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

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

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

Management strategy and experience of vasa previa in perinatal centers: A nationwide survey in Japan

AIM

To clarify the current situation and outcomes of vasa previa (VP) in Japan.

METHODS

A questionnaire survey on VP was conducted at all 408 perinatal centers in Japan. The content of the survey included (1) the management strategy for pregnant women who were diagnosed with VP and (2) the number and outcomes of VP cases managed between January 2020 and December 2022.

RESULTS

Questionnaires were collected from 220 (53.9%: 220/408) perinatal centers. (1) A total of 78.8% (164/208) of facilities implemented routine hospitalization. Routine hospitalization was initiated at 32 (22-36) [median (range)] weeks of gestation. The timing of planned cesarean section (CS) was at 36 (33.5-39) weeks of gestation in 198 facilities. (2) Of the 220 facilities that responded, 109 (49.5%: 109/220) accommodated patients with VP during the observation period. The total number of VP cases was 351, with a frequency of one case (0-33) per single perinatal center for 3 years. Emergency CS was required in 89 cases (25.4%: 89/351). There were no fetal or neonatal deaths in this study. The number of undiagnosed patients with VP prenatally was seven (2.0%: 7/351). Umbilical vessel rupture occurred in two cases (0.6%: 2/351).

CONCLUSIONS

Current management strategies in Japanese perinatal centers that responded to this survey appear to yield good perinatal outcomes in VP. Additional studies and comparisons are needed to elucidate the necessity of routine hospitalization, the optimal duration of hospitalization, and the timing of planned CS.

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.

Marginal cord insertion in the first trimester is associated with furcate cord insertion

OBJECTIVES

To evaluate the potential connections between marginal cord insertion during the first trimester and furcate cord insertion later in pregnancy.

METHODS

This is a prospective study of screening data on the cord insertion site in 3178 singleton pregnancies. The cord insertion site was examined in two stages. The first stage was screening for the cord insertion site between 10-13 weeks of gestation, the purpose is to determine the category of umbilical cord insertion. The second stage, performed at 22-28 weeks of gestation, was to follow up on the relationship between the cord insertion site and the placenta and to identify any changes in the category of umbilical cord insertion. This was performed to diagnose or exclude furcate cord insertion by identifying whether the umbilical cord trunk separated or branched before it reached the placenta. Factors influencing progression to furcate cord insertion and perinatal complications were assessed.

RESULTS

Fourteen cases (0.44%) with progression to furcate cord insertion, all of which showed marginal cord insertion on ultrasound in the first trimester (p < 0.001). without progression to furcate cord insertion, there were no changes in the category of umbilical cord insertion in 3050 cases (96.40%) compared to the early pregnancy. 114 cases (3.60%) with changes in the category of umbilical cord insertion that was not consistent with furcate cord insertion. A total of 14 cases progressed to furcate cord insertion, all showed the cord insertion site were in close proximity, and 11 (78.57%) cases showed a low insertion site (p < 0.001). Regarding the choice of mode of delivery, elective caesarean delivery was done in 8/14 (57.14%). The incidences of spontaneous vaginal delivery were 5/14 (35.71%) (p < 0.001). One (7.14%) case of progression to furcate cord insertion due to haematoma at the root of the umbilical cord ended with an emergency caesarean section. In terms of perinatal complications, marginal cord insertion that progressed to furcate cord insertion had higher incidences of SGA infants, abnormal placental morphology, retention of the placenta, and cord-related adverse pregnancy outcomes than not progressed to furcate cord insertion (p < 0.05).

CONCLUSIONS

Marginal cord insertion in the first trimester has the potential to progress to furcate cord insertion. We suggest that ultrasound-diagnosed marginal cord insertion in the first trimester should be watched carefully in the second trimester, which is clinically useful to accurately determine the category of cord insertion and to improve the rate of prenatal diagnosis of furcate cord insertion.

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.

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

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

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.

Prenatal diagnosis and postnatal outcome of Type-III vasa previa: systematic review of literature

OBJECTIVE

Type-III vasa previa (VP) is a rare form of VP, not necessarily associated with other placental or vascular anomalies, in which aberrant vessels run from the placenta to the amniotic membranes, near the internal cervical os, before returning to the placenta. Early diagnosis of Type-III VP is important but technically challenging. The objective of this study was to gather the current available evidence on the perinatal diagnosis and outcome of Type-III VP.

METHODS

A systematic review of the literature on the perinatal diagnosis of atypical Type-III VP was carried out in PubMed, MEDLINE and EMBASE accordingto PRISMA guidelines from inception to March 2023. Data extraction and tabulation were performed by two operators and checked by a third senior author. The quality of the included studies was evaluated using the National Institutes of Health tool for the quality assessment of case-series studies. Our local ultrasound database was searched for previously unreported recent cases. Characteristics of prenatally and postnatally diagnosed Type-III VP, including clinical features and perinatal outcomes, were summarized using descriptive statistics.

RESULTS

Eighteen cases of Type-III VP were included, of which 16 were diagnosed prenatally (14 cases were retrieved from 10 publications and two were unpublished cases from our center) and two were diagnosed postnatally (retrieved from two publications). All prenatal cases were diagnosed on transvaginal ultrasound at a mean gestational age of 29 weeks (median, 31 weeks; range, 19-38 weeks). Conception was achieved with in-vitro fertilization in 4/16 (25.0%) cases. There were no prenatal symptoms in 15/18 (83.3%) cases, while in two (11.1%) cases there was vaginal bleeding and in one (5.6%) preterm labor occurred. In 15/18 (83.3%) cases, at least one placental abnormality was observed, including low-lying insertion (9/17), succenturiate or accessory lobe (1/17), velamentous cord insertion (3/18) and marginal insertion (9/18). All prenatally diagnosed cases were liveborn and were delivered by Cesarean section before rupture of membranes at a median gestational age of 35 weeks (range, 32-38 weeks) without neonatal complications. Emergency Cesarean section was performed in 2/16 (12.5%) cases with a prenatal diagnosis and 1/2 (50.0%) cases with a postnatal diagnosis (P = 0.179). Among those with data available, an Apgar score of ≤ 7 was observed in the prenatally vs postnatally diagnosed group in 5/13 vs 1/1 cases, respectively, at the 1-min evaluation and 3/13 vs 1/1 cases, respectively, at the 5-min evaluation.

CONCLUSIONS

The prenatal diagnosis of Type-III VP is challenging, with few cases reported in the literature; however, it is crucial for minimizing the risk of adverse outcome by enabling early-term elective Cesarean delivery prior to rupture of membranes. Given that clinical manifestations and risk factors are non-specific, and that Type-III VP cannot be excluded when there is a normal cord insertion or a singular placental mass, systematic screening by transvaginal ultrasound in the general pregnant population is recommended, particularly in those with a low-lying or morphologically abnormal placenta and those who conceived using assisted reproductive technology. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

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.

Type 3 vasa previa with no low-lying placenta, with central umbilical cord insertion at the upper uterine segment, and with aberrant vessels on the broad membrane: A case report

Type 3 vasa previa is a new concept. Herein, a case is reported of a 35-year-old woman, pregnant following in vitro fertilization, in whom vasa previa was detected on color Doppler ultrasound at 26 weeks, with no finding of a low-lying placenta. A cesarean section was performed at 34 weeks and 3 days. Gross examination of the placenta showed Type 3 vasa previa with findings somewhat different from previous reports: two aberrant fetal vessels with branching on the broad membrane, and central cord insertion which was farther from the longitudinal center of the placenta than were the running vessels on the membrane. Vasa previa cannot be excluded due to normal cord insertion at the upper uterine segment, absence of placenta previa, or a low-lying placenta in the second trimester. Careful ultrasound screening can promote neonatal survival in patients with Type 3 vasa previa.

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.

Relationship between Abnormal Placenta and Obstetric Outcomes: A Meta-Analysis

The placenta has several crucial physiological functions that help maintain a normal pregnancy. Although approximately 2-4% of pregnancies are complicated by abnormal placentas, obstetric outcomes remain understudied. This study aimed to determine the outcomes and prevalence of patients with abnormal placentas by conducting a systematic review of 48 studies published between 1974 and 2022. The cumulative prevalence of circumvallate placenta, succenturiate placenta, multilobed placenta, and placenta membranacea were 1.2%, 1.0%, 0.2%, and 0.004%, respectively. Pregnancies with a circumvallate placenta were associated with an increased rate of emergent cesarean delivery, preterm birth (PTB), and placental abruption compared to those without a circumvallate placenta. The succenturiate lobe of the placenta was associated with a higher rate of emergent cesarean delivery, whereas comparative results were observed in terms of PTB, placental abruption, and placenta previa in comparison to those without a succenturiate lobe of the placenta. A comparator study that examined the outcomes of multilobed placentas found that this data is usually unavailable. Patient-level analysis (n = 15) showed high-rates of abortion (40%), placenta accreta spectrum (40%), and a low term delivery rate (13.3%) in women with placenta membranacea. Although the current evidence is insufficient to draw a robust conclusion, abnormal placentas should be recognized as a high-risk factor for adverse outcomes during pregnancy.