Prenatally Diagnosed Vasa Previa: A Single-Institution Series of 96 Cases

The potential impact of universal screening for vasa previa in the prevention of stillbirths

OBJECTIVES

To estimate the number of pregnancies complicated by vasa previa annually in nine developed countries, and the potential preventable stillbirths associated with undiagnosed cases. We also assessed the potential impact of universal screening for vasa previa on reducing stillbirth rates.

METHODS

We utilized nationally-reported birth and stillbirth data from public databases in the United States, United Kingdom, Canada, Germany, Ireland, Greece, Sweden, Portugal, and Australia. Using the annual number of births and the number and rate of stillbirths in each country, and the published incidence of vasa previa and stillbirth rates associated with the condition, we estimated the expected annual number of cases of vasa previa, those that would result in a livebirth, and the potential preventable stillbirths with and without prenatal diagnosis.

RESULTS

There were 6,099,118 total annual births with 32,550 stillbirths, corresponding to a summary stillbirth rate of 5.34 per 1,000 pregnancies. The total expected vasa previa cases was estimated to be 5,007 (95 % CI: 3,208-7,201). The estimated number of livebirths would be 4,937 (95 % CI: 3,163-7,100) and 3,610 (95 % CI: 2,313-5,192) in pregnancies with and without a prenatal diagnosis of VP. This implies that prenatal diagnosis would potentially prevent 1,327 (95 % CI: 850-1,908) stillbirths in these countries, corresponding to a potential reduction in stillbirth rate by 4.72 % (95 % CI: 3.80-5.74) if routine screening for vasa previa was performed.

CONCLUSIONS

Our study highlights the importance of universal screening for vasa previa and suggests that prenatal diagnosis of prevention could potentially reduce 4-5 % of stillbirths.

Magnetic resonance imaging diagnosis of abnormal placental cord insertions

INTRODUCTION

Abnormal placental cord insertions (APCIs) are significant risk factors for pregnancy complications, encompassing marginal cord insertion (MCI), velamentous cord insertion (VCI), and vasa previa (VP). While ultrasound is the primary imaging modality, its accuracy can be limited by factors such as maternal obesity and fetal positioning. Complementary to ultrasound, magnetic resonance imaging (MRI) offers a more precise visualization of the fetus, placenta, and umbilical cord relationships. This study aims to investigate the diagnostic value of prenatal magnetic resonance imaging (MRI) for APCIs compared with prenatal ultrasound.

METHODS

We retrospectively collected data from 613 patients who underwent prenatal placental ultrasound and MRI. Of those who were confirmed as APCIs through surgery or pathology, the prenatal MRI features were compared with prenatal ultrasound. The diagnostic efficacy of prenatal MRI and ultrasound for APCIs was assessed based on the clinicopathological findings.

RESULTS

Fifty-six patients were confirmed as APCIs by surgery or pathology, comprising 31 marginal cord insertions (MCIs), 18 velamentous cord insertions (VCIs), 5 vasa previa (VP) cases, and 2 VCI cases combined with VP. Ultrasound examination showed 55.36 % sensitivity (31/56) and 98.38 % specificity (486/494) in diagnosing APCIs, whereas MRI demonstrated 87.50 % sensitivity (49/56) and 98.88 % specificity (531/537).

CONCLUSION

For APCIs complicated by placental location or morphological abnormalities, MRI demonstrates superior diagnostic efficacy compared to ultrasound in late pregnancy.

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 Type 3: Advocating for universal screening and investigation of risk factors: A case report

Vasa previa is a critical obstetric condition marked by unprotected fetal vessels near the cervical os, traditionally divided into Types 1 and 2, based on its association with velamentous cord insertion and accessory placental lobes, respectively. The recent introduction of Type 3 vasa previa addresses atypical cases. We report a unique intrapartum diagnosis of Type 3 vasa previa in a 39-year-old at 38 weeks of gestation, identified during labor induction without prior risk indicators. Despite lacking traditional risk factors, advanced imaging and clinical vigilance led to a primary cesarean delivery, confirming the diagnosis through intraoperative findings of three aberrant vessels with marginal cord insertion. This case emphasizes the critical importance of considering vasa previa in prenatal and intrapartum care to prevent adverse outcomes, advocating for universal screening practices to identify this rare but significant condition.

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.

Inpatient versus outpatient management of prenatally diagnosed vasa praevia: A systematic review and meta-analysis

OBJECTIVE

Vasa praevia is a serious pregnancy complication that is potentially life-threatening for the fetus. The possible benefits of prophylactic hospital admission of asymptomatic women diagnosed with vasa praevia antenatally remain unclear. This study aims to compare the pregnancy outcomes of inpatient versus outpatient management in women with a prenatal diagnosis of vasa praevia.

METHODS

A systematic search of four electronic databases was conducted and two reviewers independently screened studies for eligibility. The inclusion criteria incorporated studies with prenatally diagnosed vasa praevia, a distinction on whether women were managed as inpatients and/or outpatients and where perinatal mortality was recorded as an outcome. The primary outcome of the study was perinatal mortality with additional outcomes of perinatal morbidity, need for emergency caesarean and antenatal steroid administration. Reporting of the results followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.

RESULTS

The search produced 2,300 studies with ten of these studies included in the qualitative synthesis and four included in the quantitative analysis. There was no significant difference in perinatal mortality (OR 1.12, 95 % CI 0.10-12.07, p = 0.93, I2 = 0 %) or morbidity between women managed as inpatients or outpatients. The prophylactic inpatient group had higher rates of earlier gestational delivery and antenatal corticosteroid administration (OR 10.78, 95 % CI 1.07-108.74, p = 0.04, I2 = 82 %), but lower rates of emergency caesareans (OR 0.35, 95 % CI 0.17-0.72, p = 0.004, I2 = 0 %).

CONCLUSION

There were no significant differences in perinatal mortality or morbidity rates observed between inpatient and outpatient management of asymptomatic women with antenatally diagnosed vasa praevia. However, outpatient management is associated with prolonged gestation, a decrease in antenatal corticosteroid administration, and higher odds of emergency caesarean. Outpatient management of prenatally diagnosed vasa praevia seems appropriate for carefully selected asymptomatic women.

Incidence and causes of perinatal death in prenatally diagnosed vasa previa: a systematic review and meta-analysis

OBJECTIVE

This study aimed to estimate the perinatal mortality associated with prenatally diagnosed vasa previa and to determine what proportion of those perinatal deaths are directly attributable to vasa previa.

DATA SOURCES

The following databases have been searched from January 1, 1987, to January 1, 2023: PubMed, Scopus, Web of Science, and Embase.

STUDY ELIGIBILITY CRITERIA

Our study included all studies (cohort studies and case series or reports) that had patients in which a prenatal diagnosis of vasa previa was made. Case series or reports were excluded from the meta-analysis. All cases in which prenatal diagnosis was not made were excluded from the study.

METHODS

The programming language software R (version 4.2.2) was used to conduct the meta-analysis. The data were logit transformed and pooled using the fixed effects model. The between-study heterogeneity was reported by I2. The publication bias was evaluated using a funnel plot and the Peters regression test. The Newcastle-Ottawa scale was used to assess the risk of bias.

RESULTS

Overall, 113 studies with a cumulative sample size of 1297 pregnant individuals were included. This study included 25 cohort studies with 1167 pregnancies and 88 case series or reports with 130 pregnancies. Moreover, 13 perinatal deaths occurred among these pregnancies, consisting of 2 stillbirths and 11 neonatal deaths. Among the cohort studies, the overall perinatal mortality was 0.94% (95% confidence interval, 0.52-1.70; I2=0.0%). The pooled perinatal mortality attributed to vasa previa was 0.51% (95% confidence interval, 0.23-1.14; I2=0.0%). Stillbirth and neonatal death were reported in 0.20% (95% confidence interval, 0.05-0.80; I2=0.0%) and 0.77% (95% confidence interval, 0.40-1.48; I2=0.0%) of pregnancies, respectively.

CONCLUSION

Perinatal death is uncommon after a prenatal diagnosis of vasa previa. Approximately half of the cases of perinatal mortality are not directly attributable to vasa previa. This information will help in guiding physicians in counseling and will provide reassurance to pregnant individuals with a prenatal diagnosis of vasa previa.

Third-trimester fetoscopic ablation therapy for types II and III vasa previa

BACKGROUND

Vasa previa is an obstetrical condition in which fetal vessels located near the cervix traverse the fetal membranes unprotected by underlying placenta. Type I vasa previa arises directly from a velamentous cord root, whereas types II and III arise from an accessory lobe or a distal lobe of the same placenta, respectively. Fetoscopic laser ablation for types II and III vasa previa is a novel therapeutic option with benefits that include surgical resolution of the vasa previa, avoidance of prolonged hospitalization, and opportunity for a term vaginal delivery. The potential risks of fetoscopy can be mitigated by delaying laser surgery until a gestational age of 31 to 33 weeks, immediately before anticipated hospitalized surveillance.

OBJECTIVE

This study aimed to assess feasibility and outcomes of types II and III vasa previa patients treated via fetoscopic laser ablation in the third trimester.

STUDY DESIGN

This is a retrospective study of singleton pregnancies with types II and III vasa previa treated with fetoscopic laser ablation at a gestational age ≥31 weeks at a single center between 2006 and 2022. Pregnancy and newborn outcomes were assessed. Continuous variables are expressed as mean±standard deviation.

RESULTS

Of 84 patients referred for vasa previa, 57 did not undergo laser ablation: 19 either had no or resolved vasa previa, 25 had type I vasa previa (laser-contraindicated), and 13 had type II or III vasa previa but declined laser treatment. Of the remaining 27 patients who underwent laser ablation, 7 were excluded (laser performed at <31 weeks and/or twins), leaving 20 study patients. The mean gestational age at fetoscopic laser ablation was 32.0±0.6 weeks, and total operative time was 62.1±19.6 minutes. There were no perioperative complications. All patients had successful occlusion of the vasa previa vessels (1 required a second procedure). All patients were subsequently managed as outpatients. The mean gestational age at delivery was 37.2±1.8 weeks, the mean birthweight was 2795±465 g, and 70% delivered vaginally. Neonatal intensive care unit admission occurred in 3 cases: 1 for respiratory distress syndrome and 2 for hyperbilirubinemia requiring phototherapy. There were no cases of neonatal transfusion, intraventricular hemorrhage, sepsis, patent ductus arteriosus, or death.

CONCLUSION

Laser ablation for types II and III vasa previa at 31 to 33 gestational weeks was technically achievable and resulted in favorable outcomes.

Inpatient vs outpatient management of pregnancies with vasa previa: A historical cohort study

INTRODUCTION

Vasa previa, a condition where unprotected fetal blood vessels lie in proximity to the internal cervical opening, is a potentially lethal obstetric complication. The precarious situation of these vessels increases the risk of fetal hemorrhage with spontaneous or artificial rupture of membranes, frequently causing fetal/neonatal demise or severe morbidity. As a result, in many centers, inpatient management forms the mainstay when vasa previa is diagnosed antenatally. This study aimed to determine whether a subpopulation of pregnancies diagnosed antenatally with vasa previa could be safely managed as outpatients.

MATERIAL AND METHODS

We reviewed all cases of vasa previa in singleton pregnancies, with no fetal anomalies, diagnosed at Mount Sinai Hospital, Toronto, from January 2008 to December 2017. Cases were categorized into three arms for analysis: outpatients (OP), asymptomatic hospitalized (ASH) and symptomatic hospitalized (SH). The SH arm included patients admitted with any antepartum bleeding or suspicious fetal non-stress test. Those that presented with symptomatic uterine activity/threatened preterm labor and delivered within 7 days of diagnosis were excluded from the study. Records were analyzed for details on hospitalization, antenatal corticosteroid administration, cervical length measurements, and fetal/neonatal mortality and morbidity.

RESULTS

Of the 84 antenatally-diagnosed cases of vasa previa, 47 fulfilled eligibility criteria. A total of 15 cases were managed as OP, 22 as ASH and 10 as SH. Unplanned cesareans were highest in the SH arm (40% vs. 0% ASH vs. 13.3% OP). Those in the SH arm delivered earliest (median 33.8 weeks, interquartile range (IQR) 33.2-34.3 weeks). Of the asymptomatic patients, those in the ASH arm delivered earlier than those in the OP arm (35.3 [34.6-36.2] weeks vs. 36.7 [35.6-37.2] weeks, p = 0.037). There were no cases of fetal/neonatal death, anemia or severe neonatal morbidity and no significant differences between groups based on cervical length or antenatal corticosteroid administration.

CONCLUSIONS

Our study suggests that asymptomatic women with an antenatal diagnosis of vasa previa, singleton pregnancies, and at low risk for preterm birth may safely managed as outpatients, as long as they are able to access hospital promptly in the event of antepartum bleeding or early labor.

Incidence of vasa praevia: a systematic review and meta-analysis

OBJECTIVES

To derive accurate estimates of the incidence of vasa praevia (VP) in a routine population of unselected pregnancies.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

A search of MEDLINE, EMBASE, CINAHL and the Cochrane database was performed to review relevant citations reporting outcomes in pregnancies with VP from January 2000 until 5 April 2023.

ELIGIBILITY CRITERIA FOR SELECTION OF STUDIES

Prospective or retrospective cohort or population studies that provided data regarding VP cases in routine unselected pregnancies during the study period. We included studies published in the English language after the year 2000 to reflect contemporary obstetric and neonatal practice.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently screened the retrieved citations and extracted data. The methodological quality of studies was assessed using the Newcastle-Ottawa Scale, and Preferred Reporting Items for Systematic reviews and Meta-Analyses was used to ensure standardised reporting of studies.

RESULTS

A total of 3847 citations were screened and 82 full-text manuscripts were retrieved for analysis. There were 24 studies that met the inclusion criteria, of which 12 studies reported prenatal diagnosis with a systematic protocol of screening. There were 1320 pregnancies with VP in a total population of 2 278 561 pregnancies; the weighted pooled incidence of VP was 0.79 (95% CI: 0.59 to 1.01) per 1000 pregnancies, corresponding to 1 case of VP per 1271 (95% CI: 990 to 1692) pregnancies. Nested subanalysis of studies reporting screening for VP based on a specific protocol identified 395 pregnancies with VP in a population of 732 654 pregnancies with weighted pooled incidence of 0.82 (95% CI: 0.53 to 1.18) per 1000 pregnancies (1 case of VP per 1218 (95% CI: 847 to 1901) pregnancies).

CONCLUSION

The incidence of VP in unselected pregnancies is 1 in 1218 pregnancies. This is higher than is previously reported and can be used as a basis to assess whether screening for this condition should be part of routine clinical practice. Incorporation of strategies to screen for VP in routine clinical practice is likely to prevent 5% of stillbirths.

PROSPERO REGISTRATION NUMBER

CRD42020125495.

Vasa Previa

Vasa previa refers to unprotected fetal vessels running through the membranes over the cervix. Until recently, this condition was associated with an exceedingly high perinatal mortality rate attributable to fetal exsanguination when the membranes ruptured. However, ultrasonography has made it possible to diagnose the condition prenatally, allowing cesarean delivery before labor or rupture of the membranes. Several recent studies have indicated excellent outcomes with prenatally diagnosed vasa previa. However, outcomes continue to be dismal when vasa previa is undiagnosed before labor. Risk factors for vasa previa include second-trimester placenta previa and low-lying placentas, velamentous cord insertion, placentas with accessory lobes, in vitro fertilization, and multifetal gestations. Recognition of individuals who are at risk and screening them will greatly decrease the mortality rate from this condition. Because of the relative rarity of vasa previa, there are no randomized controlled trials to guide management. Therefore, recommendations on the diagnosis and management of vasa previa are based largely on cohort studies and expert opinion. This Clinical Expert Series review addresses the epidemiology, pathophysiology, natural history, diagnosis and management of vasa previa, as well as innovative treatments for the condition.

Perinatal Mortality Despite Prenatal Diagnosis of Vasa Previa: A Systematic Review

OBJECTIVE

To determine the causes and potential preventability of perinatal deaths in prenatally identified cases of vasa previa.

DATA SOURCES

Reports of prenatally identified cases of vasa previa published in the English language literature since 2000 were identified in Medline and ClinicalTrials.gov with the search terms "vasa previa," "abnormal cord insertion," "velamentous cord," "marginal cord," "bilobed placenta," and "succenturiate lobe."

METHODS OF STUDY SELECTION

All cases from the above search with an antenatally diagnosed vasa previa present at delivery in singleton or twin gestations with perinatal mortality information were included.

TABULATION, INTEGRATION, AND RESULTS

Cases meeting inclusion criteria were manually abstracted, and multiple antenatal, intrapartum, and outcome variables were recorded. Deaths and cases requiring neonatal transfusion were analyzed in relation to plurality, routine hospitalization, and cervical length monitoring. A total of 1,109 prenatally diagnosed cases (1,000 singletons, 109 twins) were identified with a perinatal mortality rate attributable to vasa previa of 1.1% (95% CI 0.6-1.9%). All perinatal deaths occurred with unscheduled deliveries. The perinatal mortality rate in twin pregnancies was markedly higher than that in singleton pregnancies (9.2% vs 0.2%, P <.001), accounting for 80% of overall mortality despite encompassing only 9.8% of births. Compared with individuals with singleton pregnancies, those with twin pregnancies are more likely to undergo unscheduled delivery (56.4% vs 35.1%, P =.01) despite delivering 2 weeks earlier (33.2 weeks vs 35.1 weeks, P =.006). An institutional policy of routine hospitalization is associated with a reduced need for neonatal transfusion (0.9% vs 6.0%, P <.001) and a reduction in the perinatal mortality rate in twin pregnancies (0% vs 25%, P =.002) but not in singleton pregnancies (0% vs 0.5%, P =.31).

CONCLUSION

Routine hospitalization and earlier delivery of twins may result in a reduction in the perinatal mortality rate. A smaller benefit from routine admission of individuals with singleton pregnancies cannot be excluded. There is currently insufficient evidence to recommend the routine use of cervical length measurements to guide clinical management.

Guideline No. 439: Diagnosis and Management of Vasa Previa

OBJECTIVE

To summarize the current evidence and to make recommendations for diagnosis and classification of vasa previa and for management of women with this diagnosis.

TARGET POPULATION

Pregnant women with vasa previa or low-lying fetal vessels.

OPTIONS

To manage vasa previa in hospital or at home, and to perform a cesarean delivery preterm or at term, or to allow a trial of labour when a diagnosis of vasa previa or low-lying fetal vessels is suspected or confirmed.

OUTCOMES

Prolonged hospitalization, preterm birth, rate of cesarean delivery, and neonatal morbidity and mortality.

BENEFITS, HARMS, AND COSTS

Women with vasa previa or low-lying fetal vessels are at an increased risk of maternal and fetal or postnatal adverse outcomes. These outcomes include a potentially incorrect diagnosis, need for hospitalization, unnecessary restriction of activities, an early delivery, and an unnecessary cesarean delivery. Optimization of diagnostic and management protocols can improve maternal and fetal or postnatal outcomes.

EVIDENCE

Medline, Pubmed, Embase, and the Cochrane Library were searched from inception to March 2022, using medical subject headings (MeSH) and keywords related to pregnancy, vasa previa, low-lying fetal vessels, antepartum hemorrhage, short cervix, preterm labour, and cesarean delivery. This document presents 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

Obstetric care providers, including obstetricians, family physicians, nurses, midwives, maternal-fetal medicine specialists, and radiologists.

TWEETABLE ABSTRACT

Unprotected fetal vessels in placental membranes and cord that are close to the cervix, including vasa previa, need careful characterization by sonographic examination and evidence-based management to reduce risks to the baby and the mother during pregnancy and delivery.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Directive clinique no 439: Diagnostic et prise en charge du vasa prævia

OBJECTIF

Résumer les données probantes actuelles et énoncer des recommandations pour le diagnostic et la classification du vasa prævia et pour la prise en charge des femmes ayant reçu ce diagnostic.

POPULATION CIBLE

Femmes enceintes présentant un vasa prævia ou des vaisseaux ombilicaux péricervicaux.

OPTIONS

En cas de diagnostic soupçonné ou confirmé de vasa prævia ou de vaisseaux ombilicaux péricervicaux, prendre en charge la patiente à l'hôpital ou à domicile, puis pratiquer une césarienne avant terme ou à terme ou entreprendre une épreuve de travail. RéSULTATS: Hospitalisation prolongée, accouchement prématuré, césarienne et morbidité et mortalité néonatales. BéNéFICES, RISQUES ET COûTS: Les femmes ayant un vasa prævia ou des vaisseaux ombilicaux péricervicaux présentent un risque accru d'issues défavorables maternelles, fœtales ou postnatales, à savoir un diagnostic potentiellement erroné, un besoin d'hospitalisation, une restriction inutile des activités, un accouchement précoce et une césarienne inutile. L'optimisation des protocoles de diagnostic et de prise en charge peut améliorer les issues maternelles, fœtales et postnatales. DONNéES PROBANTES: Des recherches ont été effectuées dans les bases de données Medline, PubMed, Embase et Cochrane Library, de leur création jusqu'à mars 2022, à partir de termes MeSH et de mots clés liés à la grossesse, au vasa prævia, aux vaisseaux prævia, à l'hémorragie ante partum, au col court, au travail prématuré et à la césarienne. 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: Fournisseurs de soins obstétricaux, y compris obstétriciens, médecins de famille, infirmières, sages-femmes, spécialistes en médecine fœto-maternelle et radiologistes. RéSUMé POUR TWITTER: En cas de cordon et de vaisseaux ombilicaux non protégés dans les membranes près du col (vasa prævia y compris), une caractérisation échographique et une prise en charge avisée s'imposent pour réduire les risques pour le bébé et la mère pendant la grossesse et l'accouchement.

Current Evidence on Vasa Previa without Velamentous Cord Insertion or Placental Morphological Anomalies (Type III Vasa Previa): Systematic Review and Meta-Analysis

Vasa previa carries a high risk of severe fetal morbidity and mortality due to fetal hemorrhage caused by damage to unprotected fetal cord vessels upon membrane rupture. Vasa previa is generally classified into types I and II. However, some cases are difficult to classify, and some studies have proposed a type III classification. This study aimed to review the current evidence on type III vasa previa. A systematic literature search was conducted, and 11 articles (2011-2022) were included. A systematic review showed that type III vasa previa accounts for 5.7% of vasa previa cases. Thirteen women with type III vasa previa were examined at a patient-level analysis. The median age was 35 (interquartile range [IQR] 31.5-38) years, and approximately 45% were assisted reproductive technology (ART) pregnancies. The median gestational week of delivery was 36 (IQR 34-37) weeks; the antenatal detection rate was 84.6%, and no cases reported neonatal death. The characteristics and obstetric outcomes (rate of ART, antenatal diagnosis, emergent cesarean delivery, gestational age at delivery, and neonatal mortality) were compared between types I and III vasa previa, and all outcomes of interest were similar. The current evidence on type III vasa previa is scanty, and further studies are warranted.

The Characteristics and Obstetric Outcomes of Type II Vasa Previa: Systematic Review and Meta-Analysis

Vasa previa is a rare fetal life-threatening obstetric disease classified into types I and II. This study aimed to examine the characteristics and obstetric outcomes of type II vasa previa. A systematic review was performed, and 20 studies (1998-2022) were identified. The results from six studies showed that type II vasa previa accounted for 21.3% of vasa previa cases. The characteristics and obstetric outcomes (rate of assisted reproductive technology (ART), antenatal diagnosis, emergent cesarean delivery, maternal transfusion, gestational age at delivery, and neonatal mortality) were compared between type I and II vasa previa, and all outcomes of interest were similar. The association between ART and abnormal placenta (bilobed placenta or succenturiate lobe) was examined in three studies, and the results were as follows: (i) increased rate of succenturiate lobes (ART versus non-ART pregnancy; OR (odds ratio) 6.97, 95% confidence interval (CI) 2.45-19.78); (ii) similar rate of abnormal placenta (cleavage-stage versus blastocyst embryo transfer); (iii) increased rate of abnormal placenta (frozen versus fresh embryo transfer; OR 2.97, 95%CI 1.10-7.96). Although the outcomes of type II vasa previa appear to be similar to those of type I vasa previa, the current evidence is insufficient for a robust conclusion.

Placental and Umbilical Cord Anomalies Diagnosed by Two- and Three-Dimensional Ultrasound

The aim of this review is to present a wide spectrum of placental and umbilical cord pathologies affecting the pregnancy. Placental and umbilical cord anomalies are highly associated with high-risk pregnancies and may jeopardize fetal well-being in utero as well as causing a predisposition towards poor perinatal outcome with increased fetal and neonatal mortality and morbidity. The permanent, computerized perinatology databases of different international centers have been searched and investigated to fulfil the aim of this manuscript. An extended gallery of prenatal imaging with autopsy correlation in specific cases will help to provide readers with a useful iconographic tool and will assist with the understanding and definition of this critical obstetrical and perinatological issue.

Timing of birth and adverse pregnancy outcomes in cases of prenatally diagnosed vasa previa: a systematic review and meta-analysis

OBJECTIVE

The ideal time for birth in pregnancies diagnosed with vasa previa remains unclear. We conducted a systematic review aiming to identify the gestational age at delivery that best balances the risks for prematurity with that of pregnancy prolongation in cases with prenatally diagnosed vasa previa.

DATA SOURCES

Ovid MEDLINE, PubMed, CINAHL, Embase, Scopus, and Web of Science were searched from inception to January 2022.

STUDY ELIGIBILITY CRITERIA

The intervention analyzed was delivery at various gestational ages in pregnancies prenatally diagnosed with vasa previa. Cohort studies, case series, and case reports were included in the qualitative synthesis. When summary figures could not be obtained directly from the studies for the quantitative synthesis, authors were contacted and asked to provide a breakdown of perinatal outcomes by gestational age at birth.

METHODS

Study appraisal was completed using the National Institutes of Health quality assessment tool for the respective study types. Statistical analysis was performed using a random-effects meta-analysis of proportions.

RESULTS

The search identified 3435 studies of which 1264 were duplicates. After screening 2171 titles and abstracts, 140 studies proceeded to the full-text screen. A total of 37 studies were included for analysis, 14 of which were included in a quantitative synthesis. Among 490 neonates, there were 2 perinatal deaths (0.4%), both of which were neonatal deaths before 32 weeks' gestation. In general, the rate of neonatal complications decreased steadily from <32 weeks' gestation (4.6% rate of perinatal death, 91.2% respiratory distress, 11.4% 5-minute Apgar score <7, 23.3% neonatal blood transfusion, 100% neonatal intensive care unit admission, and 100% low birthweight) to 36 weeks' gestation (0% perinatal death, 5.3% respiratory distress, 0% 5-minute Apgar score <7, 2.9% neonatal blood transfusion, 29.2% neonatal intensive care unit admission, and 30.9% low birthweight). Complications then increased slightly at 37 weeks' gestation before decreasing again at 38 weeks' gestation.

CONCLUSION

Prolonging pregnancies until 36 weeks' gestation seems to be safe and beneficial in otherwise uncomplicated pregnancies with antenatally diagnosed vasa previa.

Vasa previa: A rare obstetric complication-A case series and a literature review

Vasa previa is a rare condition. However, since the increase in assisted reproductive technologies (ARTs), clinicians are more frequently confronted with this complication. In this study, we present five cases of vasa previa prenatally diagnosed from a tertiary referral hospital with approximately 2000 births yearly.

Vasa previa: when antenatal diagnosis can change fetal prognosis

OBJECTIVES

Evaluate ultrasound diagnostic accuracy, maternal-fetal characteristics and outcomes in case of vasa previa diagnosed antenatally, postnatally or with spontaneous resolution before delivery.

METHODS

Monocentric retrospective study enrolling women with antenatal or postnatal diagnosis of vasa previa at Sant'Anna Hospital in Turin from 2007 to 2018. Vasa previa were defined as fetal vessels that lay 2 cm within the uterine internal os using 2D and Color Doppler transvaginal ultrasound. Diagnosis was confirmed at delivery and on histopathological exam. Vasa previa with spontaneous resolutions were defined as fetal vessels that migrate >2 cm from uterine internal os during scheduled ultrasound follow-ups in pregnancy.

RESULTS

We enrolled 29 patients (incidence of 0.03%). Ultrasound antenatally diagnosed 25 vasa previa (five had a spontaneous resolution) while four were diagnosed postnatally, with an overall sensitivity of 96.2%, specificity of 100%, positive predictive value of 96.2%, and negative predictive value of 100%. Early gestational age at diagnosis is significally associate with spontaneously resolution (p 0.023; aOR 1.63; 95% IC 1.18-2.89). Nearly 93% of our patient had a risk factor for vasa previa: placenta previa at second trimester or low-lying placenta, bilobated placenta, succenturiate cotyledon, velametous cord insertion or assisted reproduction technologies.

CONCLUSIONS

Maternal and fetal outcomes in case of vasa previa antenatally diagnosed are significally improved. Our data support the evaluation of umbilical cord insertion during routine second trimester ultrasound and a targeted screening for vasa previa in women with risk factor: it allows identification of fetus at high risk, reducing fetal mortality in otherwise healthy newborns.

Placental Types and Effective Perinatal Management of Vasa Previa: Lessons from 55 Cases in a Single Institution

BACKGROUND

We aimed to identify clinical characteristics and outcomes for each placental type of vasa previa (VP).

METHODS

Placental types of vasa previa were defined as follows: Type 1, vasa previa with velamentous cord insertion and non-type 1, vasa previa with a multilobed or succenturiate placenta and vasa previa with vessels branching out from the placental surface and returning to the placental cotyledons.

RESULTS

A total of 55 cases of vasa previa were included in this study, with 35 cases of type 1 and 20 cases of non-type 1. Vasa previa with type 1 showed a significantly higher association with assisted reproductive technology, compared with non-type 1 (p = 0.024, 60.0% and 25.0%, respectively). The diagnosis was significantly earlier in the type 1 group than in the non-Type 1 group (p = 0.027, 21.4 weeks and 28.6 weeks, respectively). Moreover, the Ward technique for anterior placentation to avoid injury of the placenta and/or fetal vessels was more frequently required in non-type 1 cases (p < 0.001, 60.0%, compared with 14.3% for type 1).

CONCLUSION

The concept of defining placental types of vasa previa will provide useful information for the screening of this serious complication, improve its clinical management and operative strategy, and achieve more preferable perinatal outcomes.

Systematic screening for vasa previa at the 20-week anomaly scan

INTRODUCTION

The presence of vasa previa carries a high risk for severe fetal morbidity and mortality due to fetal bleeding caused by injury to unprotected fetal vessels when rupture of membranes occurs. Previously, it has been shown that prenatal diagnosis significantly improves the outcome. However, systematic screening for vasa previa is not generally performed and clinical studies demonstrating the performance of systematic screening for vasa previa in routine clinical practice are rare. The objective of this study was to assess the performance of systematic screening for vasa previa by determining placental cord insertion at the 20-week anomaly scan.

MATERIAL AND METHODS

This is a retrospective study of 6038 pregnant women between 18+0 and 24+0 gestational weeks who were prospectively screened for vasa previa by depiction of the site of placental cord insertion at the 20-week anomaly scan. Pregnancies with marginal or velamentous cord insertion underwent vaginal sonography for examination for vasa previa. In cases with succenturiate or bilobed placentas, the bridging vessels were depicted, and vaginal sonography was performed if necessary.

RESULTS

There were 21 cases of vasa previa and all were diagnosed prenatally. In 18 cases, the cord insertion was marginal or velamentous. The remaining three cases had placental anomalies, which necessitated a detailed examination. All pregnancies with vasa previa were delivered at a mean of 35.2 (SD 1.8) gestational weeks by cesarean section. Among pregnancies affected by vasa previa, all fetuses survived. The median birthweight was 2390 g (range 1200-2990 g) and the mean umbilical artery pH 7.34 (SD 0.04). The median 5-min APGAR score was nine (range 7-10). None of the fetuses or neonates died or required blood transfusions. In all pregnancies of the whole cohort which were complicated by fetal or neonatal demise and in neonates with a 5-min APGAR score ≤5 and/or an umbilical artery pH ≤7.10, fetal blood loss was excluded as a cause of the poor obstetric outcome.

CONCLUSIONS

Screening for vasa previa is feasible and efficient, taking into account the site of placental cord insertion in pregnancies not affected by placenta previa and bilobed and succenturiate placenta.

Perinatal outcome of pregnancies with prenatal diagnosis of vasa previa: systematic review and meta-analysis

OBJECTIVES

To derive accurate estimates of perinatal survival in pregnancies with and without a prenatal diagnosis of vasa previa based on a systematic review of the literature and meta-analysis.

METHODS

A search of MEDLINE, EMBASE and The Cochrane Library was performed to review relevant citations reporting on the perinatal outcomes of pregnancies with vasa previa. We included prospective and retrospective cohort and population studies that provided data on pregnancies with a prenatal diagnosis of vasa previa or cases diagnosed at birth or following postnatal placental examination. Meta-analysis using a random-effects model was performed to derive weighted pooled estimates of perinatal survival (excluding stillbirths and neonatal deaths) and intact perinatal survival (additionally excluding hypoxic morbidity). Incidence rate difference (IRD) meta-analysis was used to estimate the significance of differences in pooled proportions between cases of vasa previa with and those without a prenatal diagnosis. Heterogeneity between studies was estimated using Cochran's Q and the I² statistic.

RESULTS

We included 21 studies reporting on the perinatal outcomes of 683 pregnancies with a prenatal diagnosis of vasa previa. There were three stillbirths (1.01% (95% CI, 0.40-1.87%)), five neonatal deaths (1.19% (95% CI, 0.52-2.12%)) and 675 surviving neonates, resulting in a pooled estimate for perinatal survival of 98.6% (95% CI, 97.6-99.3%). Based on seven studies that included cases of vasa previa with and without a prenatal diagnosis, the pooled perinatal survival in pregnancies without a prenatal diagnosis (61/118) was 72.1% (95% CI, 50.6-89.4%) vs 98.6% (95% CI, 96.7-99.7%) in cases with a prenatal diagnosis (224/226). Therefore, the risk of perinatal death was 25-fold higher when a diagnosis of vasa previa was not made antenatally, compared with when it was (odds ratio (OR), 25.39 (95% CI, 7.93-81.31); P < 0.0001). Similarly, the risk of hypoxic morbidity was increased 50-fold in cases with vasa previa without a prenatal diagnosis compared with those with a prenatal diagnosis (36/61 vs 5/224; OR, 50.09 (95% CI, 17.33-144.79)). The intact perinatal survival rate in cases of vasa previa without a prenatal diagnosis was significantly lower than in those with a prenatal diagnosis (28.1% (95% CI, 14.1-44.7%) vs 96.7% (95% CI, 93.6-98.8%)) (IRD, 73.4% (95% CI, 53.9-92.7%); Z = -7.4066, P < 0.001).

CONCLUSIONS

Prenatal diagnosis of vasa previa is associated with a high rate of perinatal survival, whereas lack of an antenatal diagnosis significantly increases the risk of perinatal death and hypoxic morbidity. Further research should be undertaken to investigate strategies for incorporating prenatal screening for vasa previa into routine clinical practice. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Monochorionic Diamniotic Vasa Previa Pregnancy: A Medical Student Perspective

Monochorionic diamniotic twins and vasa previa are uncommon. We present a case that was followed from ultrasound diagnosis to delivery.

Vasa previa: Perinatal outcomes in singleton and multiple pregnancies

Vasa previa (VP) is a rare and life-threatening condition for the fetus. It is associated with increased perinatal mortality rates. The current study sought to retrospectively analyze the perinatal outcomes of VP in singleton and multiple pregnancies between January 1, 2013 and December 31, 2019 at a tertiary hospital in west China. One hundred and fifty-seven cases of VP were identified, including 131 singletons, 23 twins and 3 triplets. VP in 20 cases was diagnosed at delivery. There were 183 live births. Neonatal mortality was significantly higher in cases with no prenatal diagnosis (9.7% vs. 1.3%, p = 0.035). There was a significantly higher rate of NICU admission, premature infant and neonatal pneumonia in cases with prenatal diagnosis (p < 0.05). Among twin pregnancies with VP as a prenatal diagnosis, there were significantly earlier gestational age at admission (31.1 vs. 34.1 weeks, p = 0.000) and delivery age (33.4 vs. 35.3 weeks, p = 0.000) than those among singleton pregnancies. The neonatal mortality in twins with prenatal diagnosis was significantly higher than that in singletons (0% vs. 6.9%, p = 0.037). Early hospitalization of VP in the third trimester may be reasonable. The data suggest that the timing of elective delivery at 34-36 weeks in singletons and 32-34 weeks in twins may be suitable. It should be emphasized to make corresponding optimal delivery time according to individual differences for the women, especially in twin pregnancy.

Are we over-diagnosing vasa praevia? The experience and lessons learned in a tertiary centre

BACKGROUND

Vasa praevia (VP) is a rare obstetric condition in which unprotected fetal vessels transverse the cervix, are vulnerable to rupture during labour and may result in rapid exsanguination of the fetus. Antenatal diagnosis of VP has resulted in excellent outcomes. However, there are little data available on the false positive rates for the antenatal diagnosis of VP. Improving accuracy of the diagnosis of VP can potentially improve outcomes and reduce unnecessary intervention.

AIMS

To assess our accuracy in the diagnosis of VP, examine our false positive diagnoses of VP and suggest strategies during antenatal ultrasound to aid in the antenatal diagnosis of VP.

MATERIAL AND METHODS

We conducted a retrospective descriptive study of women diagnosed with VP antenatally over 11 years at a single tertiary hospital and eligible patients were identified from obstetric databases. All medical records, including ultrasound reports, were reviewed and compared with the placental histological findings and both operative and midwifery documentation of the cord insertion.

RESULTS

Twenty-three women (25 babies) were diagnosed with VP and underwent a caesarean section delivery at a mean gestational age of 36 weeks. The false positive rate in our series was 17% (4/23).

CONCLUSIONS

Our study highlights the importance of postnatal confirmation of the diagnosis of VP and careful documentation of intraoperative findings of the placenta and cord insertion. We suggest strategies to aid in the accurate diagnosis of VP, thereby improving clinical decision-making and reducing unnecessary intervention.

Prenatally diagnosed vasa previa: association with adverse obstetrical and neonatal outcomes

BACKGROUND

Vasa previa represents a rare prenatal finding with potentially life-threatening risk to the fetus.

OBJECTIVE

This study aimed to describe the natural history of prenatally diagnosed vasa previa and evaluate the association between antenatally diagnosed vasa previa and adverse obstetrical and neonatal outcomes.

STUDY DESIGN

This was a multicenter descriptive and retrospective study of patients diagnosed prenatally with vasa previa on transvaginal ultrasound in the New York City Maternal-Fetal Medicine Research Consortium centers between 2012 and 2018. Outcomes evaluated included persistence of vasa previa at the time of delivery, gestational age at delivery, indications for unplanned unscheduled delivery, and neonatal course.

RESULTS

A total of 165 pregnancies with vasa previa were included, of which 16 were twin gestations. Forty-three cases (26.1%) were noted to resolve on subsequent ultrasound. Of the remaining 122 cases with persistent vasa previa, 46 (37.7%) required unscheduled delivery. Twin gestations were nearly 3 times as likely to require unscheduled delivery as singleton gestations (73.3% vs 25.2%; P<.001). Most infants (70%) were admitted to the neonatal intensive care unit. There was 1 neonatal death (0.9%) because of complications related to prematurity.

CONCLUSION

Despite the low neonatal mortality rate with prenatal detection of vasa previa, one-third of patients required unscheduled delivery, and more than half of neonates experienced complications related to prematurity.

Adverse perinatal outcome and placental abnormalities in pregnancies with major fetal congenital heart defects: A retrospective case-control study

OBJECTIVE

The placental development has been shown to be compromised in pregnancies affected by fetal congenital heart defects (CHD). This study aimed to investigate the frequency of complications related to utero-placental insufficiency in pregnancies with and without major CHD.

METHOD

This retrospective case-control study was conducted at a Fetal Echocardiography Center in Milan. The following outcomes were compared between the two groups: preeclampsia (PE), small for gestational age (SGA), placental disorders and preterm birth (PTB). The logistic regression analysis was adjusted for maternal age, parity, co-morbidities and mode of conception.

RESULTS

The CHD group (n = 480) showed significantly increased incidence of PE (2.9% vs 0.9%; aOR, 6.50; 95% CI, 1.39-30.41; P = .017) as compared to the control group (n = 456). Placental disorders occurred more frequently in the CHD than in controls, but the increased risk showed only a borderline significance (4.5% vs 3.3%; aOR, 2.56; 95% CI, 0.99-1.02; P = .046). There was a significantly higher risk of SGA in CHD than in controls (8.7% vs 3.9%; aOR, 3.37; 95% CI, 1.51-7.51; P = .003). PTB occurred in 65/477 (13.6%) cases and in 39/447 (8.7%) controls (P = .022) (aOR, 2.17; 95% CI, 1.24-3.81; P = .007).

CONCLUSION

Major CHD are significantly associated with the risk of PE, SGA and PTB.

Fetoscopic Laser Ablation Therapy for Type II Vasa Previa

BACKGROUND

In type II vasa previa, fetoscopic laser ablation has the potential to avoid prolonged hospitalization, elective prematurity, and cesarean delivery associated with traditional conservative management.

OBJECTIVE

To assess the feasibility and to report perinatal outcomes of type II vasa previa patients treated via fetoscopic laser ablation.

STUDY DESIGN

This is a retrospective descriptive study of all women with vasa previa treated with laser at our center between 2006 and 2019. After 2010, laser ablation of vasa previa was only offered after 31 gestational weeks. Continuous variables are expressed as means ± SD.

RESULTS

33 patients were evaluated for laser ablation of suspected vasa previa. Fifteen were not candidates (7 had type I vasa previa and 8 had no vasa previa), and the 18 remaining had type II vasa previa. Ten (56%) elected to undergo in utero laser ablation of the vasa previa vessel(s), which was successful in all patients. The mean gestational age (GA) at the time of the procedure was 28.8 ± 5.4 weeks, and the total operative time was 48.1 ± 21.3 min; there were no perioperative complications. The number of vessels lasered were distributed as follows: 1 (2 cases), 2 (5 cases), and 3 (3 cases). All patients except for 1 were subsequently managed as outpatients. The mean GA at delivery was 35.5 ± 3.2 weeks, and vaginal delivery occurred in 5 cases. The 5 patients with singletons who underwent laser ablation for primary diagnosis of type II vasa previa after the protocol change in 2010 had the following outcomes: mean GA of surgery was 32.5 ± 0.8 weeks, mean GA at delivery was 38.1 ± 1.4 weeks, vaginal delivery occurred in all cases, mean birth weight was 2,965 ± 596 g, and none were admitted to the neonatal intensive care unit.

CONCLUSION

This cohort represents the largest number of vasa previa cases treated via in utero laser reported to date. Laser occlusion of type II vasa previa was technically achievable in all cases and resulted in favorable outcomes.

Prevention of stillbirth: impact of two-stage screening for vasa previa

OBJECTIVES

To examine the feasibility and effectiveness of a two-stage ultrasound screening strategy for detection of vasa previa and to estimate the potential impact of screening on prevention of stillbirth.

METHODS

This was a retrospective study of data from prospective screening for vasa previa in singleton pregnancies, undertaken at the Fetal Medicine Unit at Medway Maritime Hospital, UK, between 2012 and 2018. Women booked for prenatal care and delivery in our hospital had routine ultrasound examinations at 11-13 and 20-22 weeks' gestation. Those with velamentous cord insertion at the inferior part of the placenta at the first-trimester scan and those with low-lying placenta at the second-trimester scan were classified as high-risk for vasa previa and had transvaginal sonography searching specifically for vasa previa, at the time of the 20-22-week scan. The management and outcome of cases with suspected vasa previa is described. We excluded cases of miscarriage or termination at < 24 weeks' gestation.

RESULTS

The study population of 26 830 singleton pregnancies included 21 (0.08%; 1 in 1278) with vasa previa. In all cases of vasa previa, the diagnosis was made at the 20-22-week scan and confirmed postnatally by gross and histological examination of the placenta. At the 11-13-week scan, cord insertion was classified as central in 25 071 (93.4%) cases, marginal in 1680 (6.3%), and velamentous in 79 (0.3%). In 16 (76.2%) of the 21 cases of vasa previa, cord insertion at the first-trimester scan was classified as velamentous at the inferior part of the placenta, in two cases (9.5%) as marginal and in three cases (14.3%) as central. The 21 cases of vasa previa were managed on an outpatient basis with serial scans for measurement of cervical length and elective Cesarean section at 34 weeks' gestation; all babies were liveborn but there was one neonatal death. In the study population, there were 83 stillbirths, none of which had evidence of vasa previa on postnatal examination. On the assumption that, if we had not diagnosed prenatally all 21 cases of vasa previa in our population, half of these cases would have resulted in stillbirth, then the potential impact of screening is prevention of 10.6% (10/94) of stillbirths.

CONCLUSION

A two-stage strategy of screening for vasa previa can be incorporated into routine clinical practice, and such a strategy could potentially reduce the rate of stillbirth. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Variations in reported outcomes in studies on vasa previa: a systematic review

OBJECTIVE

To evaluate reported outcomes of published studies on the diagnosis and management of vasa previa in pregnancy.

MATERIALS AND METHODS

Databases such as MEDLINE, Embase, Cochrane, PubMed, and ClinicalTrials.gov were searched up to March 2018 for all published studies on vasa previa using combinations of the following medical subject headings and key words: vasa previa, placenta previa, low-lying placenta, succenturiate lobe or placenta, bilobed or bilobate placenta, and velamentous insertion. All original human research that described maternal, obstetric, placental, fetal or neonatal outcomes relating to pregnancies with vasa previa were included for analysis. Title and abstract screening and data extraction was conducted independently and in duplicate by 2 reviewers for all studies until total agreement for eligibility was achieved. Data extraction was also conducted in duplicate in approximately 50% of studies reviewed.

RESULTS

A total of 160 published studies (1004 pregnancies) were included. There was a wide range of reported outcomes, many of which were sparingly reported. The most commonly reported maternal outcomes included mode of delivery, presence of antepartum hemorrhage, time of diagnosis, and rupture of membranes. The presence of known risk factors for vasa previa such as a low-lying placenta, succenturiate or bilobed placenta, and (velamentous) cord insertion was incorrectly reported as "outcomes" in many studies. The most commonly reported fetal/neonatal outcomes included fetal heart rate, gestational age at delivery, birthweight, Apgar score, presence of neonatal anemia, cord blood gas measurements, need for blood transfusion, and death. Of note, only 3 studies reported outcomes related to life impact, maternal social and emotional functioning, perceived delivery of care, or resource utilization.

CONCLUSION

Despite the profound effect the diagnosis of vasa previa has on pregnant women, families, and healthcare systems, studies on vasa previa seldom report outcomes related to life impact and resource utilization. There is a need for the development of a core outcome set-a minimum standard set of outcomes deemed important by pregnant women and other stakeholders involved in their care-to standardize outcome reporting in future studies on vasa previa.

Vasa previa and associated risk factors: a systematic review and meta-analysis

OBJECTIVE

To systematically review published literature and calculate the prevalence of vasa previa and its known risk factors.

MATERIALS AND METHODS

MEDLINE, Embase, the Cochrane Library, PubMed (non-MEDLINE and in process), and www.clinicaltrials.gov were searched from inception to March 2018 using indexing terms "vasa previa," "placenta previa," "low lying placenta," "succenturiate lobe," "bilobate placenta," "bilobed placenta," and "velamentous insertion." All original research studies reporting on 5 or more pregnancies with vasa previa were included. The search was limited to studies on human data and those published in the English language. Two reviewers independently screened titles and abstracts, completed data extraction, and assessed reporting quality using the Study Quality Assessment Tool for Case Series Studies of the National Heart, Lung, and Blood Institute. Disagreements were discussed and resolved at each step of the process.

RESULTS

We included 21 studies that reported 428 pregnancies with vasa previa of 1,027,918 deliveries (0.46 cases of vasa previa per 1000 deliveries). These studies fared well on risk of bias assessment using the Study Quality Assessment Tool for Case Series Studies of the National Heart, Lung, and Blood Institute. The prevalence and 95% confidence intervals of known risk factors for vasa previa included a low-lying placenta (61.5%, 53.0%-70.0%), velamentous cord insertion (52.2%, 39.6%-64.7%), bilobed or succenturiate lobed placenta (33.3%, 20.9%-45.7%), use of in vitro fertilization (26.4%, 16.0%-36.8%), and multiple gestation (8.92%, 5.33%-12.5%).

CONCLUSION

Vasa previa affects 0.46 cases per 1000 pregnancies. Given the high prevalence of prenatally detectable risk factors in affected pregnancies, the cost-effectiveness of screening strategies for vasa previa either in isolation, using a risk factor-based approach, or universally, in tandem with cervical-length screening using transvaginal ultrasound, should be revisited.

Vasa previa: prenatal diagnosis and management

PURPOSE OF REVIEW

Vasa previa is a rare disorder of placentation associated with a high rate of perinatal morbidity and mortality when undetected before delivery. We have evaluated the recent evidence for prenatal diagnosis and management of vasa previa.

RECENT FINDINGS

Around 85% of cases of vasa previa have one or more identifiable risk factors including in-vitro fertilization, multiple gestations, bilobed, succenturiate or low-lying placentas, and velamentous cord insertion. The development of standardized prenatal targeted scanning protocols may improve perinatal outcomes. There is no clear consensus on the optimal surveillance strategy including the need for hospitalization, timing of corticosteroids administration and the value of transvaginal cervical length measurements. Outpatient management is possible if there is no evidence of cervical shortening on ultrasound and there are no symptoms of bleeding or uterine contractions. Recent national guidelines and expert reviews have recommended scheduled cesarean section of all asymptomatic women presenting with vasa previa between 34 and 36 weeks' gestation.

SUMMARY

Prenatal diagnosis of vasa previa is pivotal to prevent intrapartum fetal death. Although there is insufficient evidence to support the universal mid-gestation ultrasound screening for vasa previa, recent evidence indicates the need for standardized prenatal targeted screening protocols of pregnancies at high-risk of vasa previa.

Vasa previa and extreme prematurity: a population-based study

OBJECTIVE

To determine population-based risks of preterm birth associated with vasa previa.

STUDY DESIGN

Included were 945,950 singleton, live birth cesarean deliveries with and without vasa previa (gestational ages 24-41 weeks) in California between 2007 and 2012. Odds ratios (ORs) of preterm birth were estimated using logistic regression.

RESULTS

In total, 586 were complicated by vasa previa (0.06%). In total, 369 (63%) of those with vasa previa were delivered <37 weeks, compared with 91,662 (10%) of those without. Odds of extreme and very preterm birth were substantially higher for pregnancies with vasa previa even after controlling for comorbidities known to contribute to prematurity, with ORs of 4.6 (95% confidence interval, CI: 1.7-12.5) and 16.0 (95% CI: 10.3-24.8), respectively.

CONCLUSION

Based on these population-based data, most patients with vasa previa are delivered between 32 and 36 weeks gestation; however, a clinically significant portion occur before 32 weeks. These data are helpful in counseling patients with vasa previa regarding prematurity risk.

Vasa previa screening strategies: decision and cost-effectiveness analysis

OBJECTIVE

To perform a decision and cost-effectiveness analysis comparing four screening strategies for the antenatal diagnosis of vasa previa in singleton pregnancies.

METHODS

A decision-analytic model was constructed comparing vasa previa screening strategies. Published probabilities and costs were applied to four transvaginal screening scenarios that were carried out at the time of mid-trimester ultrasound: no screening, ultrasound-indicated screening, screening only pregnancies conceived by in-vitro fertilization (IVF) and universal screening. Ultrasound-indicated screening was defined as performing transvaginal ultrasound at the time of the routine anatomy ultrasound scan in response to one of the following sonographic findings associated with an increased risk of vasa previa: low-lying placenta, marginal or velamentous cord insertion or bilobed or succenturiate lobed placenta. The primary outcome was cost per quality-adjusted life year (QALY) in US$. The analysis was performed from a healthcare system perspective with a willingness-to-pay threshold of $100 000 per QALY selected. One-way and multivariate sensitivity analysis (Monte-Carlo simulation) was performed.

RESULTS

This decision-analytic model demonstrated that screening pregnancies conceived by IVF was the most cost-effective strategy, with an incremental cost effectiveness ratio (ICER) of $29186.50/QALY. Ultrasound-indicated screening was the second most cost-effective, with an ICER of $56096.77/QALY. These data were robust to all one-way and multivariate sensitivity analyses performed.

CONCLUSIONS

Within the baseline assumptions, transvaginal ultrasound screening for vasa previa appears to be most cost-effective when performed among IVF pregnancies. However, both IVF and ultrasound-indicated screening strategies fall within contemporary willingness-to-pay thresholds, suggesting that both strategies may be appropriate to apply in clinical practice. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Vasa praevia: Should we routinely screen high-risk women for this rare but serious condition?

Vasa praevia is described as the unprotected fetal vessels traversing through the placental membranes over the cervical os, below the fetal presenting part and unprotected by placental tissue or the umbilical cord. It is often not detected antenatally and presents with painless bleeding and rapid fetal compromise after spontaneous or artificial rupture of the membranes, which causes trauma to these vessels. It is a rare condition affecting one in 2500 pregnancies and has a reported perinatal mortality rate of up to 60%. More than 80% of cases of vasa praevia have at least one risk factor for the condition and it has been shown that identification of vasa praevia antenatally results in fetal survival rates of up to 97%. Risk factors include placenta praevia, velamentous cord insertion, bi-lobed placenta, succenturiate lobe, assisted reproduction and multiple pregnancy. Screening for vasa praevia with transvaginal ultrasound has been shown to be sensitive and cost effective when used in a targeted population where risk factors are present. Here, we present the antenatal assessment and management of a case of vasa praevia detected during the routine 20-week anatomy scan of a healthy primigravida, which resulted in elective caesarean section delivery of a healthy baby at 36 weeks' gestation. The pathophysiology of vasa praevia is discussed and the methods and role of screening for this rare but serious condition are appraised.

Vasa Previa: Prenatal Diagnosis and Outcomes: Thirty-five Cases From a Single Maternal-Fetal Medicine Practice

OBJECTIVES

To assess the accuracy and effectiveness of routine screening for vasa previa, to describe our experience, and to assess factors that contribute to missed cases of vasa previa.

METHODS

A retrospective descriptive study of all cases of vasa previa from a single maternal-fetal medicine service between 2009 and 2017 was performed. Ultrasound findings and obstetric and neonatal outcomes were reviewed and analyzed.

RESULTS

Thirty-five cases of vasa previa were identified. Most cases (33 of 35 [94.3%]) were diagnosed antenatally. All 33 cases that followed our screening protocol were diagnosed antenatally and had favorable outcomes. Two cases that did not follow our protocol were not diagnosed antenatally and were delivered emergently. The mean gestational age ± SD at delivery of antenatally diagnosed cases was 34.9 ± 1.69 weeks. All neonates survived.

CONCLUSIONS

Routine ultrasound screening for vasa previa using American Institute of Ultrasound in Medicine criteria will almost universally lead to good outcomes and prevent perinatal mortality.

Society for Maternal-Fetal Medicine (SMFM) Consult Series #44: Management of bleeding in the late preterm period

Third-trimester bleeding is a common complication arising from a variety of etiologies, some of which may initially present in the late preterm period. Previous management recommendations have not been specific to this gestational age window, which carries a potentially lower threshold for delivery. The purpose of this document is to provide guidance on management of late preterm (34 0/7-36 6/7 weeks of gestation) vaginal bleeding. The following are Society for Maternal-Fetal Medicine recommendations: (1) we recommend delivery at 36-37 6/7 weeks of gestation for stable women with placenta previa without bleeding or other obstetric complications (GRADE 1B); (2) we do not recommend routine cervical length screening for women with placenta previa in the late preterm period due to a lack of data on an appropriate management strategy (GRADE 2C); (3) we recommend delivery between 34 and 37 weeks of gestation for stable women with placenta accreta (GRADE 1B); (4) we recommend delivery between 34 and 37 weeks of gestation for stable women with vasa previa (GRADE 1B); (5) we recommend that in women with active hemorrhage in the late preterm period, delivery should not be delayed for the purpose of administering antenatal corticosteroids (GRADE 1B); (6) we recommend that fetal lung maturity testing should not be used to guide management in the late preterm period when an indication for delivery is present (GRADE 1B); and (7) we recommend that antenatal corticosteroids should be administered to women who are eligible and are managed expectantly if delivery is likely within 7 days, the gestational age is between 34 0/7 and 36 6/7 weeks of gestation, and antenatal corticosteroids have not previously been administered (GRADE 1A).

Prenatal diagnosis and management of vasa previa in twin pregnancies: a case series and systematic review

BACKGROUND

Twin pregnancies are at higher risks of velamentous cord insertion and vasa previa. In vitro fertilization is an additional risk factor of abnormal cord insertion and thus the incidence of vasa previa is likely to increase over the next decades.

OBJECTIVE

We sought to evaluate the role of ultrasound imaging in optimizing the management of twins diagnosed with vasa previa antenatally.

STUDY DESIGN

We searched our database for twin pregnancies diagnosed with vasa previa and managed antenatally using measurements of cervical length and performed a systematic review of articles that correlated prenatal diagnosis of vasa previa in twins and pregnancy outcome. PubMed and MEDLINE were searched for studies published from 1987 through October 20, 2016, using specific medical subject heading terms, key words, and their combination. The primary eligibility criteria were articles that correlated prenatal ultrasound imaging of vasa previa and pregnancy outcome in twins. The secondary eligibility criteria was the use of cervical length in the management of twin pregnancies diagnosed antenatally with vasa previa. Two authors independently assessed inclusion criteria, data extraction, and analysis. The final selection included 3 case report series, 9 retrospective cohort studies, and 1 retrospective case-control study of vasa previa diagnosed prenatally and confirmed at birth in twin pregnancies.

RESULTS

The search of our databases identified 6 cases of dichorionic-diamniotic twins and 1 case of monochorionic-diamniotic twins diagnosed prenatally with vasa previa between 22-29 weeks and managed using cervical length. Two cases were delivered by emergency because of rapid changes in cervical length in one and bleeding on placenta previa in the other at 33 and 30 weeks, respectively. The systematic review identified data on 56 cases. The incidence of twin pregnancies diagnosed antenatally with vasa previa in the cohort and case-control studies was 11.0%. Data on chorionicity were available in only 34 cases and cervical length measurements were used by only the authors of 2 case reports and 4 cohort studies. Velamentous cord insertion was the most common additional ultrasound findings in twins presenting with vasa previa in both our series and the systematic review.

CONCLUSION

Vasa previa is associated with specific prenatal and obstetric complications with different outcomes in singletons compared to twins. Data on the diagnosis and management of vasa previa in twin pregnancies are limited but there is enough evidence to warrant guidelines for targeted screening. To enable the development of efficient management protocols tailored to the need of individual cases, future studies of the screening, diagnosis, and management of vasa previa should be prospective and multicentric with detailed data on twins including chorionicity and use of cervical length.