The Characteristics and Obstetric Outcomes of Type II 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.

Succenturiate Placental Lobe Abruption

Placental development is a complex process which sets the stage for normal fetal development. Any variation/disruption occurring during the initial stages of placental formation leads to placental malfunction causing increased maternal-fetal morbidity and mortality. The succenturiate lobe is a structural variation of the placenta that usually appears as a distinct lobe from the main placental mass. Succenturiate lobe is a rare placental anomaly, with high risk of fetal distress, hemorrhage, abruptio placentae and even fetal death because the vessels of this succenturiate lobe are vulnerable to both compression and laceration. Prenatal imaging diagnosis of this pathology improves the fetal prognosis through more careful surveillance and, in case of complications such as abruptio placentae, by shortening the time-to-decision making in favor of cesarean delivery. We present the case of a 27-year-old patient, without risk factors for placental abnormalities, diagnosed antenatally with succenturiate placenta, who presented at 34 weeks of pregnancy for abruptio placentae.

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.

Prenatal diagnosis of bilobate placenta: incidence, risk factors and impact on pregnancy outcomes

OBJECTIVES

To investigate the incidence and risk factors of bilobate placenta, as well as to assess its impact on preeclampsia (PE), preterm delivery (PTD) and small-for-gestational age (SGA) neonates.

METHODS

A prospective study of singleton pregnancies, undergoing routine anomaly scan at 20+0-23+6 gestational weeks, was conducted, between 2018 and 2022. The impact of prenatally diagnosed bilobate placenta on PE, PTD and SGA was assessed. Multivariate logistic regression models were employed to assess the independent association between bilobate placenta and the main pregnancy outcomes, using specific confounders. Additionally, a risk factor analysis was performed.

RESULTS

The study population included 6,454 pregnancies; the incidence of prenatally diagnosed bilobate placenta was 2.0 % (n=129). Bilobate placenta was associated with PE (aOR: 1.721; 95 % CI: 1.014-2.922), while no statistically significant association was found between this anatomical variation and SGA (aOR: 1.059; 95 % CI: 0.665-1.686) or PTD (aOR: 1.317; 95 % CI: 0.773-2.246). Furthermore, pregnancies with prenatally diagnosed bilobate placenta had an increased prevalence of abnormal cord insertion (marginal or velamentous) (9.8 vs. 27.1 %; p<0.001) and increased mean UtA PI z-score (0.03 vs. 0.23; p=0.039). Conception via ART (aOR: 3.669; 95 % CI: 2.248-5.989), previous history of 1st trimester miscarriage (aOR: 1.814; 95 % CI: 1.218-2.700) and advancing maternal age (aOR: 1.069; 95 % CI: 1.031-1.110) were identified as major risk factors for bilobate placenta.

CONCLUSIONS

Bilobate placenta, excluding cases of co-existing vasa previa, is associated with higher incidence of PE, increased mean UtA PI z-score and higher probability of abnormal cord insertion, but not with increased risk for SGA or PTD. It is more common in pregnancies following ART and in women with a previous 1st trimester miscarriage.

The Impact of Assisted Reproductive Technology on Umbilical Cord Insertion: Increased Risk of Velamentous Cord Insertion in Singleton Pregnancies Conceived through ICSI

Background and Objectives: Vasa previa (VP) is a significant perinatal complication that can have serious consequences for the fetus/neonate. Velamentous cord insertion (VCI) is a crucial finding in prenatal placental morphology surveillance as it is indicative of comorbid VP. Assisted reproductive technology (ART) has been identified as a risk factor for VCI, so identifying risk factors for VCI in ART could improve VP recognition. This study aims to evaluate the displacement of umbilical cord insertion (CI) from the placental center and to examine the relationship between the modes of conception. Materials and Methods: We conducted a retrospective study at the Obstetrics Department of Osaka Metropolitan University Hospital in Japan between May 2020 and June 2022. The study included a total of 1102 patients who delivered after 22 weeks of gestation. They were divided into three groups: spontaneous pregnancy, conventional in vitro fertilization (cIVF), and in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI). We recorded patient background information, perinatal complications, perinatal outcomes, and a numerical "displacement score", indicating the degree of separation between umbilical CI and the placental center. Results: The displacement score was significantly higher in the cIVF and IVF/ICSI groups compared with the spontaneous conception group. Additionally, the IVF/ICSI group showed a significantly higher displacement score than the cIVF group. Conclusions: Our study provides the first evidence that the methods of ART can affect the location of umbilical CI on the placental surface. Furthermore, we found that IVF/ICSI may contribute to greater displacement of CI from the placental center.

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.

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.

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.