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Vasa Previa

32 F with Vaginal Bleeding • Xray of the Week

Patient at 25 weeks gestational age.

Figure 1. Sagittal transvaginal ultrasound of the cervix.

Figure 2. Sagittal transvaginal ultrasound of the cervix.

A. Gray scale images show the fetal umbilical cord blood vessels (red arrow) across or near the internal os (orange arrow).

B. Color doppler images show the fetal umbilical cord vessels across or near the internal os (yellow arrow).

Discussion:

Vasa previa is a rare and serious complication of pregnancy in which fetal umbilical cord blood vessels run across or near the internal opening of the cervix (1). Because the vessels run within the membranes, they are unsupported by the umbilical cord, placental tissue, or Wharton jelly (1). This increases risk of vessel rupture when the membranes rupture during labor. There are two types of vasa previa. In type I, there is a velamentous cord insertion between the umbilical cord and the placenta (2). Thus the fetal vessels that run freely within the amniotic membranes run across the cervix or near it (Figs. 1, 2) (2) In type II, fetal vessels run between lobes of succenturiate or bilobate placentas over or near the cervix (1,2). There are several methods used to diagnose vasa previa including identification of placental cord insertion, applying color Doppler over the cervix, 3D ultrasound, and transvaginal ultrasound (3). Linear echolucent structures can be seen over the cervix on gray-scale US (Fig. 2A) (4). These linear echolucent structures can also be seen in marginal sinus previa, which appears as a discontinuous venous lake at the placental margin (1,4). Pulsed Doppler will show a fetal umbilical or venous waveform in vasa previa whereas marginal sinus previa present with flow of a maternal heart frequency (1). Color doppler sonography shows vascular structures over the internal cervical os with a “fixed position during maternal repositioning” (Fig. 2B) (4).Funic presentation (also known as cord presentation) is also commonly confused for vasa previa, but they are different in that the funic presentation demonstrates shifting in position of the cord by tapping the transducer (1). Rupture of the fetal blood vessels can be fatal in vasa previa, so it typically requires elective C-section at 35 weeks (1). Hospitalization with corticosteroids at 32 weeks has also been recommended to promote lung maturity (1).

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References:

1. Derbala Y, Grochal F, Jeanty P. Vasa previa. J Prenat Med. 2007;1(1):2-13. 2. Sinkey RG, Odibo AO, Dashe JS. #37: Diagnosis and management of vasa previa. American Journal of Obstetrics & Gynecology. 2015;213(5):615-619. doi:10.1016/j.ajog.2015.08.031 3. Marr S, Ashton L, Stemm A, Cincotta R, Chua J, Duncombe G. Vasa praevia: ultrasound diagnosis at the mid‐trimester scan. Australas J Ultrasound Med. 2013;16(1):8-15. doi:10.1002/j.2205-0140.2013.tb00091.x 4. Fadl S, Moshiri M, Fligner CL, Katz DS, Dighe M. Placental imaging: normal appearance with review of pathologic findings. RadioGraphics. 2017;37(3):979-998. doi:10.1148/rg.2017160155

Amara Ahmed is a medical student at the Florida State University College of Medicine. She serves on the executive board of the American Medical Women’s Association and Humanities and Medicine. She is also an editor of HEAL: Humanism Evolving through Arts and Literature, a creative arts journal at the medical school. Prior to attending medical school, she graduated summa cum laude from the Honors Medical Scholars program at Florida State University where she completed her undergraduate studies in exercise physiology, biology, and chemistry. In her free time, she enjoys reading, writing, and spending time with family and friends.

Follow Amara Ahmed on Twitter @Amara_S98

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Kevin M. Rice, MD is the president of Global Radiology CME

Dr. Rice is a radiologist with Renaissance Imaging Medical Associates and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

Follow Dr. Rice on Twitter @KevinRiceMD

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