Approximately 30 percent of second-trimester fetuses with Down syndrome have a major malformation that can be identified sonographically (Hussamy, 2017; Vintzileos, 1995). As discussed in Chapter 14 (p. 286), when both major anomalies and minor aneuploidy markers are considered, an estimated 50 to 60 percent of Down syndrome pregnancies can be detected sonographically (American College of Obstetricians and Gynecologists, 2016d). Approximately half of liveborn neonates with Down syndrome are found to have cardiac defects, particularly ventricular septal defects and endocardial cushion defects (Figs. 10-29 and 10-30, p. 202) (Bergstrom, 2016; Freeman, 2008). Gastrointestinal abnormalities are identiied in 12 percent and include esophageal atresia, Hirschsprung disease, and duodenal atresia (Fig. 10-38, p. 207) (Bull, 2011).
Characteristic features of Down syndrome are shown in
Figure 13-4. Typical indings include brachycephaly; epicanthaI folds and up-slanting palpebral issures; Brushield spots, which are grayish spots on the periphery of the iris; a lat nasal bridge; and hypotonia. Infants often have loose skin at the nape of the neck, short ingers, a single palmar crease, hypoplasia of the middle phalanx of the fifth finger, and a prominent space or "sandal-toe gap" between the irst and second toes. Some of these indings are prenatal sonographic markers for Down syndrome, reviewed in Chapter 14 (p. 286).
Health problems common in children with Down syndrome include hearing loss in 75 percent, severe optical refractive
FIGURE 13-4 Trisomy 21-Down syndrome. A. Characteristic facial appearance. B. Redundant nuchal tissue. C. Single transverse palmar crease. (Used with permission from Dr. Charles P. Read and Dr. Lewis Waber.) errors in 50 percent, cataracts in 15 percent, obstructive sleep apnea in 60 percent, thyroid disease in 15 percent, and a higher incidence of leukemia (Bull, 2011). The degree of mental impairment is usually mild to moderate, with an average intelligence quotient (IQ) score of 35 to 70. Social skills in afected children are often higher than predicted by their IQ scores.
Data suggest that approximately 95 percent of liveborn infants with Down syndrome survive the irst year. The 10-year survival rate is at least 90 percent overall and is 99 percent if major malformations are absent (Rankin, 2012; Vendola, 2010). Several organizations ofer education and support for prospective parents faced with prenatal diagnosis of Down syndrome. These include the March of Dimes, National Down Syndrome Congress (ww.ndsccenter.org), and National Down Syndrome Society (ww.ndss.org).