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Beginning in the 1960s, medical ultrasound offered an alternative to x-ray to evaluate the developing fetus. With the sequential discoveries of A-mode, M-mode, B-mode (amplitude, motion, and brightness, respectively), pulsed-wave, and color Doppler, imaging quality and applications have developed and expanded to current modalities of 2-dimentional and 3-dimensional ultrasound with capacity to store volumes for later manipulation.1 Ultrasound and obstetric imaging has evolved from the standpoint of image quality and design. Now pocket-sized, hand-held devices are available to the end-user, and many medical schools include ultrasound and ultrasound simulation programs in first-year curriculum.
Safety is a fundamental element of all imaging modalities in obstetrics and practitioners need to be cognizant of fetal exposure and are responsible for machine output. When performing medically indicated examinations using the ALARA (As Low As Reasonably Achievable) principle, ultrasound has a high safety profile, is noninvasive, and is relatively inexpensive. Adjunctive imaging utilized in obstetrics includes magnetic resonance imaging and computed tomography.
Imaging begins with a thorough evaluation of the maternal uterus and adnexa. Cervical pregnancies, a rare type of ectopic pregnancy, can be diagnosed with early sonography; cesarean scar pregnancies are increasing in number paralleling the cesarean delivery rate (32% in the United States) Also coincident with the increased cesarean delivery rate is the occurrence of morbidly adherent placentation, which if goes unnoticed during an ultrasound examination, may lead to catastrophic hemorrhage before or at the time of delivery.
Cervical length evaluation is another aspect of imaging important to the practitioner. It allows the clinician to assess risk for preterm delivery and identify women with suspected cervical weakness.2 According to recent WHO statistics, approximately 15 million babies every year (>1 in 10) are born before 37 completed weeks (preterm),3 and in the United States, about 12% of all live births occur before term.4 Children born preterm face disabilities and almost 1 million children per year die from associated complications.3
Anatomic obstetric imaging is extending from the second trimester to the first trimester with the potential to detect one-half of major fetal anomalies by 14 weeks.5 Genetic screening and first trimester anatomic imaging yield earlier diagnostic results, and in the morbidly obese gravida, may allow for improved image acquisition. Fetal neurosonography of the developing fetal brain allows for longitudinal evaluation and can compare developmental milestones and anatomy over the course of pregnancy. Evaluation of the fetal heart and first trimester fetal echocardiography has immerged as early diagnostic tools. Modalities for structural and functional cardiac interpretation and evaluation are now available. Aside from aid in timing of delivery, the assessment of arterial and venous Dopplers of the at-risk fetus is important for understanding the physiology and risk of perinatal morbidity and mortality.
This symposium addresses advances in ultrasound and obstetric imaging that are at the forefront of care. The importance of safety cannot be overemphasized. Authors highlight a contemporary and practical perspective of available obstetric imaging to the end-user offering a balanced approach. I thank the authors for their willingness to devote the time and effort required to prepare chapters with the accompanying diagnostic images as well as their expertise in the field to update clinicians in new innovative ultrasound techniques.
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