E. Clinodactyly-hypoplasia of the 5th finger middle phalanx creates an inward curvature (arrow). F. "Sandal-gap" (arrow).
0.5 percent of pregnancies and most commonly represents small amounts of swallowed blood, frequently in the setting of maternal serum AFP level elevation. Although typically associated with normal outcomes, it raises the risk for Down syndrome approximately sixfold. Echogenic bowel has also been associated with fetal cytomegalovirus infection and cystic ibrosisrepresenting inspissated meconium in the latter.
The femur and humerus are slightly shorter in Down syndrome fetuses. The femur is considered "short" for Down syndrome screening if it measures below the 2.5th percentile or is shortened to :;90 percent of that expected based on the measured biparietal diameter (American College of Obstetricians and Gynecologists, 2016c; Benacerraf, 1987). As an isolated finding in an otherwise low-risk pregnancy, it is generally not considered to pose great enough risk to warrant counseling modification. Similarly, a humerus shortened to :;89 percent of that expected, based on a given biparietal diameter, has also been associated with an elevated risk for Down syndrome.
If an isolated minor marker is identified in a woman who has not yet received aneuploidy screening, screening should be ofered, and a minor marker is considered an indication to ofer cell-free DNA screening (American College of Obstetricians and Gynecologists, 2016c). If cell-free DNA screening has already been performed, the association between isolated minor markers and aneuploidy risk is no longer considered relevant (Reddy, 2014). And, if the cell-free DNA screening result is negative, the fetal aneuploidy risk is not modified by the marker. Conversely, if a cell-free DNA screening result is positive, the absence of minor markers is not considered reassuring.
Unlike second-trimester soft signs, which may be readily visible during standard sonography, irst-trimester findings associated with aneuploidy require specialized training. The fetal NT measurement has gained widespread use for aneuploidy screening. Other irst-trimester sonographic findings are not routinely used in the United States but may be available in specialized centers. he Perinatal Quality Foundation's Nuchal Translucency Quality Review Program ofers an education program in irsttrimester nasal bone assessment (see Fig. 14-2). he Fetal Medicine Foundation also provides online instruction and certification in first-trimester assessment of nasal bone, ductus venosus low, and tricuspid flow.
Other benefits of irst-trimester sonography in women who elect aneuploidy screening include accurate assessment of gestational age and early detection of multifetal gestation or fetal demise. As discussed in Chapter 10 (p. 186), first-trimester sonography may identiy selected major anomalies associated with aneuploidy, such as cystic hygroma.