A case of placenta accreta complicated by severe IUGR and maternal coagulopathy

Animal models of the placenta accreta spectrum: current status and further perspectives

Placenta accreta spectrum disorder (PAS) is a kind of disease of placentation defined as abnormal trophoblast invasion of part or all of the placenta into the myometrium, even penetrating the uterus. Decidual deficiency, abnormal vascular remodeling in the maternal-fetal interface, and excessive invasion by extravillous trophoblast (EVT) cells contribute to its onset. However, the mechanisms and signaling pathways underlying such phenotypes are not fully understood, partly due to the lack of suitable experimental animal models. Appropriate animal models will facilitate the comprehensive and systematic elucidation of the pathogenesis of PAS. Due to the remarkably similar functional placental villous units and hemochorial placentation to humans, the current animal models of PAS are based on mice. There are various mouse models induced by uterine surgery to simulate different phenotypes of PAS, such as excessive invasion of EVT or immune disturbance at the maternal-fetal interface, which could define the pathological mechanism of PAS from the perspective of the "soil." Additionally, genetically modified mouse models could be used to study PAS, which is helpful to exploring the pathogenesis of PAS from the perspectives of both "soil" and "seed," respectively. This review details early placental development in mice, with a focus on the approaches of PAS modeling. Additionally, the strengths, limitations and the applicability of each strategy and further perspectives are summarized to provide the theoretical foundation for researchers to select appropriate animal models for various research purposes. This will help better determine the pathogenesis of PAS and even promote possible therapy.

Indicated preterm birth for placenta accreta

The purpose of this article is to review the risks and benefits of scheduled preterm delivery in patients with placenta accreta, increta, and percreta and to provide guidance regarding timing of delivery in such cases. Relevant documents for this opinion were identified through a search of the English literature for publications, including one or more of the keywords "accreta" or "increta" or "percreta" and "preterm" and "delivery time" by the use of PubMed (U.S. National Library Of Medicine, January 1990-January 2010), with results limited to studies involving humans. Additional information was obtained from references identified from within selected articles, from additional review articles, and from guidelines by organizations, including the American College of Obstetricians & Gynecologists. Each included article was evaluated according to study design and quality in accordance with scheme outlined by the U.S. Preventative Services Task Force, and final recommendations are provided based on the level of published evidence. On the basis of this search, we found that abnormal placentation, encompassing placenta accreta, increta, and percreta, is increasingly common. We also found that randomized controlled trials and well-controlled observational studies that can be used to define best practice in delivery time are lacking. Optimal delivery time must be determined from available case series, retrospective reviews and decision analysis studies. Given the best-available evidence, optimal time for delivery is believed to be between 34 and 35 weeks in most cases.

Role of three-dimensional power Doppler in the antenatal diagnosis of placenta accreta: comparison with gray-scale and color Doppler techniques

OBJECTIVE

To assess the role of three-dimensional (3D) power Doppler in the antenatal diagnosis of placenta accreta and compare its diagnostic performance with gray-scale and color Doppler ultrasonography.

METHODS

One hundred and seventy pregnant women with persistent placenta previa totalis (after 28 weeks' gestation) were prospectively enrolled into this study. Gray-scale transabdominal ultrasound examination was performed to detect loss of the subendometrial echolucent zone and other abnormalities suggestive of placenta accreta. Color flow mapping was used to scan the whole placenta to detect any newly formed vessels at the serosa-bladder border or the presence of abnormal lacunae. Finally a targeted examination of angioarchitecture in the basal and lateral views of the placenta was carried out using 3D power Doppler. The ultrasound findings were analyzed with reference to the final diagnosis made during Cesarean delivery.

RESULTS

Placenta accreta and its variants (including increta and percreta) were confirmed in 39 patients at the time of Cesarean delivery. Based on receiver-operating characteristics analysis, 'numerous coherent vessels' visualized using 3D power Doppler in the basal view was the best single criterion for the diagnosis of placenta accreta, with a sensitivity of 97% and a specificity of 92%. If we considered the presence of at least one criterion to be diagnostic when using each ultrasound technique, then 3D power Doppler would have the best positive predictive value (76%), followed by gray-scale (51%) and color Doppler (47%). The majority of patients with placenta accreta showed multiple characteristic features on ultrasound imaging. In contrast, those patients with a false-positive diagnosis (i.e. the final diagnosis was placenta previa alone) tended to show isolated ultrasound markers of the condition.

CONCLUSION

3D power Doppler may be useful as a complementary technique for the antenatal diagnosis or exclusion of placenta accreta.