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The introduction and the continuing advances in fetal Doppler echocardiography have enhanced our understanding of the hemodynamic function of the fetal heart and extended our knowledge of the aberrations of this function in various cardiac disorders. The latter include congenital cardiac malformations, cardiac rhythm disturbances, and fetal heart failure. Many of these conditions in the context of Doppler sonography are discussed elsewhere in this text. It is apparent that the addition of the Doppler modality significantly enhances the diagnostic information that can be obtained from sonographic imaging of the fetal heart, and color and spectral Doppler echocardiography has now become an essential component of the fetal cardiac examination. In order to ensure the reliability of the technique it is imperative, however, that one should be thoroughly familiar with the instrumentation and rigorously trained in its application. When used appropriately, Doppler echocardiography remains a unique and powerful tool for fetal assessment in health and disease.

Recent years have witnessed significant progress in the technique of fetal echocardiography and perinatal management of fetal cardiac disease. Although 2D cardiac imaging remains the major tool for this evaluation, its diagnostic efficacy is significantly enhanced by the other ultrasound modalities. Specifically, spectral pulsed Doppler, 2D Doppler color flow mapping, and color M-mode provide essential tools for elucidating hemodynamic abnormalities associated with structural and functional congenital cardiac disease. This hemodynamic information plays a crucial role in enhancing the efficacy of investigating these complex problems. It is not surprising, therefore, that Doppler echocardiography now plays such a critical role in the diagnosis, treatment, and surveillance of fetal cardiac disorders. Future developments in this area will certainly encompass 3D Doppler flow evaluation, which has been addressed in Chaps. 7 and 34.

Development of 4D ultrasound represents a major advance in non-invasive diagnostice technology and its introduction in clinical practice has initiated a significant paradigm shift in medical ultrasound imaging. Four-dimensional echocardiography allows a more comprehensive assessment of the fetal cardiac anatomy and hemodynamics than has been achievable in any of the current or legacy systems. It has the real potential of significantly expanding the scope of in utero diagnosis of congenital heart disease and other abnormalities of the fetal heart. This is a very new technology and there is a real dearth of investigations critically evaluating its promises and limitations in the fetal application. This is especially relevant for extending its use outside the domain of experts and enthusiasts. At present, traditional 2D B-mode and Doppler sonography will continue to be the standard of practice for fetal cardiac assessment with substantial supplemental assistance from the 4D echocardiography which, however, has the strong potential to become the mainstream approach in the future.

A large number of clinical conditions have been found that may lead to intrauterine cardiac failure. Pulsed and color Doppler techniques have improved our knowledge of fetal cardiovascular response to structural and functional heart diseases. Key features of developing fetal hear failure that may be seen include: 1. Valvular regurgitation 2. Altered velocities 3. Chamber dilatation 4. Fluid collections: ascites, edema, pericardial 5. Reverse flow: vena cava, umbilical pulsations. Doppler blood flow studies have enable investigators and clinicians to better understand the pathological processes involved in developing fetal heart failure and to plan appropriate treatments or interventions. We can expect that further study and experience with the use of Doppler blood flow studies will lead to increased improvement in perinatal morbidity and mortality.

Examination of the fetal circulation by Doppler techniques provides evidence of some of the mechanisms of adaptation and decompensation of the IUGR fetus in response to uteroplacental insufficiency. At present, the condition of IUGR fetuses can be accurately assessed by sequential studies of Doppler waveforms from various vascular areas. Therefore the optimal timing of delivery to prevent intrauterine injury may be guided by combining multivessel Doppler ultrasounds. Combining Doppler, composite biophysical profile, and/or computerized fetal heart rate analysis will provide significant early indication for action in the management of severe IUGR fetuses.

Treatment of preterm labor with nonsteroidal antiinflammatory agents can lead to acute, transient changes in the caliber of the fetal ductus arteriosus. These changes can be detected and quantitated using fetal echocardiography. This complication can be successfully managed with serial study of the fetus using Doppler techniques and may be indicated serially. The β-agonist sympathomimetic medications used to treat preterm labor, such as terbutaline, have an immediate effect on the fetal circulation and increase the heart rate and the inotropic state of the fetal myocardium. The future will see improved methods of fetal testing to assess the effects of both preterm labor and its treatment on the fetal circulation.

The color Doppler modality provides a valuable approach to the pathology of female reproductive organs. The results reported in the recent literature on three-dimensional color and/or power Doppler are indeed provocative and, not surprisingly, raise many new questions about the regulation of tumor angiogenesis, the density of tumor vessels, and the differences between vessel architecture in benign and malignant growths. Three-dimensional power Doppler depiction of tumor angiogenesis has many clinical implications, including early detection of ovarian and endometrial cancers. Improved detection and classiffication of tumor architecture after instillation of contrast agents might contribute to better diagnostic accuracy. Early detection of ovarian carcinoma is still the most attractive argument for conducting additional studies.