الفهرس 
Pathology of Placental AbnormalitiesOnly 14 pages are availabe for public view
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Abstract
The placenta, commonly called the afterbirth, is an organ that develops in the uterus during pregnancy. It is a unique characteristic of the higher mammals. The placenta draws nourishment and oxygen, which it supplies to the fetus, from the maternal circulation. In turn, the placenta receives the wastes of fetal metabolism and discharges them into the maternal circulation for disposal. It also acts as an endocrine gland, producing estrogen, progesterone and gonadotrophin. Shortly after delivery of the fetus the placenta is forced out by contractions of the uterus.
Placental abnormalities include abnormalities of location, implantation, thickness as well as anomalous shape, abnormal placental calcifications, placental tumors and placenta in multiple gestations.
The placenta can be effectively studied by antenatal ultrasound. Valuable information regarding placental configuration, location, maturity, pathology and maturation irregularities can be assessed. It is recognized that the anatomic components of the placenta are discernible from as early as the seventh to eighth weeks of gestation. By the 12th week of pregnancy, sonography can determine the position of the placenta and identify specific components of the placenta. The placental location, appearance and relationship to the internal cervical os should be recorded. The umbilical cord should be imaged, and the number of vessels in the cord should be evaluated when possible.
As for the assessment of placental vascularization, 3D power Doppler allows the evaluation of the placental vascular tree architecture, and of its vascular indices. The method apparently can show the villous vessels of the first, second and third order, with a higher percentage of vascularization than the two-dimensional Doppler.
The last two decades have witnessed unprecedented developments of new imaging systems making use of 3D visualization. These new technologies have revolutionized diagnostic imaging, as they provide the clinician with information about the interior of the human body never before available. Ultrasound imaging is an important cost-effective technique used routinely in the management of a number of diseases. However, 2D viewing of 3D anatomy, using conventional ultrasound, limits our ability to quantify and visualize the anatomy and guide therapy, because multiple 2D images must be integrated mentally. This practice is inefficient, and leads to variability and incorrect diagnoses. Also, since the 2D ultrasound image represents a thin plane at an arbitrary angle in the body, reproduction of this plane at a later time is difficult. Over the past 2 decades, investigators have addressed these limitations by developing 3D ultrasound and power Doppler techniques. The 2D images are digitized and then reconstructed in real-time into a 3D image, which can be viewed and manipulated interactively.
In Placental evaluation, 3-D ultrasonography enables visualization of placental changes, including calcifications, placental ”lakes,” indentations of the chorionic plate, and changes in gray-scale echogenicity. 3 D display also helps to identify abnormal position, abruption, hematoma, and accreta. This capability is especially helpful in evaluating membranes and other anatomical relationships in twin gestations.
Some diagnostic procedures as well as therapy and surgery planning require accurate volume measurements in which 3D ultrasound and power Doppler play an important role. The use of 2D ultrasound for measurement of organ or lesion volume is variable and at times inaccurate.