Trisomy 21, also known as Down syndrome, is one of the most common chromosomal syndromes, occurring in 1 in 600 to 800 live births (Gabbe, Simpson, & Niebyl, 2007). It affects all races and economic levels equally. Down syndrome often results from having an extra chromosome (usually chromosome 21) and is called trisomy 21 because it was first identified with this chromosome. Occasionally, the extra chromosome 21 is attached to another chromosome in the egg or sperm, which can create a translocation (an alteration in location). The translocation in either parent greatly increases the chances of having another child with Down syndrome. Mothers older than 35 years are at the greatest risk of having a Down syndrome newborn.

The American Academy of Pediatrics recommends screening of all pregnant women for Down syndrome in the first trimester of pregnancy. First trimester screening includes ultrasound assessment of the thickness of the fetal nuchal fold (called nuchal translucency). An ultrasound demonstrating absence of the nasal bone (Cicero, Avgidou, Rembouskos, et al., 2006) and a second trimester “quad test” involving blood testing of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (UE), and inhibin A (a placental hormone) are additional screening tests for Down syndrome. A low AFP or a high hCG and inhibin A, with a low UE, may indicate a high risk for Down syndrome for the developing fetus. A test of pregnancy-associated plasma protein A (PAPP-A) may also indicate a risk for Down syndrome. Positive tests in the first or second trimester may indicate a need for amniocentesis to confirm the diagnosis.

Characteristics of the Down syndrome newborn are most noted in the craniofacial features (Figure 16-1). The eyes have an upward slant because of an epicanthal fold, speckles known as Brushfield’s spots are seen in the iris, the nose is small with a wide nasal bridge, and the ears are low set. The tongue appears large and protrudes from the newborn’s mouth, fingers are short and broad, often there is an unusually wide space between the first two toes, and a single palmar crease (simian crease) may be present. Relatively common internal anomalies in trisomy 21 newborns include heart defects and duodenal atresia. Mental retardation is exhibited, with the mean IQ of approximately 50 (range: 25 to 70). Females are fertile; however, it is rare for males to be fertile.

Phenylketonuria (PKU) is an autosomal recessive inherited inborn error of phenylalanine metabolism that occurs in 1 in 15,000 live births (Trahms, 2008). It is caused by the faulty metabolism of phenylalanine, an amino acid that is essential to life and found in all protein foods. The hepatic enzyme phenylalanine hydrolase, which is required to convert phenylalanine into tyrosine, is missing. As a result, when the newborn ingests protein (found in milk and all protein foods), phenylketones accumulate in the blood and can rise as high as 20 times the normal level. Its byproduct, phenylpyruvic acid, appears in the urine within the first weeks of life. These phenylketones accumulate in the brain and cause irreversible brain damage, resulting in severe mental retardation. Early detection and treatment are essential because by the time the urine test is positive, brain damage has already occurred. The newborn appears normal at birth but begins to show delayed development at approximately 4 to 6 months of age. The newborn may show evidence of failure to thrive or have eczema or other skin conditions. Characteristically, these newborns have an unusual musty odor to their body and in their urine.

A diagnosis is made by the Guthrie test. Blood is obtained from a simple heel prick, and a few drops of capillary blood are placed on a filter paper and mailed to the laboratory for screening. It is recommended that the blood be obtained after 48 to 72 hours of life, preferably after ingestion of proteins, to reduce the possibility of false results. All states in the United States require that the test be performed in all newborns before they leave the nursery, but, because of early discharge, the test is often repeated after discharge. The newborn can be tested at home by a public health nurse or at the physician’s office or clinic. Confirmation of the diagnosis requires quantitative elevations of phenylalanine compound in both blood and urine. The nurse must stress to the mother the importance of the return visit of the newborn to the physician or clinic for the repeat testing.

Since the development of newborn screening for PKU, several women who had been diagnosed with PKU in the newborn period and then were treated with a phenylalanine-restricted diet have grown up not suffering the damages of untreated PKU. However, newborns born to women with PKU who do not follow the restricted diet during pregnancy have teratogenic effects if high concentrations of phenylalanine are circulating in the mother’s blood. Congenital heart defects, microcephaly, and mental retardation are the most commonly seen effects. Therefore, for these women, following dietary restrictions from conception (especially during embryonic development) is critical.

The newborn diagnosed with PKU is fed a special formula (Lofenalac) that has had the phenylalanine reduced or removed. Phenyl-Free is given to children, and Phenex-2 is given to adolescents. The goals of the diet are to provide enough essential proteins to support growth and development while maintaining phenylalanine blood levels between 2 and 10 mg/dL. A phenylalanine level less than 2 mg/dL may result in growth retardation, and a level greater than 10 mg/dL can result in significant brain damage. Levels are monitored throughout childhood.

A dietitian should be consulted for parental guidance and support in maintaining the dietary regimen. This attention is especially needed for the school-age child and the adolescent. The intake of most meat, dairy products, and diet drinks needs to be restricted, and protein intake is restricted to that required for basic growth. The milk substitute can be flavored with a fruit powder or a chocolate substitute, which can increase the child’s compliance. Aspartame, a sugar substitute, must be avoided. Genetic counseling is important for future family planning.

Galactosemia is an inborn error of metabolism that occurs in 1 in 53,000 live births (Tarini & Freed, 2007). The newborn has a deficiency of the enzyme necessary to convert galactose to glucose, resulting in an increased amount of galactose in the blood (galactosemia), liver, brain, kidney, and urine (galactosuria). An early diagnosis is important so that a milk substitute can be prescribed because galactose is present in milk. Galactosemia can be detected by measuring blood levels of galactose, and screening of all newborns is performed in most states across the United States. Failure to thrive, cataracts, jaundice, cirrhosis of the liver, sepsis, and mental retardation are manifestations of untreated cases. Therapy consists of eliminating galactose from the diet and providing lactose-free formula, such as Nutramigen. Because breast milk contains lactose, breastfeeding must be discontinued. Medications that contain lactose fillers as inactive ingredients also must be avoided. Parents and children often experience frustration and anxiety and must be educated and supported in following this dietary program.

Congenital hypothyroidism is the result of an inborn error of metabolism caused by a maternal iodine deficiency or the use of antithyroid drugs by the mother. It occurs 1 in 4000 live births (Palma-Sisto, 2004). Thyroxine (T₄) is measured from a drop of blood obtained from heel stick at 2 to 5 days of age. If not treated with thyroid replacement, the infant may develop hypothermia, poor feeding, lethargy, jaundice, and cretinism. The infant has a large protruding tongue, thick lips, and a generally dull appearance.

An important note is that one blood sample can be used to test all three metabolic disorders: PKU, galactosemia, and hypothyroidism. The screening test for hypothyroidism is mandated in all states across the United States and is often performed before discharge from the nursery. Early diagnosis and treatment are essential to maintain normal physical and mental growth and development.

Maple syrup urine disease is a disorder of amino acid metabolism in which the amino acids leucine, isoleucine, and valine cannot be metabolized because of missing enzymes. Elevated levels of leucine can cause cerebral edema and central nervous system (CNS) symptoms such as seizures. Body fluids have a sweet odor, similar to maple syrup. Some states require routine screening of all newborns for this condition (see Chapter 9). Nursing responsibilities include educating the family concerning strict dietary and exercise limitations throughout the infant’s lifetime.

The bilirubin level in newborns typically peaks between 3 and 5 days of age. Therefore, the early discharge of newborns requires follow-up observation within a few days. Conjugation of the bilirubin can be inhibited by a lack of bacteria in the intestines or a low level of glucuronyl transferase enzyme. The immature liver may also be slow to take up the bilirubin that flows to it. For these reasons, the liver may not be able to “clear” the bilirubin from the blood and excrete it from the body at a rapid rate. High levels of bilirubin in the blood can stain the basal nuclei of the brain, causing long-term neurologic problems. This condition is called kernicterus.

Because bilirubin conjugated by the liver is excreted by the body via the intestinal tract, the stimulation of meconium stool passage is an important part of the care plan. The initiation of early feedings enhances the passage of meconium and therefore plays an essential role in the management of hyperbilirubinemia. Colostrum, in breast milk, has a natural laxative effect, and therefore breastfeeding at least 10 times a day is recommended for the neonate. Glucose water supplements should be avoided because little bilirubin is excreted by the kidneys and decreased caloric intake is associated with decreased passage of stool, allowing for the reabsorption of bilirubin before it can be excreted. Although there is a factor in human milk that may increase reabsorption of bilirubin from the intestines, this rarely causes a significant rise in serum bilirubin. Some physicians may prefer to feed the infant bottled formula for a 12- to 24-hour period to avoid this small increase. The mother should be encouraged to pump milk from the breast during this short period to enable easy return to breastfeeding.

A major cause of hyperbilirubinemia is hemolytic disease, in which there is an excessive breakdown of RBCs of the newborn as a result of maternal antibodies passing through the placenta to the fetus in the uterus. Isoimmune hemolytic disease, also known as erythroblastosis fetalis, occurs when an Rh-negative mother is pregnant with an Rh-positive fetus and transplacental passage of maternal antibodies occurs. When maternal antibodies enter the fetal circulation, they destroy the fetal RBCs. The fetal system responds by increasing the RBC production with a marked increase in immature RBCs (erythroblasts). A high level of maternal antibodies may have developed during a previous pregnancy, abortion, amniocentesis, or abruptio placentae. A previous blood transfusion with Rh-positive blood would also cause the development of maternal antibodies. At birth, the newborn with hemolytic disease caused by Rh incompatibility has a positive direct Coombs’ test, which reveals the presence of antibody-coated (sensitized) Rh-positive RBCs in the newborn. The indirect Coombs’ test measures the amount of Rh-positive antibodies in the mother’s blood. If the mother prophylactically receives Rh_o(D) immune globulin (RhoGAM), maternal development of antibodies to Rh-positive blood greatly decreases (Figure 16-2). Pathologic jaundice, such as that caused by Rh incompatibility, is evident before the third day of life because the hemolysis begins before birth.

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