31.3 Intellectual Disability
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forms of maternal infection that go undetected. Maternal rubella
can be prevented by immunization.
Cytomegalic Inclusion Disease.
In many cases, cyto-
megalic inclusion disease remains dormant in the mother. Some
children are stillborn, and others have jaundice, microcephaly,
hepatosplenomegaly, and radiographic findings of intracere-
bral calcification. Children with intellectual disability from the
disease frequently have cerebral calcification, microcephaly,
or hydrocephalus. The diagnosis is confirmed by positive find-
ings of the virus in throat and urine cultures and the recovery of
inclusion-bearing cells in the urine.
Syphilis.
Syphilis in pregnant women was once the main
cause of various neuropathological changes in their offspring,
including intellectual disability. Today, the incidence of syphi-
litic complications of pregnancy fluctuates with the incidence of
syphilis in the general population. Some recent alarming statis-
tics from several major cities in the United States indicate that
there is still no room for complacency.
Toxoplasmosis.
Toxoplasmosis can be transmitted by the
mother to the fetus. It causes mild or severe intellectual disabil-
ity and, in severe cases, hydrocephalus, seizures, microcephaly,
and chorioretinitis.
Herpes Simplex.
The herpes simplex virus can be trans-
mitted transplacentally, although the most common mode of
infection is during birth. Microcephaly, intellectual disability,
intracranial calcification, and ocular abnormalities may result.
Human Immunodeficiency Virus (HIV).
Cognitive
impairments are well known to be associated with transmis-
sion of HIV from mothers to their babies. HIV may have both
direct and indirect influences on the developing brain. A sub-
set of infants born infected with HIV may develop progressive
encephalopathy, intellectual disabilities, and seizures within
the first year of life. Fortunately, over the last two decades,
there has been a dramatic decrease in perinatal HIV trans-
mission due to a combination of antiviral agents provided to
mothers during pregnancy and delivery, obstetric interventions
that reduce risk, and administration of zidovudine (ZDV) as a
prophylaxis for six weeks to newborns exposed to HIV. In the
United States, the highest rate of reported pediatric acquired
immunodeficiency disease (AIDS) occurred in 1992, with
1,700 cases reported compared to less than 50 cases reported
annually now. In the United States, fewer than 300 cases of
HIV transmission from mother to child were reported in 2005.
However, vertical transmission of HIV from mother to child
around the world, especially in Africa, is considerable. Most
babies born to HIV-infected mothers in the United States are
not infected with the virus.
Fetal Alcohol Syndrome.
Fetal alcohol syndrome (FAS)
results from prenatal alcohol exposure and can lead to a wide
range of problems in the newborn. According to the Centers
for Disease Control and Prevention, FAS in the United States
occurs at a rate ranging from 0.2 to 1.5 per 1,000 live births.
FAS is one of the leading preventable causes of intellectual
disability and physical disabilities. The typical phenotypic
picture of a child with FAS includes facial dysmorphism com-
prising hypertelorism, microcephaly, short palpebral fissures,
inner epicanthal folds, and a short, turned-up nose. Often, the
affected children have learning disorders and ADHD, and in
some cases intellectual disability. Cardiac defects are also
frequent. The entire syndrome occurs in up to 15 percent of
babies born to women who regularly ingest large amounts of
alcohol. Babies born to women who consume alcohol regu-
larly during pregnancy have a high incidence of ADHD, learn-
ing disorders, and intellectual disability without the facial
dysmorphism.
Prenatal Drug Exposure.
Prenatal exposure to opioids,
such as heroin, often results in infants who are small for their
gestational age, with a head circumference below the tenth per-
centile and withdrawal symptoms that appear within the first
2 days of life. The withdrawal symptoms of infants include
irritability, hypertonia, tremor, vomiting, a high-pitched cry,
and an abnormal sleep pattern. Seizures are unusual, but the
withdrawal syndrome can be life-threatening to infants if it
is untreated. Diazepam (Valium), phenobarbital (Luminal),
chlorpromazine (Thorazine), and paregoric have been used to
treat neonatal opioid withdrawal. The long-term sequelae of
prenatal opioid exposure are not fully known; the children’s
developmental milestones and intellectual functions may
be within the normal range, but they have an increased risk
for impulsivity and behavioral problems. Infants prenatally
exposed to cocaine are at high risk for low birth weight and
premature delivery. In the early neonatal period, they may have
transient neurological and behavioral abnormalities, including
abnormal results on EEG studies, tachycardia, poor feeding
patterns, irritability, and excessive drowsiness. Rather than a
withdrawal reaction, the physiological and behavioral abnor-
malities are a response to the cocaine, which may be excreted
for up to a week postnatally.
Complications of Pregnancy.
Toxemia of pregnancy and
uncontrolled maternal diabetes present hazards to the fetus and
can potentially result in intellectual disability. Maternal malnu-
trition during pregnancy often results in prematurity and other
obstetrical complications. Vaginal hemorrhage, placenta previa,
premature separation of the placenta, and prolapse of the cord
can damage the fetal brain by causing anoxia. The use of lithium
during pregnancy was recently implicated in some congenital
malformations, especially of the cardiovascular system (e.g.,
Ebstein’s anomaly).
Perinatal Period.
Some evidence indicates that prema-
ture infants and infants with low birth weight are at high risk
for neurological and subtle intellectual impairments that may
not be apparent until their school years. Infants who sustain
intracranial hemorrhages or show evidence of cerebral isch-
emia are especially vulnerable to cognitive abnormalities. The
degree of neurodevelopmental impairment generally correlates
with the severity of the intracranial hemorrhage. Recent stud-
ies have documented that, among children with very low birth
weight (less than 1,000 g), 20 percent had significant disabili-
ties, including cerebral palsy, intellectual disability, autism, and
low intelligence with severe learning problems. Very premature
children and those who had intrauterine growth retardation were
