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Chapter 31: Child Psychiatry
Genetic Disorders
In many cases, genetic counseling depends on prenatal diag-
nosis. The diagnostic techniques used include amniocentesis
(transabdominal aspiration of fluid from the amniotic sac),
ultrasound examinations, x-ray studies, fetoscopy (direct visu-
alization of the fetus), fetal blood and skin sampling, chorionic
villus sampling, and
a
-fetoprotein screening. In about 2 percent
of women tested, the results are positive for some abnormal-
ity, including X-linked disorders, neural tube defects (detected
by high levels of
a
-fetoprotein), chromosomal disorders (e.g.,
trisomy 21), and various inborn errors of metabolism (e.g., Tay-
Sachs disease and lipoidoses). Figure 31.1-3 illustrates hyper-
telorism of the eyes.
Some diagnostic tests carry a risk; for instance, about 5 per-
cent of women who undergo fetoscopy miscarry. Amniocente-
sis, which is usually performed between the 14
th
and 16
th
weeks
of pregnancy, causes fetal damage or miscarriage in less than
1 percent of women tested. Fully 98 percent of all prenatal tests
in pregnant women reveal no abnormality in the fetus. Prenatal
testing is recommended for women older than 35 years of age
and for those with a family history of a congenital defect.
Parental reactions to birth defects can include feelings of
guilt, anxiety, or anger as their worst fears during the pregnancy
are realized. Some degree of depression over the loss of the
fantasized perfect child may be observed before the parents
develop more active coping strategies. Termination of a preg-
nancy because of a known or suspected birth defect is an option
chosen by some women.
Maternal Drug Use
Alcohol.
Alcohol use in pregnancy is a major cause of
serious physical and mental birth defects in children. Each
year, up to 40,000 babies are born with some degree of alco-
hol-related damage. The National Institute on Drug Abuse
(NIDA) reports that 19 percent of pregnant women used
alcohol during their pregnancy, the highest rate being among
white women.
Fetal alcohol syndrome (Fig. 31.1-4) affects about one third
of all infants born to alcoholic women. The syndrome is charac-
terized by growth retardation of prenatal origin (height, weight);
minor anomalies, including microphthalmia (small eyeballs),
short palpebral fissures, midface hypoplasia (underdevelop-
ment), a smooth or short philtrum, and a thin upper lip; and
central nervous system (CNS) manifestations, including micro-
cephaly (head circumference below the third percentile), a his-
tory of delayed development, hyperactivity, attention deficits,
(a)
(b)
(c)
(d)
Mesoderm
Ectoderm
Neural
plate
Neural
groove
Neural
fold
Neural
tube
Endoderm
Neural
crest
Somites
Neural
tube
Rostral
Caudal
Figure 31.1-2
Formation of the neural tube and neural crest. These schematic illustrations follow the early development of the nervous system in the
embryo. The drawings above are dorsal views of the embryo; those below are cross sections.
A.
The primitive embryonic central nervous
system (CNS) begins as a thin sheet of ectoderm.
B.
The first important step in the development of the nervous system is the formation of the
neural groove.
C.
The walls of the groove, called neural folds, come together and fuse, forming the neural tube.
D.
The bits of neural ecto-
derm that are pinched off when the tube rolls up are called the neural crest, from which the peripheral nervous system (PNS) will develop.
The somites are mesoderm that will give rise to much of the skeletal system and the muscles. (Reprinted from Bear MF, Conners BW,
Paradiso MA, eds.
Neuroscience: Exploring the Brain
. 2
nd
ed. Philadelphia: Lippincott Williams & Wilkins. 2001:179, with permission.)
