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Magnetic resonance imaging of vasa praevia
... As for MRI, it is a precise examination, which allows a prenatal diagnosis and mapping. However, due to its high cost and unavailability, MRI is not recommended for the diagnosis of vasa previa [4,5]. ...
Vasa previa is a rare complication during pregnancy, involving fetal prognosis by massive fetal hemorrhage. We report a case of Benckiser's hemorrhage that occurred after spontaneous rupture of the membranes. In the light of this work, we will discuss the clinical diagnosis, the possibilities of ultrasound screening and the management modalities.
... 24 Additionally, magnetic resonance imaging has been used to confirm vasa previa in a few obscure cases. 25 In cases wherein vasa previa is suspected, repeated ultrasound assessments should be performed in the third trimester, due to the fact that up to 39% of apparent vasa previa will resolve by the late third trimester. 26 When regarding screening for vasa previa, some authors have established targeted screening strategies. ...
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. Accurate prenatal diagnosis and sufficient management before the onset of labor improve the outcome of pregnancies complicated with vasa previa.
... Bien qu'encore peu utilisée, l'IRM tient une place de plus en plus grande dans le bilan lésionnel de la pathologie foetale, de l'utérus gravide et du placenta (34). ...
L'insertion vélamenteuse du cordon est la cause la plus fréquente d'hémorragie de Benckiser. Pathologie rare mais mortelle pour le foetus dans 75 à 100% des cas, cette hémorragie incercible est une tragédie pour le couple et l'équipe obstétricale. Par une recherche approfondie de la littérature, puis par une étude de cas de la MRAP, nous essaierons de démontrer l'existence de facteurs de risques, ainsi que la possibilité d'une recherche anténatale de vaisseaux courants sur les membranes, permettant une prise en charge adéquate de la mère et du foetus , dans le but d'éviter une hémorragie de Benckiser.
... The diagnosis of vasa previa is commonly made with Doppler US, demonstrating fetal vessels covering the internal os, but findings may also be seen on MR (Fig. 11). Flow voids overlying the internal os may be seen on T2WI, and time-of-flight sequences can demonstrate the direction of flow within the umbilical vessels [39]. ...
The placenta is commonly overlooked on magnetic resonance imaging of the pregnant patient, which is frequently performed for alternative reasons such as to characterize fetal or uterine anomalies or to investigate the etiology of acute pelvic pain in pregnancy. Placental disorders have potential for significant maternal and fetal morbidity and peripartum complications if not recognized and treated in a timely manner. The radiologist must be familiar with normal placental variants and the spectrum of benign to life-threatening conditions affecting the placenta so that the Obstetrician can be promptly notified and patient management altered, if necessary. In this pictorial essay, we will describe our MR protocol for placental imaging, provide an image-rich review of the normal placenta, placental variants, and a variety of pathological conditions affecting the placenta and gravid uterus.
... Threedimensional US also maps out the fetal vessels on the cervical os. In cases of diagnostic uncertainty or the need for additional required information, MRI has an increasing role in the diagnosis of vasa previa, in particular, velamentous cord insertion located at the posterior uterine wall [3,6]. MRI has not been shown to have any adverse fetal effects, and has been proven to be a powerful tool in the evaluation of several fetal and placental abnormalities, providing in several circumstances information superior to that obtained using US alone [6]. ...
Objective: Vasa previa is a rare complication, and rupture of vasa previa during pregnancy may lead to significant perinatal mortality. Here, we report a case of vasa previa evaluated prenatally using noncontrast time-of-flight magnetic resonance angiography (TOF MRA).
Case Report: A 22-year-old primiparous woman was referred to our hospital due to suspicion of vasa previa. Transvaginal ultrasonography showed two vessels running over the internal os. To obtain further information, magnetic resonance imaging (MRI) and TOF MRA were performed. Caesarean section was carried out, and macroscopic findings of the vascular distribution on the fetal membrane were consistent with those identified by TOF MRA.
Conclusion: TOF MRA in addition to MRI may be an option for prenatal identification of the precise three-dimensional vascular distribution in patients with vasa previa.
... This investigation has some advantages over ultrasound due to its accurate description of the vessels, the location, direction, placenta, its structure and the point of attachment, segments and their distribution. However, it is an expensive, relatively not easily accessible and long-lasting visual examination, which generally does not have greater advantages compared to ultrasound colour doplerometry (13). ...
Background. The aim of this article is to present a rare clinical case of vasa praevia as well as to assess the relevance of the problem by reviewing the latest literature sources.
Materials and methods. In this report we present a case of a 33-year-old woman diagnosed with vasa praevia at 33 weeks of pregnancy, after hospitalisation with preterm rupture of membranes following the delivery of a live healthy baby through a lower segment Caesarean section during 33rd week of gestation at Vilnius University Hospital Santari?ki? Clinics. We investigated all the documentation of the patient before and after delivery.
Results and conclusions. Vasa praevia is a rather rare pathology which is likely to occur during pregnancy, may result in heavy bleeding and be particularly threatening to the fetus life. A timely diagnosis for these women is essential. The gold standard for vasa praevia diagnosis is the fetal ultrasound scan. Vasa praevia pathology is found during the routine second trimester ultrasound check-up. The selection of proper tactics applied during pregnancy care is essential. At the gestational age of 28?32, it is advisable to mature fetal lungs as well as the fetus condition should be investigated by a perinatologist. The mode of delivery is the C-section which tends to reduce the frequency of possible complications.
... A 2850 g boy was in the condition of hemorrhagic shock, with Apgar scores of 3 and 5 at 1 and 5 min, respectively. Child's RBC was 2.8×10 12 , hemoglobin concentration was 106 g/L, hematocrit 0.33, thrombocyte count was 204×10 9 and arterial pH 7.407. The baby required immediate resuscitation, including intubation and blood transfusions. ...
Objective: To enlighten vasa praevia as a rare complication of pregnancy associated with a high rate of fetal and neonatal mortality. Early detection of this condition is crucial for planning the therapeutic approach to prevent fetal and neonatal risks. Methods and Results: We report three different cases of vasa praevia: the one that was recognized during labor immediately after amniotomy, causing life threatening hemorrhage and emergency cesarean section with good neonatal outcome; second case where vasa praevia were diagnosed in prenatal period during amnioscopy confirmed by color doppler sonography, enabling elective cesarean section with no consequences; the third case were un-recognized vasa praevia followed by emergency cesarean section and neonatal death. Conclusion: Vasa praevia remains an unpredictable cause of fetal or neonatal death even though it can be relatively easily diagnosed in prenatal period either by color doppler sonography, amnioscopy or magnetic resonance.
... Although MR imaging allows global evaluation of the vascular anatomy, it is generally used only when the diagnosis is in question, or if ultrasonographic evaluation is inadequate. 54 Fig. 14. Placenta accreta in a 36-year-old woman at 31 weeks gestational age. ...
Because of the high maternal morbidity and mortality of undiagnosed placental abnormalities, there is a need for accurate antenatal diagnosis. Important placental features amenable to investigation with magnetic resonance (MR) imaging include variant placental location and morphology, and abnormal implantation or invasion of placenta into the myometrium. MR imaging features permit the diagnosis of abnormal placentation include placental lobulation with uterine contour deformity, interruption of the inner low signal-intensity myometrial layer, and placental heterogeneity resulting from dark intraplacental bands and abnormal vascularity.
... 49 While ultrasound has been suggested to be the most effective diagnostic tool for antenatal diagnosis of VP, some authors have also suggested that Magnetic Resonance Imaging (MRI) may be useful. [50][51][52][53] While there may be some recognised benefits of MRI in providing additional information to both grey-scale and colour Doppler sonography such as greater detail of vessel location prior to CS and further confirmation of the placental forms (e.g. single, placenta praevia, bilobed, succenturiate lobe) when used during the third trimester, 50,52 the cost and extra time required is generally prohibitive. ...
Introduction: Literature addressing the feasibility of prenatal detection of vasa praevia during the mid-trimester morphology ultrasound scan is scarce, as is a lack of consensus about the appropriate management of pregnancies once it is detected.
Method: The following descriptive review will provide historical context about the clinical significance, epidemiology, diagnosis and outcomes of pregnancies complicated by vasa praevia. It will also examine the role of ultrasound in the diagnosis of vasa praevia, and will examine current evidence surrounding this debate of whether routine screening for vasa praevia is possible, beneficial, or cost-effective.
Conclusion: Finally, it will highlight the need for increased research into effective management of pregnancies at high risk of, or affected by vasa praevia to reduce fetal mortality and maternal and fetal morbidity associated with the condition.
... In placenta previa transvaginal US together with Doppler is used to diagnose vasa previa, which are aberrant fetal vessel with risk of rupture. In some cases with bi-lobated placentas assessment may be difficult and MRI could demonstrate the positions of the pla-centas and vessels running over the inner cervical os more clearly [10]. ...
While ultrasound is still the gold standard method of placental investigation, magnetic resonance imaging (MRI) has certain benefits. In advanced gestational age, obese women, and posterior placental location, MRI is advantageous due to the larger field of view and its multiplanar capabilities. Some pathologies are seen more clearly in MRI, such as infarctions and placental invasive disorders. The future development is towards functional placental MRI. Placental MRI has become an important complementary method for evaluation of placental anatomy and pathologies contributing to fetal problems such as intrauterine growth restriction.
... Differential diagnosis includes chorioamniotic separation, normal cord loop, marginal placental vascular sinus, varicosities of the uterine veins, and amniotic band. 26,27 MRI is an accurate tool with which the antenatal diagnosis of vasa previa can be made 28,29 ; however, it is expensive and not widely available, and thus, at present, is not a method that can be used in most obstetric practice to diagnose vasa previa. ...
To describe the etiology of vasa previa and the risk factors and associated condition, to identify the various clinical presentations of vasa previa, to describe the ultrasound tools used in its diagnosis, and to describe the management of vasa previa.
Reduction of perinatal mortality, short-term neonatal morbidity, long-term infant morbidity, and short-term and long-term maternal morbidity and mortality.
Published literature on randomized trials prospective cohort studies, and selected retrospective cohort studies was retrieved through searches of PubMed or Medline, CINAHL, and the Cochrane Library, using appropriate controlled vocabulary (e.g., selected epidemiological studies comparing delivery by Caesarean section with vaginal delivery studies comparing outcomes when vasa previa is diagnosed antenatally vs.intrapartum) and key words (e.g. vasa previa). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. Searches were updated on a regular basis and incorporated into the guideline to October 1, 2008. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies,clinical practice guideline collections, clinical trial registries, and from national and international medical specialty societies.
The evidence collected was reviewed by the Diagnostic Imaging Committee and the Maternal Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on Preventive Health Care. Benefits, Harms, and Costs: The benefit expected from this guideline is facilitation of optimal and uniform care for pregnancies complicated by vasa previa.
The Society of Obstetricians and Gynaecologists of Canada.
... Differential diagnosis includes chorioamniotic separation, normal cord loop, marginal placental vascular sinus, varicosities of the uterine veins, and amniotic band. 26,27 MRI is an accurate tool with which the antenatal diagnosis of vasa previa can be made 28,29 ; however, it is expensive and not widely available, and thus, at present, is not a method that can be used in most obstetric practice to diagnose vasa previa. ...
Objectives
To describe the etiology of vasa previa and the risk factors and associated condition, to identify the various clinical presentations of vasa previa, to describe the ultrasound tools used in its diagnosis, and to describe the management of vasa previa.
Outcomes
Reduction of perinatal mortality, short‐term neonatal morbidity, long‐term infant morbidity, and short‐term and long‐term maternal morbidity and mortality.
Evidence
Published literature on randomized trials prospective cohort studies, and selected retrospective cohort studies was retrieved through searches of PubMed or Medline, CINAHL, and the Cochrane Library, using appropriate controlled vocabulary (e.g., selected epidemiological studies comparing delivery by Caesarean section with vaginal delivery studies comparing outcomes when vasa previa is diagnosed antenatally vs. intrapartum) and key words (e.g. vasa previa). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. Searches were updated on a regular basis and incorporated into the guideline to October 1, 2008. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment‐related agencies, clinical practice guideline collections, clinical trial registries, and from national and international medical specialty societies.
Values
The evidence collected was reviewed by the Diagnostic Imaging Committee and the Maternal Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on Preventive Health Care.
Benefits, Harms, and Costs
The benefit expected from this guideline is facilitation of optimal and uniform care for pregnancies complicated by vasa previa.
Sponsors
The Society of Obstetricians and Gynaecologists of Canada.
Objective
To evaluate reported outcomes of studies published on the diagnosis and management of vasa previa in pregnancy.
Data Sources
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 MeSH and keyword terms: vasa previa, placenta previa, low lying placenta, succenturiate lobe or placenta, bilobed or bilobate placenta, velamentous insertion.
Study Eligibility Criteria
All original human research that described maternal/obstetric/placental and fetal/neonatal outcomes relating to pregnancies with vasa previa were included for analysis.
Study Appraisal and Synthesis Methods
Title/abstract screening and data extraction was conducted independently and in duplicate by two 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 (1,004 pregnancies) were included. There was a wide range of reported outcomes, many of which were sparingly reported. The most commonly reported maternal outcomes included the mode of delivery, presence of antepartum hemorrhage, time of diagnosis and rupture of membranes. Presence of known risk factors for vasa previa such as a low-lying placenta, succenturiate or bi-lobed placenta and (velamentous) cord insertion were incorrectly reported as ‘outcomes’ in many studies. The most commonly reported fetal/neonatal outcomes included fetal heart rate, gestational age at delivery, birth weight, Apgar score, presence of neonatal anemia, cord gas measurements, need for blood transfusion and death. Importantly, only three studies reported outcomes related to life impact, maternal social and emotional functioning, perceived delivery of care or resource utilization.
Conclusions
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 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 praevia (VP) называют состояние, при котором сосуды пло-дового происхождения располагаются в амниотической оболочке в области внутреннего зева шейки матки перед предлежащей частью плода. Эти сосуды не защищены вартоновым студнем или тканью плаценты, в связи с чем могут легко повреждаться или подвергать-ся компрессии на любом сроке беременности, хотя подавляющее большинство фатальных осложнений развивается во время нача-ла родовой деятельности. VP может развиваться как результат обо-лочечного прикрепления пуповины, когда место выхода пуповины располагается за пределами плацентарной ткани и ее сосуды в ам-ниотической оболочке пересекают нижний сегмент матки (тип I) или в ситуации, когда сосуды плодового происхождения проходят меж-ду дополнительными долями плаценты (тип II) [1]. Непосредствен-ной причиной высокой перинатальной смертности при VP является кровотечение из сосудов, располагающихся в области внутреннего зева, в случае их повреждения при разрыве амниотических оболо-чек, что приводит к быстрой и значительной кровопотере у плода с трагическим исходом [1, 2]. Кроме того, предлежащая часть мо-жет вызывать компрессию незащищенных сосудов, проходящих в амниотической мембране, приводя к асфиксии и интранатальной гибели плода [3]. Частота VP составляет примерно 1 на 2500 родов, хотя, по мнению большинства авторов, распространенность, скорее всего, выше, так как при отсутствии симптомов при беременности это состояние может быть не выявлено во время родоразрешения и не отражено в статистике стационаров [1, 2]. В случае использо-вания вспомогательных репродуктивных технологий VP встреча-ется достоверно чаще-до 1 случая на 300 беременностей [1, 2, 4]. Цель исследования Проанализировать исходы беременности и особенности родоразрешения у беременных с VP. Материалы и методы Был проведен ретроспективный анализ исходов беременности у 17 пациенток с VP, родоразрешенных в СПбГБУЗ «Родильный дом 17» в 2014-2017 годах. Диагноз VP устанавливался при выявлении сосудов плодового происхождения, расположенных в области вну-треннего зева шейки матки, при трансвагинальном сканировании при применении цветного допплеровского картирования при сро-ке беременности более 18 недель. После установления диагноза VP всех пациенток наблюдали в динамике каждые 2 недели с обя-зательной трансвагинальной оценкой длины шейки матки для ис-ключения риска развития преждевременных родов. Родоразреше-ние путем операции кесарева сечения планировали при достиже-нии срока беременности более 32 недель после проведения кур-са антенатальной профилактики респираторного дистресс-синдро-СПбГБУЗ «Родильный дом № 17», Санкт-Петербург, Россия; 2 Северо-Западный государственный медицинский университет им. И.И. Мечникова, Санкт-Петербург, Россия; 3 Первый Санкт-Петербургский государственный медицинский университет им. акад. И.П. Павлова, Санкт-Петербург, Россия; 4 Санкт-Петербургский государственный педиатрический медицинский университет, Санкт-Петербург, Россия; 5 Санкт-Петербургский государственный университет, Санкт-Петербург, Россия ма плода путем внутримышечного введения 24 мг дексаметазона в течение 48 часов. Во время кесарева сечения выбор доступа в по-лость матки осуществлялся с помощью интраоперационного уль-тразвукового исследования с целью профилактики повреждения сосудов плодового происхождения, расположенных в области ниж-него сегмента, и снижения возможной кровопотери у плода. При отсутствии технических условий для безопасного вскрытия поло-сти матки в нижнем сегменте выполнялось донно-корпоральное кесарево сечение. Диагноз VP после родоразрешения подтверж-дали при визуальной оценке последа. Результаты и их обсуждение В исследование были включены 17 пациенток, родоразрешенных в СПбГБУЗ «Родильный дом 17» в 2014-2017 годах. Средний возраст пациенток составил 27 лет. В группу исследования вошли 11 (64,7%) первородящих и 6 (35,3%) повторнородящих. При оценке факторов риска низкая плацентация и краевое предлежание плаценты име-ли место у 7 (41,2%) пациенток, многоплодие у 5 (29,4%) и беремен-ность, полученная в результате вспомогательных репродуктивных технологий, у 2 (11,8 %) пациенток. В исследуемой группе средний срок установления диагноза VP составил 28 недель 3 дня. Средний срок родоразрешения-35 не-дель 2 дня. Было отмечено преобладание I типа VP-15 (88,2%) слу-чаев над II типом-2 (11,8%) случая. Все пациентки были родоразрешены путем операции кесарева сечения. В 9 (52,9%) случаях родоразрешение было в плановом по-рядке, в 8 (47,1%) случаях в экстренном. Экстренными показаниями в половине случаев было развитие родовой деятельности, в поло-вине случаев-преждевременное излитие околоплодных вод. При выполнении кесарева сечения в 6 (35,3%) случаях применялось ин-траоперационное УЗИ. Учитывая особенности ангиоархитектоники плаценты и предлежащих сосудов у 3 (17,6%) пациенток было выпол-нено донно-корпоральное, у 14 (82,4%) пациенток-кесарево сече-ние в нижнем сегменте матки. Средняя интраоперационная крово-потеря составила 520 мл. В одном случае, учитывая краевое пред-лежание плаценты, была выполнена двустороння перевязка восхо-дящих ветвей маточных артерий. Все новорожденные родоразрешены с оценкой по шкале Апгар более 7/8 баллов, в процессе динамического наблюдения ни одному ребенку не потребовалась гемотрансфузия в послеродовом периоде. Средний вес новорожденных составил 2487,7 г. Средняя оценка по шкале Апгар составила 7,8/8,8 баллов. Перевод в детскую больницу потребовался 9 (40,9%) детям, при этом все они были родоразреше-ны по экстренным показаниям. Показанием к продолжению стаци-онарного наблюдения послужил малый вес при рождении (второй этап выхаживания). 11 (50%) новорожденным не потребовалось на-хождение в палате интенсивной терапии.
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.
Décrire l’étiologie du vasa praevia et en décrire les facteurs de risque et les pathologies connexes; identifier les diverses présentations cliniques du vasa praevia; décrire les outils échographiques utilisés pour le diagnostic; et décrire la prise en charge du vasa praevia.
VASA PREVIA: THE CASE FOR ROUTINE SCREENING - Volume 24 Issue 4 - ANDREW ATKINSON, YINKA OYELESE
Velamentous insertion of the cord is defined as insertion of the umbilical cord into membranes before it enters the placenta. It occurs in 1% of singleton pregnancies. Vasa praevia occurs when the amniotic membrane with the velamentous vessels covers the cervical os. Its incidence is 1/2000 to 1/3000 but when it happens prenatal mortality is between 30%-100% from rupture of vessels and fetal exsanguination. Prenatal diagnosis and early delivery by Caesarean section at 36 weeks improve fetal outcome.
The placenta is essential for fetal growth and development. Ultrasound and Doppler are still the standard methods of placenta
investigation, but some pathologies such as placenta increta and infarction are better seen in magnetic resonance imaging
(MRI). Due to the larger field of view and multiplanar capabilities, MRI has advantages especially in advanced gestational
ages. The MRI appearance of the placenta can provide essential information about underlying pathologies contributing to fetal
problems such as intrauterine growth restriction (IUGR) and may be helpful for making management decisions or in monitoring
the severity of placental pathologies.
Vasa previa is an uncommon obstetric complication in which aberrant vessels coming from the placenta or the umbilical cord cross over the internal cervical os, thus appearing immediately before the foetal presentation. If it is not diagnosed before the onset of labour or rupture of membranes, the perinatal outcome is general very poor. We report a case of vasa previa which was prenatally diagnosed by ultrasound in a woman presenting with antepartum bleeding and a low-lying bilobular placenta in the third trimester. The aetiology and clinical management of this condition are discussed.
The perinatal mortality rate of vasa previa is high if it is not prenatally diagnosed. In this report, a case of vasa previa
diagnosed prenatally is presented. Antepartum hemorrhage at 24weeks of gestation prompted a close investigation of the uterine
cervix, internal os, and placenta. We detected a low-lying bilobed placenta with umbilical cord insertion in the lower uterine
segment. Furthermore, one of the connecting vessels of the bilobed placenta passed directly above the internal os. Vasa previa
was suspected and confirmed with color Doppler and MRI. The fetus was delivered uneventfully by planned Cesarean section at
38weeks of gestation. It should be considered that placenta previa (including low-lying placenta), bilobed placenta, and
umbilical cord insertion in the lower uterine segment are associated with high risk of vasa previa. Ultrasound screening for
cord insertion and placenta around the internal os enables efficient and certain detection of vasa previa.
KeywordsVasa previa-Lobed placenta-Transvaginal ultrasound
We report a case of a pregnant woman diagnosed as having vasa previa by magnetic resonance imaging (MRI). A parous woman was referred to our hospital at 31 weeks of gestation due to suspicion of placenta previa. Transvaginal ultrasound examination together with the Doppler techniques showed a fetal vessel on a lesion of low and high mixed echogenecities over the internal os, but could not confirm whether it was placental tissue or not. MRI demonstrated that it was not placenta but a hemorrhage between bilobed placentas and that the vessel was running over the internal os freely from the placenta. At 34 weeks of gestation, emergency cesarean section was performed due to increasing vaginal bleeding. MRI should be useful in the diagnosis of vasa previa when the relation between the position of the placenta and that of suspicious vessels cannot be adequately evaluated by ultrasound.
Labour is one of the shortest yet most hazardous journeys humans take during their lifetime. Currently, our methods of identifying those fetuses at particular risk of compromise during labour are limited. Antepartum tests of placental reserve give little information about an individual fetus's ability to cope with passage through the birth canal and some might already have received a silent insult earlier in the pregnancy that places them at increased risk. In addition to the normal processes of labour, other, more unpredictable factors can act to place the fetus in acute danger.
Vasa previa is a rare condition (1/2000 to 1/5000) in which the rupture of membranes may result in fetal haemorrhage (Benckiser's haemorrhage). We report one unusual case of delayed Benckiser's haemorrhage 12 hours after rupture of membranes. We point out the risk situations in which prenatal diagnosis should particularly be sought: low-lying placenta at routine second trimester ultrasound screening, bilobate or succenturiate placenta, velamentous insertion of the umbilical cord, in vitro fertilization. A universal screening, as proposed by certain authors, is also discussed.
Vasa previa is a cause of sudden unanticipated fetal death, with a fetal mortality of 33-100%. Transvaginal sonography (TVS) and color Doppler may aid in making the diagnosis antenatally, allowing elective Cesarean delivery, thereby avoiding fetal death from exsanguination which would occur if the membranes were allowed to rupture in labor. Whilst it is not feasible to screen all pregnant women for vasa previa, antenatal examination with TVS and color Doppler of women at risk, specifically those with low-lying placentas, bi-lobed, multi-lobed and succenturiate-lobed placentas, multiple pregnancies and pregnancies resulting from in vitro fertilization may lead to antenatal diagnosis of the condition. We present the last three cases of vasa previa to have occurred in our institution, two of which were diagnosed antenatally using TVS and color Doppler. In all three cases, routine 20-week obstetric sonography revealed low-lying placentas; in only one of these did the placenta remain low at term. A low-lying placenta at 20 weeks may be a risk factor for vasa previa; we suggest that further studies be carried out to ascertain this. Judicious use of TVS and color Doppler in women considered at risk of vasa previa may help to reduce the mortality from this condition.
Unlabelled:
Vasa previa is a rarely reported condition in which the fetal blood vessels, unsupported by either the umbilical cord or placental tissue, traverse the fetal membranes of the lower segment of the uterus below the presenting part. The condition has a high fetal mortality due to fetal exsanguination resulting from fetal vessels tearing when the membranes rupture. Despite improvements in medical technology, vasa previa often remains unsuspected until this fatal fetal vessel rupture occurs. Significant reduction in the fetal mortality from this condition depends on a high index of suspicion leading to antenatal diagnosis, and elective delivery by cesarean. We believe transvaginal ultrasound in combination with color Doppler is the most effective tool in the antenatal diagnosis of vasa previa and should be utilized in patients at risk, specifically those with bilobed, succenturiate-lobed, and low-lying placentas, pregnancies resulting from in vitro fertilization, and multiple pregnancy. Where there has been antepartum or intrapartum hemorrhage, especially when associated with fetal heart irregularities, we also recommend a test to exclude fetal blood in the vaginal blood. Similarly, amnioscopy before amniotomy may help to diagnose this condition. Cesarean delivery is the method of delivery of choice, and aggressive resuscitation of the affected neonate may be life saving. With a high index of suspicion, antenatal diagnosis using transvaginal sonography in combination with color Doppler, elective delivery by cesarean, and aggressive resuscitation of the neonate where fetal vessel rupture has occurred, the mortality from this complication may be considerably reduced.
Target audience:
Obstetricians & Gynecologists, Family Physicians.
Learning objectives:
After completion of this article, the reader will be able to identify the risk factors and associated conditions for vasa previa, to identify the various clinical presentations and management of vasa previa, and to be aware of the diagnostic tools available to make the antepartum diagnosis of vasa previa.
The surge in the development of fast magnetic resonance (MR) techniques has revolutionized our ability to image the pregnant patient and the fetus. Fast MR imaging techniques provide excellent resolution for imaging the maternal and fetal anatomies without the need for sedation. This article addresses the use of fast MR imaging techniques in the evaluation of the pregnant patient for adnexal masses, pelvimetry, hydroureteronephrosis of pregnancy, and placenta accreta. In addition, fetal anomalies for which MR imaging has proved useful, such as ventriculomegaly, arachnoid cysts, and abdominal masses, are described.
To describe the prenatal ultrasonographic diagnosis, natural evolution, and clinical outcomes of vasa previa in a large population at a single institution.
We attempted to view the internal cervical os of 93,874 women with second- and third-trimester pregnancies during an 8-year period. Echogenic parallel or circular lines near the cervix, seen by gray-scale ultrasonography, raised the possibility of vasa previa. Diagnosis was confirmed by Doppler and endovaginal studies if aberrant vessels over the internal cervical os were suspected. Abnormal placental morphology and velamentous cord insertion were documented if they were identified during prenatal scans. Ultrasonographic findings were correlated with clinical courses, perinatal outcomes, and placental pathology examinations.
Eighteen cases of vasa previa were suspected at a mean (+/- standard deviation) gestational age of 26.0 +/- 6.3 weeks; the earliest diagnosis was at 15.6 weeks' gestation. Eight of those cases initially showed placental edge over the internal os and later developed vasa previa after the placenta "receded" from the cervix. Six women had mild vaginal bleeding at a mean gestational age of 31.3 weeks. Three women had normal late third-trimester scans and were allowed to have uncomplicated vaginal deliveries. The remaining subjects delivered by cesarean. There were two deaths (one fetal and one neonatal), and minor preterm complications slightly prolonged infant hospitalizations. One set of preterm twins needed neonatal transfusions. Pathology findings included ten cases of velamentous insertion and three cases each of bilobed placentas, succenturiate lobes, and marginal cord insertion.
Vasa previa was detected in asymptomatic women as early as the second trimester. Perinatal outcome was generally favorable, although several infants had slightly extended newborn nursery admissions due to mild complications of prematurity.
To assess the specificity of sonographic diagnosis of vasa previa and pregnancy outcome in sonographically diagnosed cases.
We prospectively collected cases of vasa previa diagnosed by color Doppler sonography. Delivery by elective Cesarean section after demonstration of fetal pulmonary maturity and prior to the onset of labor was recommended unless obstetric complications supervened. Data regarding maternal obstetric courses and newborn status were collected.
Eleven cases of vasa previa without placenta previa were diagnosed among 33 208 women over an 8-year period. Ten patients had confirmation of the diagnosis by the delivering obstetrician and/or placental examination, giving a specificity of diagnosis of 91%. Among the 10 patients with confirmed vasa previa, two were delivered at 31.5 and 35.5 weeks' gestation prior to demonstration of lung maturity, and the remainder were delivered at 34-37.5 weeks, after lung maturity. All infants had normal Apgar scores and survived. One baby had Scimitar syndrome, which was not suspected from sonography.
The specificity of sonographic diagnosis of vasa previa at our center was 91%. Antenatal diagnosis permitted us to prevent the catastrophic outcomes commonly associated with vasa previa.