultrasonography. Obstet Gynecol 1987;69(3 Pt 2):488-491
(4) Meyer WJ Blumenthal L, Cadkin A et al. Vasa previa: Prenatal diagnosis with transvaginal color Doppler flow imaging. Am J Obstet Gynecol 1993; 169:1627-1629
(5) Evans GM. Vasa praevia. Br Med J 1952;2:1243
(6) McAfee CHG. Placenta praevia-A study of 174 cases. J Obstet Gynaecol Br Emp 1945;52:313
(7) K.O Oyelese, M. Turner, C. Lees and S. Campbell. Vasa Previa: An Avoidable Obstetric Tragedy. Obstet and Gynec Survey 1999; Volume 54, Number 2:138-144
(8) Yinka Oyelese MD, Val Catanzarite MD, Federico Prefumo MD, Susan Lashley MD, Morey Schachter MD, Yosi Tovbin MD, Victoria Goldstein MBA, John C. Smulian MD, MPH. Vasa Previa: The Impact of Prenatal Diagnosis on Outcomes; Obstet Gynecol 2004;103:937-942.
(9) Yinka Oyelese MD, John C. Smulian MD, MPH. Placenta Previa, Placenta Accreta, and Vasa Previa. Obstet Gynecol 2006;107:927-941.