Adjunct to external cephalic version
Assessment for findings that raise the aneuploidy risk
Follow-up evaluation of a fetal anomaly
History of congenital anomaly in prior pregnancy
Adapted from the American Institute of Ultrasound in Medicine,l201l3a.
College of Obstetricians and Gynecologists, 2016). This time interval permits accurate assessment of gestational age, fetal anatomy, placental location, and cervical length. Recognizing that the gestational age at which abnormalities are identified may afect pregnancy management options, providers may opt to perform the examination prior to 20 weeks. The many additional indications for second-and third-trimester sonography are listed in Table 10-5. The three examination types are standard, specialized-which includes targeted sonography, and limited.
The standard sonogram includes evaluation of fetal number and presentation, cardiac activity, amnionic fluid volume, placental position, fetal biometry, and fetal anatomy (American Institute of Ultrasound in Medicine, 2013b). When technically feasible, the maternal cervix and adnexa are examined as clinically appropriate. Components are found in Table 10-3, and the fetal anatomical structures that should be evaluated are listed in Table 10-6. With twins or other multiples, documentation also includes the number of chorions and amnions, comparison of fetal sizes, estimation of amnionic luid volume within each sac, and fetal sex determination (Chap. 45, p. 868).
he targeted sonogram is a type of specialized examination. It is performed when the risk for a fetal anatomical or genetic abnor mality is elevated because of history, screening test result, or abnor mal inding during standard examination (Table 10-7) . Targeted sonograms include a detailed anatomical survey, the components of which are shown in Table 10-6. Because it carries the CPT code 76811, this sonogram is colloquilly called the "76811 examina tion." It is intended to be indication-driven and should not be repeated later in the absence of an extenuating circumstance.
have expertise in fetal imaging, through both training and ongo ing experience (Wax, 2014). For many of the targeted examina tion components, the physician determines on a case-by-case basis whether assessment is needed (American College of Obstetricians and Gynecologists, 2016). Other types of specilized examinations include fetal echocardiography, Doppler evaluation, and the bio physical proile, which is described in Chapter 17 (p. 337).
A limited sonogram is performed to address a speciic clini cal question. Examples include evaluation of fetal presentation, viability, amnionic luid volume, or placental location. In the absence of an emergency, a limited examination is only per formed if a standard sonogram has already been completed.
Otherwise, provided that the gestational age is at least 18 weeks, a standard sonogram is recommended.
With current advances in imaging technology, approximately 50 percent of major fetal abnormalities overall are detected with standard sonography (Rydberg, 2017). he sensitivity of sonography for detecting fetal anomalies varies according to factors such as gestational age, maternal habitus, fetal position, equipment features, examination type, operator skill, and the speciic abnormality in question. For example, maternal obesity has been associated with a 20-percent reduction in the anomaly detection rate (Dashe, 2009).
Detection also varies considerably according to the abnormality.