Guideline No. 439: Diagnosis and Management of Vasa Previa

Vasa previa guidelines and their supporting evidence

INTRODUCTION

Vasa previa (VP) is a serious pregnancy complication in which fetal vessels, unprotected by the umbilical cord, run across or within close proximity to the internal cervical os, which can potentially result in fetal exsanguination in the event of membrane rupture. There is global consensus that women with antenatally diagnosed VP should have caesarean delivery prior to onset of labour to prevent the catastrophic complications of VP. However, there is variability in the approach to management of these women antenatally, particularly regarding hospitalisation and timing of steroid administration and delivery.

CONTENT

In this review, we aim to compare the VP guidelines of four prominent obstetric advisory bodies: The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG), The Royal College of Obstetricians and Gynaecologists (RCOG), The Society for Maternal-Fetal Medicine (SMFM) and The Society of Obstetricians and Gynaecologists of Canada (SOGC) with a particular focus on antenatal hospitalisation, administration of steroids, and timing of birth in asymptomatic patients. We also aim to evaluate the evidence cited to support their recommendations.

SUMMARY

Current guidelines are based on low-quality evidence that often does not include insights from recent studies and are vague in their recommendations for antenatal hospitalisation and timing of delivery.

OUTLOOK

More robust evidence for management of VP is needed to inform future guidelines.

Fetoscopic Laser Surgery for Vasa Previa: Feasibility, Safety, and Future Directions

Vasa previa is an uncommon, potentially life-threatening condition where fetal vessels traverse the membranes over the cervix without Wharton jelly protection, risking fetal exsanguination if undiagnosed. Prenatal ultrasound and planned preterm cesarean reduce perinatal mortality to under 1%, though concerns about prematurity persist. Fetoscopic laser photocoagulation, initially used for twin-twin transfusion syndrome, shows promise in select cases, potentially allowing vaginal delivery at term. This review examines vasa previa management, the feasibility of laser therapy, and its risks. While early data are promising, further studies, including the FLUMEN trial, are needed to determine the safety and efficacy of this intervention.

Vasa Previa: Prenatal Diagnosis and the Rationale Behind Using a 5 cm Distance from Internal Os

In pregnancies with vasa previa, prenatal diagnosis and pre-labor cesarean delivery are associated with significantly improved perinatal outcomes compared to undetected cases. However, a universally accepted ultrasonographic definition of vasa previa is lacking. Specifically, the distance from the cervical internal os beyond which vaginal delivery can be safely recommended remains to be determined. Field experts and recently published societal guidelines agree that a 2 cm cut-off is suboptimal, given that complete cervical dilation during labor risks unprotected fetal vessels within a 5 cm radius from the internal os. Thus, in the setting of a scarcity of evidence and case reports of perinatal death with unprotected fetal vessels beyond 2 cm from the internal os, a more conservative definition that includes unprotected fetal vessels located within 5 cm of the internal os is imperative to improve outcomes.

A Case of Vasa Previa Diagnosed at Term: Elective Caesarean Section with Good Feto-Maternal Outcomes

Vasa previa is a condition where unprotected fetal vessels, neither by placenta nor umbilical cord, lie within the membranes over the internal cervical ostium and beneath the presenting part of the fetus. Due to this condition, the membranous vessels pose a higher risk of being compressed or ruptures and could lead to fetal demise, exsanguination, or even fetal death. In this case report, we reported a case of a 36-year-old woman, G3P2A0, at term gestation and oblique lie. Early prenatal diagnosis using transvaginal ultrasound could increase the survival rate of the fetus if followed by sufficient management after diagnosis. Caesarean birth is the safest mode of delivery even before the clinical signs or onset of labor occur.

Vasa previa in singleton pregnancies: diagnosis and clinical management based on an international expert consensus

BACKGROUND

There are limited data to guide the diagnosis and management of vasa previa. Currently, what is known is largely based on case reports or series and cohort studies.

OBJECTIVE

This study aimed to systematically collect and classify expert opinions and achieve consensus on the diagnosis and clinical management of vasa previa using focus group discussions and a Delphi technique.

STUDY DESIGN

A 4-round focus group discussion and a 3-round Delphi survey of an international panel of experts on vasa previa were conducted. Experts were selected on the basis of their publication record on vasa previa. First, we convened a focus group discussion panel of 20 experts and agreed on which issues were unresolved in the diagnosis and management of vasa previa. A 3-round anonymous electronic survey was then sent to the full expert panel. Survey questions were presented on the diagnosis and management of vasa previa, which the experts were asked to rate on a 5-point Likert scale (from "strongly disagree"=1 to "strongly agree"=5). Consensus was defined as a median score of 5. Following responses to each round, any statements that had median scores of ≤3 were deemed to have had no consensus and were excluded. Statements with a median score of 4 were revised and re-presented to the experts in the next round. Consensus and nonconsensus statements were then aggregated.

RESULTS

A total of 68 international experts were invited to participate in the study, of which 57 participated. Experts were from 13 countries on 5 continents and have contributed to >80% of published cohort studies on vasa previa, as well as national and international society guidelines. Completion rates were 84%, 93%, and 91% for the first, second, and third rounds, respectively, and 71% completed all 3 rounds. The panel reached a consensus on 26 statements regarding the diagnosis and key points of management of vasa previa, including the following: (1) although there is no agreement on the distance between the fetal vessels and the cervical internal os to define vasa previa, the definition should not be limited to a 2-cm distance; (2) all pregnancies should be screened for vasa previa with routine examination for placental cord insertion and a color Doppler sweep of the region over the cervix at the second-trimester anatomy scan; (3) when a low-lying placenta or placenta previa is found in the second trimester, a transvaginal ultrasound with Doppler should be performed at approximately 32 weeks to rule out vasa previa; (4) outpatient management of asymptomatic patients without risk factors for preterm birth is reasonable; (5) asymptomatic patients with vasa previa should be delivered by scheduled cesarean delivery between 35 and 37 weeks of gestation; and (6) there was no agreement on routine hospitalization, avoidance of intercourse, or use of 3-dimensional ultrasound for diagnosis of vasa previa.

CONCLUSION

Through focus group discussion and a Delphi process, an international expert panel reached consensus on the definition, screening, clinical management, and timing of delivery in vasa previa, which could inform the development of new clinical guidelines.

Fetoscopic laser photocoagulation: a medically reasonable treatment option in the management of types II and III vasa previa

Vasa previa is a condition where unprotected fetal vessels cross the cervix within the membranes, posing a considerable risk of fetal death or severe morbidity if the membranes rupture before or during delivery. There has not been a definitive in utero treatment for this condition. Patients are typically closely monitored and hospitalized in the early third trimester and scheduled for cesarean delivery before term. This approach poses considerable physical, social, psychological, and financial challenges for pregnant patients and their families. Furthermore, fetal vessel rupture may lead to severe hypoxic-ischemic injury and consequent neurodevelopmental impairment. Finally, babies delivered early due to vasa previa may face both the short- and long-term consequences of prematurity. Recently, fetoscopic laser photocoagulation using a single-port fetoscope has emerged as a potential therapeutic option for patients with types II and III vasa previa. This innovative approach aims to reduce hospital stays, increases the chance of successful vaginal delivery, and potentially allows pregnancies to reach full term, providing lifelong benefits for the infant. Preliminary clinical studies on human subjects have demonstrated promising results concerning the feasibility, safety, and efficacy of this intervention for a subset of patients with types II and III vasa previa. After reviewing the current state of the art, we argued that offering fetoscopic laser photocoagulation in specialized centers under IRB supervision meets the ethical obligations of beneficence and non-maleficence for both pregnant and fetal patients, as well as the autonomy-based obligations for pregnant patients.

Antenatal reproductive screening for pregnant people including preconception: Provides the best reproductive opportunity for informed consent, quality, and safety

INTRODUCTION

This antenatal screening review will include reproductive screening evidence and approaches for pre-conception and post-conception, using first to third trimester screening opportunities.

METHODS

Focused antenatal screening peer-reviewed publications were evaluated and summarized.

RESULTS

Evidenced-based reproductive antenatal screening elements should be offered and discussed, with the pregnancy planning or pregnant person, during Preconception (genetic carrier screening for reproductive partners, personal and family (including reproductive partner) history review for increased genetic and pregnancy morbidity risks); First Trimester (fetal dating with ultrasound; fetal aneuploidy screening plus consideration for expanded fetal morbidity criteria, if appropriate; pregnant person preeclampsia screening; early fetal anatomy screening; early fetal cardiac screening); Second Trimester for standard fetal anatomy screening (18-22 weeks) including cardiac; pregnant person placental and cord pathology screening; pregnant person preterm birth screening with cervical length measurement); Third Trimester (fetal growth surveillance; continued preterm birth risk surveillance).

CONCLUSION

Antenatal reproductive screening has multiple elements, is complex, is time-consuming, and requires the use of pre- and post-testing counselling for most screening elements. The use of preconception and trimesters 'one to three' requires clear patient understanding and buy-in. Informed consent and knowledge transfer is a main goal for antenatal reproductive screening approaches.

Incorporation of vasa previa screening into a routine anomaly scan: A single center cohort study

INTRODUCTION

Vasa previa (VP), defined as unprotected fetal vessels traversing the membranes over the cervix, is associated with a high perinatal mortality when undiagnosed prenatally. Conversely, prenatal diagnosis with ultrasound and cesarean delivery before the membranes rupture is associated with excellent outcomes. However, controversy exists regarding screening for VP. In the UK, routine screening for VP is not recommended. The objective of this study was to report the incidence of VP and our experience in the detection of VP with a universal screening protocol at the time of the second-trimester fetal anomaly scan with third-trimester confirmation in an unselected population of pregnancies.

MATERIAL AND METHODS

We performed a single-center historical cohort study of all pregnant women who underwent routine second-trimester anomaly screening scans at West Middlesex University Hospital, London, UK, between 2012 and 2016. Over 5 years, every patient undergoing routine anomaly screening was evaluated for VP using a systematic protocol during their 20-week anomaly scan. Suspected cases of VP were rescanned in the third trimester by specialist sonographers with an interest in VP. The primary outcomes were the incidence and detection of VP.

RESULTS

During the study period, 24 690 anatomy scans were performed. A total of 64 patients were identified as having potential VP at the second-trimester anomaly screening scan, of which 19 were confirmed by the specialist sonographer in the third trimester and at delivery. The screen positive rate was 0.26% (95% confidence interval [CI] 0.20%-0.32%). VP at birth was found in 19/24690 births (1:1299 [95% CI: 1:832-1:2030] births). Universal screening for VP using our protocol had a sensitivity of 100% and a specificity of 99.78% (95% CI: 99.72%-99.84%). The false-positive rate of the second-trimester screen was 0.18% (95% CI: 0.13-0.24). There were no false positives or false negatives at delivery. Of the 19 patients with confirmed VP, 17 had scheduled cesarean deliveries, and two required emergency deliveries due to antepartum hemorrhage. One baby died, giving a perinatal mortality of 5%.

CONCLUSIONS

VP complicates approximately 1:1300 pregnancies. Routine screening for VP yielded a 100% detection rate. We suggest the inclusion of structured VP assessment in standard fetal anomaly screening programs.

Vasa Previa and the Role of Fetal Fibronectin and Cervical Length Surveillance: A Review

Vasa previa is a pregnancy complication that occurs when unprotected fetal blood vessels traverse the cervical os, placing the fetus at high risk of exsanguination and fetal death. These fetal vessels may be compromised by fetal movement and compression, leading to poor oxygen distribution and asphyxiation. Diagnostic tools for vasa previa management and preterm labor (PTL) include transvaginal ultrasound, cervical length (CL) surveillance and use of fetal fibronectin (FFN) testing. These tools can prove to be quite useful as they allow for lead time in the prediction of PTL and spontaneous rupture of membranes which can result in devastating outcomes for pregnancies affected by vasa previa. We conducted a literature review on vasa previa management and the usefulness of FFN and CL surveillance in predicting PTL and found 36 related papers. Although there is limited research available to show the impact of FFN and CL surveillance in the management of vasa previa, there is sufficient evidence to support FFN and CL surveillance in predicting the onset of PTL, which can have devastating consequences for the pregnancies affected. It can be extrapolated that these tools, by helping to determine pregnancies at risk for PTL, could improve management and outcomes in patients with vasa previa. Future studies investigating the management of vasa previa with FFN and CL surveillance to reduce the burden of PTL and its associated comorbidities are warranted.

Type III Vasa Previa Associated with Resolution of a Low-Lying Placenta: Case Report and Literature Review

Vasa previa occurs when fetal vessels lie above the cervical os. A novel type of vasa previa, known as type III, is characterized by an abnormal branching of fetal vessels from the placenta in the absence of velamentous cord insertion (as seen in type I) or multilobed placenta (as seen in type II). Here, we present a case of a type III vasa previa after a resolution of a low-lying placenta. The presence of any known risk factors of vasa previa, including low-lying placenta, should prompt screening for vasa previa in the third trimester. Accurate and timely diagnosis of vasa previa will confer significant survival benefit for the neonate.

Prenatal Diagnosis of Vasa Previa in the Second Trimester of Pregnancy Based on Non-typical Ultrasound Findings: A Case Report and Mini-Review of the Literature

Vasa previa is a rare disorder of the placenta. The absence of a prenatal diagnosis is associated with increased perinatal morbidity and mortality. In our patient, ultrasound findings, although atypical, successfully established the prenatal diagnosis of vasa previa in the second trimester of pregnancy. Despite the fact that the placenta was not low-lying, that it was not possible to visualize the site of umbilical cord insertion into the placental tissue, and that vasa previa was not directly visualized, the presence of blood flow near and around the internal cervical os, as seen on transvaginal Doppler ultrasound in the second and third trimesters of pregnancy, raised serious suspicion of their presence. With the completion of the 36th gestational week, it was decided to proceed with a scheduled cesarean section. One week earlier, a course of corticosteroids was administered. The cesarean section was performed without complications. After placental delivery, the presence of velamentous umbilical cord insertion was noted, with umbilical vessels coursing unprotected by the placental tissue or umbilical cord within the fetal membranes. The puerperant and the newborn were discharged from the obstetrics clinic of the General Hospital of Trikala in excellent condition. This paper highlights the importance of transvaginal color Doppler ultrasound in the prenatal diagnosis of vasa previa, which, while posing little risk to the mother, can often be fatal to the fetus.

Guideline No. 441: Antenatal Fetal Health Surveillance

OBJECTIVE

To summarize the current evidence and to make recommendations for antenatal fetal health surveillance (FHS) to detect perinatal risk factors and potential fetal decompensation in the antenatal period and to allow for timely intervention to prevent perinatal morbidity and/or mortality.

TARGET POPULATION

Pregnant individuals with or without maternal, fetal, or pregnancy-associated perinatal risk factors for antenatal fetal decompensation.

OPTIONS

To use basic and/or advanced antenatal testing modalities, based on risk factors for potential fetal decompensation.

OUTCOMES

Early identification of potential fetal decompensation allows for interventions that may support fetal adaptation to maintain well-being or expedite delivery.

BENEFITS, HARMS, AND COSTS

Antenatal FHS in pregnant individuals with identified perinatal risk factors may reduce the chance of adverse outcomes. Given the high false-positive rate, FHS may increase unnecessary interventions, which may result in harm, including parental anxiety, premature or operative birth, and increased use of health care resources. Optimization of surveillance protocols based on evidence-informed practice may improve perinatal outcomes and reduce harm.

EVIDENCE

Medline, PubMed, Embase, and the Cochrane Library were searched from inception to January 2022, using medical subject headings (MeSH) and key words related to pregnancy, fetal monitoring, fetal movement, stillbirth, pregnancy complications, and fetal sonography. This document represents an abstraction of the evidence rather than a methodological review.

VALIDATION METHODS

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and weak recommendations).

INTENDED AUDIENCE

All health care team members who provide care for or education to obstetrical patients, including maternal fetal medicine specialists, obstetricians, family physicians, midwives, nurses, nurse practitioners, and radiologists.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Directive clinique no 441 : Surveillance prénatale du bien-être fœtal

OBJECTIF

Résumer les données probantes actuelles et formuler des recommandations pour la surveillance prénatale du bien-être fœtal afin de détecter les facteurs de risque périnatal et toute potentielle décompensation fœtale et de permettre une intervention rapide en prévention de la morbidité et la mortalité périnatales.

POPULATION CIBLE

Personnes enceintes avec ou sans facteurs maternels, fœtaux ou gravidiques associés à des risques périnataux et à la décompensation fœtale.

OPTIONS

Utiliser des examens prénataux par technologie de base et/ou avancée en fonction des facteurs de risque de décompensation fœtale. RéSULTATS: La reconnaissance précoce de toute décompensation fœtale potentielle permet d'intervenir de façon à favoriser l'adaptation fœtale pour maintenir le bien-être ou à accélérer l'accouchement. BéNéFICES, RISQUES ET COûTS: Chez les personnes enceintes ayant des facteurs de risque périnatal confirmés, la surveillance du bien-être fœtal contribue à réduire le risque d'issue défavorable. Compte tenu du taux élevé de faux positifs, la surveillance du bien-être fœtal peut augmenter le risque d'interventions inutiles, ce qui peut avoir des effets nuisibles, dont l'anxiété parentale, l'accouchement prématuré ou assisté et l'utilisation accrue des ressources de soins de santé. L'optimisation des protocoles de surveillance d'après des pratiques fondées sur des données probantes peut améliorer les issues périnatales et réduire les effets nuisibles. DONNéES PROBANTES: Des recherches ont été effectuées dans les bases de données Medline, PubMed, Embase et Cochrane Library, de leur création jusqu'à janvier 2022, à partir de termes MeSH et de mots clés liés à la grossesse, à la surveillance fœtale, aux mouvements fœtaux, à la mortinaissance, aux complications de grossesse et à l'échographie fœtale. Le présent document est un résumé des données probantes et non pas une revue méthodologique. MéTHODES DE VALIDATION: Les auteurs ont évalué la qualité des données probantes et la force des recommandations en utilisant le cadre méthodologique GRADE (Grading of Recommendations Assessment, Development and Evaluation). Voir l'annexe A en ligne (tableau A1 pour les définitions et tableau A2 pour l'interprétation des recommandations fortes et faibles). PROFESSIONNELS CONCERNéS: Tous les membres de l'équipe de soins qui prodiguent des soins ou donnent de l'information aux patientes en obstétrique, notamment les spécialistes en médecine fœto-maternelle, les obstétriciens, les médecins de famille, les sages-femmes, les infirmières, les infirmières praticiennes et les radiologistes. DÉCLARATIONS SOMMAIRES: RECOMMANDATIONS.