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INTRODUCTION

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Definitions

  1. Association: refers to a nonrandom occurrence in 2 or more individuals of multiple anomalies not known to represent a polytopic field defect, a sequence, or a syndrome.

  2. Deformation: refers to an abnormal form, shape, or position of part of the body caused by nondisruptive mechanical forces.

  3. Disruption: a morphologic defect of an organ, part of an organ, or a larger region of the body resulting from a breakdown or interference with an originally normal developmental process.

  4. Dysplasia: abnormal organization of cells into tissue(s) and its morphologic results.

  5. Malformation: morphologic defect of an organ, part of an organ, or a larger area of the body resulting from an intrinsically abnormal developmental process.

  6. Sequence: pattern of multiple anomalies derived from a single known or presumed prior anomaly or mechanical factor.

  7. Syndrome: pattern of multiple anomalies thought to be pathogenetically related and not known to represent a single sequence or a polytopic field defect.

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The detection of anatomic congenital anomalies is one of the goals of prenatal care.1 The information required for diagnosis and management of the obstetrical patient with a fetal congenital anomaly demands knowledge in a variety of disciplines, including embryology, anatomy, genetics, obstetrics, pediatric surgery, teratology, and, certainly, diagnostic imaging. Many health care professionals involved in diagnostic imaging have had limited exposure to the other fields. The purpose of this chapter is to introduce the reader to congenital anomalies, and provide an overview of the definition and magnitude of the problem and pathogenic mechanisms of gross congenital anomalies. The principles of prenatal diagnosis with ultrasound, the use of ultrasound as a screening tool for the detection of congenital anomalies, and the management options once a congenital anomaly has been detected are also discussed.

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FUNDAMENTAL CONCEPTS

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A congenital anomaly consists of a departure from the normal anatomic architecture of an organ or system. Anomalies may result from an intrinsically abnormal primordium or anlage of an organ, or from a normal primordium that is affected during development by extrinsic forces.2,3, and 4 Growing interest in prenatal development, coupled with the need for a uniform nomenclature to refer to errors in morphogenesis, led an international working group to propose a set of terms useful in the classification of anatomic congenital anomalies. Individual alterations of form or structure can therefore be classified as malformations, deformations, and disruptions. However, it should be stressed that it is not always possible to assign an anomaly to a specific class. In fact, malformations, deformations, and disruptions may overlap (see section on sequences).

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Malformation

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A malformation is a morphologic defect of an organ, part of an organ, or a larger area of the body resulting from an intrinsically abnormal developmental process. The term intrinsically abnormal developmental process refers to an abnormality in the primordium (anlage) of the organ. This abnormality may ...

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