Vasa previa, diagnóstico prenatal y manejo obstétrico / Vasa previa, prenatal diagnosis and management

Vasa previa ocurre cuando los vasos umbilicales no protegidos por el tejido placentario o cordón umbilical se sitúan en el segmento uterino inferior, delante de la presentación fetal a menos de 2 cm del orificio cervical interno. Los factores de riesgo son inserción velamentosa de cordón, placenta previa, placenta succenturiata y técnicas de reproducción asistida. El diagnóstico mediante ecografía transvaginal y Doppler color permite objetivar la presencia de vasos fetales por delante de la presentación fetal. El manejo incluye la maduración fetal con corticoides y cesárea electiva antes del parto. Describimos un caso clínico ocurrido en nuestro hospital

Vasa praevia is a condition in which the umbilical vessels, not supported by either the umbilical cord or placental tissue, cross the foetal membranes of the lower segment within 2 cm of the internal cervical os. The risk factors are velamentous insertion of the cord, placenta praevia, a bilobed and succenturiate placenta, and the use of assisted human reproductive techniques. The antenatal diagnosis by transvaginal ultrasound and colour Doppler can be used during the routine second trimester ultrasound in women with high risk. When the diagnosis is made in the antenatal period, the safest form of delivery is an elective caesarean with administration of corticosteroids prior to the onset of labour. A case diagnosed in our hospital is presented

Vasa previa: prenatal diagnosis and management.

PURPOSE OF REVIEW: Vasa previa is a rare disorder of placentation associated with a high rate of perinatal morbidity and mortality when undetected before delivery. We have evaluated the recent evidence for prenatal diagnosis and management of vasa previa. RECENT FINDINGS: Around 85% of cases of vasa previa have one or more identifiable risk factors including in-vitro fertilization, multiple gestations, bilobed, succenturiate or low-lying placentas, and velamentous cord insertion. The development of standardized prenatal targeted scanning protocols may improve perinatal outcomes. There is no clear consensus on the optimal surveillance strategy including the need for hospitalization, timing of corticosteroids administration and the value of transvaginal cervical length measurements. Outpatient management is possible if there is no evidence of cervical shortening on ultrasound and there are no symptoms of bleeding or uterine contractions. Recent national guidelines and expert reviews have recommended scheduled cesarean section of all asymptomatic women presenting with vasa previa between 34 and 36 weeks' gestation. SUMMARY: Prenatal diagnosis of vasa previa is pivotal to prevent intrapartum fetal death. Although there is insufficient evidence to support the universal mid-gestation ultrasound screening for vasa previa, recent evidence indicates the need for standardized prenatal targeted screening protocols of pregnancies at high-risk of vasa previa.

Vasa previa screening strategies: decision and cost-effectiveness analysis.

OBJECTIVE: To perform a decision and cost-effectiveness analysis comparing four screening strategies for the antenatal diagnosis of vasa previa in singleton pregnancies. METHODS: A decision-analytic model was constructed comparing vasa previa screening strategies. Published probabilities and costs were applied to four transvaginal screening scenarios that were carried out at the time of mid-trimester ultrasound: no screening, ultrasound-indicated screening, screening only pregnancies conceived by in-vitro fertilization (IVF) and universal screening. Ultrasound-indicated screening was defined as performing transvaginal ultrasound at the time of the routine anatomy ultrasound scan in response to one of the following sonographic findings associated with an increased risk of vasa previa: low-lying placenta, marginal or velamentous cord insertion or bilobed or succenturiate lobed placenta. The primary outcome was cost per quality-adjusted life year (QALY) in US$. The analysis was performed from a healthcare system perspective with a willingness-to-pay threshold of $100 000 per QALY selected. One-way and multivariate sensitivity analysis (Monte-Carlo simulation) was performed. RESULTS: This decision-analytic model demonstrated that screening pregnancies conceived by IVF was the most cost-effective strategy, with an incremental cost effectiveness ratio (ICER) of $29186.50/QALY. Ultrasound-indicated screening was the second most cost-effective, with an ICER of $56096.77/QALY. These data were robust to all one-way and multivariate sensitivity analyses performed. CONCLUSIONS: Within the baseline assumptions, transvaginal ultrasound screening for vasa previa appears to be most cost-effective when performed among IVF pregnancies. However, both IVF and ultrasound-indicated screening strategies fall within contemporary willingness-to-pay thresholds, suggesting that both strategies may be appropriate to apply in clinical practice. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Analysis of the ultrasonographic findings predictive of vasa previa.

OBJECTIVES: To clarify the ultrasonographic findings indicative of prenatal vasa previa. METHODS: The variables associated with placental and umbilical cord abnormalities were retrospectively analysed in cases with and without vasa previa. RESULTS: Consecutive subjects were divided into those with vasa previa (10) and controls (4682). Abnormal placental forms and placenta previa/low-lying placenta were associated with vasa previa [odds ratio (OR) 21.9 and 28.0]. While the frequency of velamentous cord insertion was 1.6% in the controls, it was 90% in the cases with vasa previa (OR 552). In addition, low cord insertions in the uterus were observed in 90% of the patients with vasa previa and only in 0.4% of the controls (OR 2470). Descending cords were also frequently observed in patients with vasa previa (OR 89.8). Finally, a multivariable regression analysis demonstrated an OR of 65.1 (95% confidence interval (CI) 5.8-733) for velamentous cord insertion and an OR of 344.7 (95% CI 31-3838) for low cord insertion with regard to the risk of vasa previa. CONCLUSION: Our results suggest that confirmation of the placental cord insertion, including not only velamentous cord insertion but also the cords located on the lower uterine segment, is the best way to detect vasa previa.