45 Ultrasound before 11 weeks’ gestation is not typically regarded as a routine part of pregnancy assessment. The embryonic stage, ending at 10 weeks’ gestation, is a time of very rapid change in the small, developing conceptus. All stated gestational ages are according to last menstrual period dating.ĮARLY FIRST TRIMESTER SCAN (5 TO 10 WEEKS’ GESTATION) Three-dimensional (3D) ultrasound can be a useful adjunct to 2D ultrasound in select circumstances and will be discussed in Chapter 2. Each image used in this chapter was obtained using two-dimensional (2D) ultrasound. This chapter deals with normal fetal anatomy however, frequent references to anomalies are made to underscore the pertinence of a good anatomic evaluation. In addition to describing the basic components of an obstetrical ultrasound examination in this chapter, we also present extended views that improve the quality of the examination and the detection of pregnancy-related problems. However, many experts in the field advocate the use of additional views to improve diagnostic performance. 3 – 7 Guidelines typically describe the essential components of an obstetric ultrasound examination. These include organizations such as the American College of Obstetricians and Gynecologists (ACOG), American Institute of Ultrasound in Medicine (AIUM), Australasian Society of Ultrasound in Medicine (ASUM), National Health Service (NHS) in the United Kingdom, and the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) ( Table 1.3). Several national and international bodies have described standards for imaging in the first, second, and third trimester of pregnancy. NRCP report 140.Įffective prenatal diagnosis relies on a high standard of imaging. Bethesda, MD: National Council on Radiation Protection and Measurements 2002. Exposure Criteria for Medical Ultrasound, II: Criteria Based on All Known Mechanisms. National Council on Radiation Protection and Measurements. American Institute of Ultrasound in Medicine consensus report on potential bioeffects of diagnostic ultrasound. ■ When MI is above 0.5 or the TI is above 1.0, the NCRP recommends that the risks of ultrasound be weighed against the benefitsįrom Fowlkes JB Bioeffects Committee of the American Institute of Ultrasound in Medicine. ■ The temperature of the fetus should not safely rise more than 0.5☌ above its normal temperature ■ There is no epidemiologic support for a causal relationship between diagnostic ultrasound during pregnancy and adverse biologic effects to the fetus observed for outputs under a spatial-peak temporal-average intensity of 94 mW/cm 2 ■ Apply the ALARA principle if the tissues to be exposed contain stabilized gas bodies (lung) and the MI exceeds 0.4 ■ Ultrasound exposures that elevate fetal temperature by 4☌ above normal for 5 min or more have the potential to induce severe developmental defects Selected Safety Recommendations for Diagnostic Ultrasound

Images for fetal echo cardiograph views