Vasa Previa

Fetal mortality 50 to 60%

• First reported in 1801
• Considered an inevitable undetectable tragedy for over 185 years
• First ultrasound description in 1987
• Prenatal diagnosis made with visualization of fetal vessels passing across or within 2 cm of the internal cervical os.

• Reported incidence 1 per 2500 pregnancies
• Appears to be increasing
• May be as high as 1 per 350 pregnancies
• May be more common than Down syndrome

Type 1

Type 2

AIUM Guidelines

UK OB Survey

• 20% wouldn't recommend cesarean for vasa previa
• 30% couldn't name one risk factor for vasa previa
• 40% didn't know how to identify a vasa previa

http://www.aium.org/resources/guidelines/obstetric.pdf

“The placental location, appearance, and relationship to the internal cervical os should be documented. The umbilical cord should be imaged and the number of vessels in the cord documented. The placental cord insertion site should be documented when technically possible. A velamentous (also called membranous) placental cord insertion that crosses the internal os of the cervix is vasa previa, a condition that has a high risk of fetal mortality if not diagnosed before labor.”

Prenatal Diagnosis

Risk Factors

• Velamentous cord insertion
• Resolving placenta previa
• IVF pregnancy
• Multiple gestations
• Extra-placental mass (succenturiate lobe)

Ultrasound Guidelines

• Image cord insertion
• Rule out placenta previa

Cipriano, L E, W H Barth, and G S Zaric. 2010. The cost-effectiveness of targeted or universal screening for vasa praevia at 18-20 weeks of gestation in ontario. BJOG 117 (9): 1108-18.

Ioannou, C and C Wayne. 2010. Diagnosis and management of vasa previa: A questionnaire survey. Ultrasound Obstet Gynecol 35 (2): 205-9.

Oyelese, Yinka, Val Catanzarite, Federico Prefumo, Susan Lashley, Morey Schachter, Yosi Tovbin, Victoria Goldstein, and John C Smulian. 2004. Vasa previa: The impact of prenatal diagnosis on outcomes. Obstet Gynecol 103 (5 Pt 1): 937-42.

Oyelese, Yinka and John C Smulian. 2006. Placenta previa, placenta accreta, and vasa previa. Obstet Gynecol 107 (4): 927-41.

Rebarber, Andrei, Cara Dolin, Nathan S Fox, Chad K Klauser, Daniel H Saltzman, and Ashley S Roman. 2014. Natural history of vasa previa across gestation using a screening protocol. J Ultrasound Med 33 (1): 141-7.

Velamentous Insertion

• Prenatal diagnosis saves lives
• Fetal mortality rate 50 to 60% if pregnancy progresses past 36 weeks
• Delivery by cesarean at 35 weeks' gestation reduces fetal death rate to near zero

Found in 70% of vasa previa cases

Internal Cervical Os

• Vasa previa screening: transvaginal ultrasound with color Doppler
• Universial screening not cost effective
• Screen for the five risk factors found to be cost effective
• Velamentous cord insertion
• Resolving placenta previa
• IVF
• Multiple gestations
• Succenturiate placenta

Once a vasa previa, always a vasa preva?

• A vasa previa detected in the 2nd trimester may "resolve" by the 3rd trimester.
• When the diagnosis is made before 26 weeks’ gestation, 1 in 4 will resolve by 30 weeks’ gestation.
• This may actually represent false postive diagnosis in the second trimester

Resolving Placenta Previa

Coronal

Longitudinal

Vasa Previa

Additional Risk Factors

• IVF pregnancy 10%
• Multiple gestation 5%
• Succenturiate placenta 30%