Vasa previa: time to make a difference

Intrauterine fetal death due to rupture of umbilical vessels: a rare case of furcate cord insertion

Furcate cord insertion refers to the separation of umbilical vessels before reaching the placenta, where the branching vessels normally attach at the edge of the placental parenchyma or near the placental membranes. This is an extremely rare abnormal umbilical cord insertion. This paper reported a case of a furcate cord insertion, where the rupture of exposed umbilical vessels led to intrauterine fetal death at full term. Through literature review, we analyzed the prenatal ultrasound characteristics and pregnancy outcomes of furcate cord insertions, with the aim to improve detection rates and reduce the risk of adverse pregnancy outcomes.

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.

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.

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.

Impact of Universal Vasa Previa Screening With Color Doppler During the OB Ultrasound Anatomy Scan

OBJECTIVES

Our institution introduced universal vasa previa (VP) screening utilizing transabdominal ultrasound with color Doppler for all pregnancies at the second trimester anatomy scan. Our study sought to describe the clinical impact of this intervention.

METHODS

Radiology records from the 12 months pre- and post-intervention were queried for "vasa previa." Records included for analysis were those with a first-time diagnosis or discussion of VP at the anatomy scan. Cases were categorized by outcome: (Group 1) True VP, with subgroups A, unresolved by time of delivery and B, resolved by delivery; (Group 2) False positives; (Group 3) Possible VP without definitive diagnosis; and (Group 4) VP ruled out, for example, "no features of VP." Group size was expressed as a percentage of total anatomy scans during pre- or post-intervention periods respectively. Absolute and relative percent change were calculated for each group.

RESULTS

In the pre-intervention period, 1 case (0.36% of total scans) was categorized in Group 1A, 1 case (0.36%) in Group 3, and 7 cases (2.53%) in Group 4. In the post-intervention period, 2 cases (0.30%) were in Group 1A, 4 cases (0.61%) in Group 1B, 2 cases (0.30%) in Group 2, 1 case (0.15%) in Group 3, and 7 cases (1.06%) in Group 4. There was a +153% relative change in true positives, from 0.36 to 0.91%.

CONCLUSIONS

Universal color Doppler screening may have increased detection (sensitivity) while simultaneously increasing false positives (decreased specificity). While decreasing sensitivity is not ideal, this is acceptable given the potential catastrophic outcome of a missed VP.

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.

Intrauterine death in vasa previa without hemorrhage: case reports

Antepartum and intrapartum hemorrhage from vasa previa (VP) is one of the main causes of intrauterine fetal death (IUFD). Here, we present two cases with type I VP in which velamentous cord insertion below the fetal head and overlying the cervix were reported by prenatal ultrasound scanning, and IUFD occoured after 35 weeks with no signs of prenatal bleeding but with engaged fetal head at presentation. We hypothesized that the IUFD may attributed to the compression of the unprotected umbilical vessels by the engaged fetal head. Thus we suggest that VP with a velamentous cord insertion should be considered for earlier termination of the pregnancy to avoid the risk of non-hemorrhagic adverse fetal outcomes.

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.

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.

What fetal medicine specialists should know about the monochorionic placenta

Monochorionic twins are at risk of transfusion imbalances as long as they are connected to the shared placenta during their intrauterine journey. This review article addresses the macroscopic examination of the monochorionic placenta at the time of birth and explains placental dye injection studies to document the vascular anastomoses and placental sharing. We elaborate on the different types of anastomoses, the importance of how the placenta is divided between the twins, and the angioarchitecture in twin-twin transfusion syndrome, twin anemia polycythemia sequence and selective fetal growth restriction.

Pregnancy and Delivery Outcomes in Women With Persistent Versus Resolved Low-Lying Placenta in the Late Third Trimester

OBJECTIVES

The safest mode of delivery in low-lying placenta is debatable. Little is known about outcomes in low-lying placenta resolved during the late third trimester. We compare outcomes of women with persistent versus resolved low-lying placenta.

METHODS

A retrospective analysis on a prospective cohort of women with low-lying placenta confirmed at 28-30 weeks sonography (01/2009 to 03/2018). Women were followed up serially every 2 to 3 weeks until delivery to assess the placental edge-to-internal os distance (IOD), and included if scan was performed within 28 days before delivery.

RESULTS

There were 86 women: in 21 the low-lying placenta resolved, whereas in 65 persisted (n = 15 IOD 1-10 mm, n = 50 IOD 11-20 mm). Antepartum bleeding associated with higher rates of urgent cesarean delivery in 1-10 mm (P = .041) but not in 11-20 mm (P = 1.000) and >20 mm (P = .333). Among women with IOD >10 mm allowed to labor, vaginal delivery occurred in 76.7% (11-20 mm) and 94.1% (>20 mm) (P = .155), with no difference according to parity (70% and 80% in multiparas, P = .696; 60% and 72.7% in nulliparas, P = .698). Severe PPH (P = .922) and hemoglobin drop (P = .109) were similar among groups. Women with IOD 11-20 mm and >20 mm and vaginal delivery bled less than women with similarly located placenta and cesarean delivery (P = .009 and P = .048).

CONCLUSIONS

Women with IOD >10 mm have high chances of deliver vaginally with no further increase of their hemorrhagic risk. Success of vaginal delivery is independent of parity and antepartum bleeding. Labor should be managed in an adequate hospital setting.

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.