SOGC CLINICAL PRACTICE GUIDELINE
Guidelines for the Management of Vasa Previa

https://doi.org/10.1016/S1701-2163(16)34282-7Get rights and content

Abstract

Objectives

To describe the etiology of vasa previa and the risk factors and associated condition, to identify the various clinical presentations of vasa previa, to describe the ultrasound tools used in its diagnosis, and to describe the management of vasa previa.

Outcomes

Reduction of perinatal mortality, short-term neonatal morbidity, long-term infant morbidity, and short-term and long-term maternal morbidity and mortality.

Evidence

Published literature on randomized trials, prospective cohort studies, and selected retrospective cohort studies was retrieved through searches of PubMed or Medline, CINAHL, and the Cochrane Library, using appropriate controlled vocabulary (e.g., selected epidemiological studies comparing delivery by Caesarean section with vaginal delivery; studies comparing outcomes when vasa previa is diagnosed antenatally vs. intrapartum) and key words (e.g., vasa previa). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. Searches were updated on a regular basis and incorporated into the guideline to October 1, 2008. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and from national and international medical specialty societies.

Values

The evidence collected was reviewed by the Diagnostic Imaging Committee and the Maternal Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on Preventive Health Care.

Benefits, Harms, and Costs

The benefit expected from this guideline is facilitation of optimal and uniform care for pregnancies complicated by vasa previa.

Sponsors

The Society of Obstetricians and Gynaecologists of Canada.

Summary Statement

A comparison of women who were diagnosed antenatally and those who were not shows respective neonatal survival rates of 97% and 44%, and neonatal blood transfusion rates of 3.4% and 58.5%, respectively. Vasa previa can be diagnosed antenatally, using combined abdominal and transvaginal ultrasound and colour flow mapping; however, many cases are not diagnosed, and not making such a diagnosis is still acceptable. Even under the best circumstances the false positive rate is extremely low. (II-2)

Recommendations

  • 1.

    If the placenta is found to be low lying at the routine second trimester ultrasound examination, further evaluation for placental cord insertion should be performed. (II-2B)

  • 2.

    Transvaginal ultrasound may be considered for all women at high risk for vasa previa, including those with low or velamentous insertion of the cord, bilobate or succenturiate placenta, or for those having vaginal bleeding, in order to evaluate the internal cervical os. (II-2B)

  • 3.

    If vasa previa is suspected, transvaginal ultrasound colour Doppler may be used to facilitate the diagnosis. Even with the use of transvaginal ultrasound colour Doppler, vasa previa may be missed. (II-2B)

  • 4.

    When vasa previa is diagnosed antenatally, an elective Caesarean section should be offered prior to the onset of labour. (II-1A)

  • 5.

    In cases of vasa previa, premature delivery is most likely; therefore, consideration should be given to administration of corticosteroids at 28 to 32 weeks to promote fetal lung maturation and to hospitalization at about 30 to 32 weeks. (II-2B)

  • 6.

    In a woman with an antenatal diagnosis of vasa previa, when there has been bleeding or premature rupture of membranes, the woman should be offered delivery in a birthing unit with continuous electronic fetal heart rate monitoring and, if time permits, a rapid biochemical test for fetal hemoglobin, to be done as soon as possible; if any of the above tests are abnormal, an urgent Caesarean section should be performed. (III-B)

  • 7.

    Women admitted with diagnosed vasa previa should ideally be transferred for delivery in a tertiary facility where a pediatrician and blood for neonatal transfusion are immediately available in case aggressive resuscitation of the neonate is necessary. (II-3B)

  • 8.

    Women admitted to a tertiary care unit with a diagnosis of vasa previa should have this diagnosis clearly identified on the chart, and all health care providers should be made aware of the potential need for immediate delivery by Caesarean section if vaginal bleeding occurs. (III-B)

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      Postnatal diagnosis can be made at delivery by macroscopic examination showing ruptured vessels running freely through the membranes and absence of insertion of the umbilical cord on the placenta, but on the membranes, more than two centimeters from the placental edge. As the occurrence of spontaneous rupture of membranes cannot be predicted, the Society of Obstetricians and Gynaecologists of Canada recommends that, if diagnosed early, antenatal corticosteroid therapy should be given at 28–32 weeks of amenorrhea, and that patients should be admitted to a level 3 maternity from 30 to 32 weeks of amenorrhea, but does not give an ideal term for a scheduled caesarean section [16]. Indeed, the term at which it should be performed is still debated and there are no studies with a sufficient level of evidence to answer this question.

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      All women with placenta previa or low-lying placenta have an increased risk of a morbidly adherent placenta (placenta accreta spectrum disorders), particularly those with a prior cesarean delivery.11,23 Further, all women with a placenta previa or low-lying placenta have an increased risk of vasa previa, particularly those with a marginal/velamentous cord insertion close to the cervical os or a succenturiate placental lobe.10,14,24 These conditions carry significant implications for maternal-fetal outcomes and need to be further assessed or ruled out.

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      A guideline recommends that hospitalisation at approximately 30–32 weeks and the administration of corticosteroids to promote foetal lung maturation be considered in affected patients [48]. Conversely, it has also been reported that in selected asymptomatic patients, outpatient management is also a possible option [48,49]. Nevertheless, precise outpatient investigations, including confirmation of the presence of uterine contractions and condition of the uterine cervix and FHR, should be provided in pregnant patients with vasa praevia.

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    • Can we perform a prenatal diagnosis of vasa previa to improve its obstetrical and neonatal outcomes?

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      Moreover, the lack of systematic anatomo-pathological examination of the placenta after delivery may have contributed to this undervaluation. Prenatal sonographic diagnosis of VP and elective cesarean delivery before rupture of the membranes, labor or significant bleeding are associated with excellent survival rates (reported to be 97–99%), while cases undiagnosed antenatally are subject to a disastrous outcome (fetal mortality rate is reported to be 44–100%) [1–8]. Furthermore, the antenatal identification of VP avoids us the need for blood transfusion for both fetus and mothers in all cases.

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    This guideline has been prepared by the Diagnostic Imaging Committee and the Maternal Fetal Medicine Committee and approved by Executive and Council of the Society of Obstetricians and Gynaecologists of Canada.

    Disclosure statements have been received from all members of the committees.

    This document reflects emerging clinical and scientific advances on the date issued and is subject to change. The information should not be construed as dictating an exclusive course of treatment or procedure to be followed. Local institutions can dictate amendments to these opinions. They should be well documented if modified at the local level. None of these contents may be reproduced in any form without prior written permission of the SOGC.

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