Congenital Infections of the Newborn
Definition
Congenital infections in the newborn are either transmitted via the placenta
during pregnancy or acquired from the birth canal at the time of labour.
TORCH is an acronym based on the first letters of some of the more important
infections affecting babies and children. The letters stand for: (TO) Toxoplasmosis,
(R) Rubella, (C) Cytomegalovirus, (H) Herpes simplex.
These infections were grouped together as a convenient reminder of their common features. The term TORCH is now outdated and best avoided, but some still find it a useful aid in remembering some causes of infection. It is now known that many other agents may cause congenital infections, such as:
● Varicella zoster (the chickenpox virus).
● Syphilis.
● Hepatitis B.
● Parvovirus.
● HIV (human immune deficiency virus).
● Chlamydia trachomatis.
● Mycoplasma.
● Group B streptococcus.
It is therefore more useful to consider these infections separately and
look at the unique features of each infection.
● The time to provide information to mothers about
these infections is before pregnancy begins, because this is the best time
for preventive measures.
● The first trimester is usually the most dangerous
time for the mother to catch these infections, because there is greater
risk of the foetus being affected.
● Infection in the mother can often be accompanied
by very trivial symptoms or even none at all, so the condition is not usually
diagnosed.
● Infection in the mother does not always mean the
baby will be affected. For many infections, the baby is more at risk at
particular stages of pregnancy (eg. first trimester for rubella, at delivery
for herpes simplex). For some the infection risk at any stage is low.
● Some infections can be avoided by the mother through
simple measures, such as immunisation for rubella during childhood and before
pregnancy. Some infections are treatable, eg. Syphilis is treated effectively
with penicillin.
The effects of congenitally acquired infection may be quite different from
and more severe than, the effects of the same infection acquired in the
usual way (eg, rubella in children usually results in a mild fever and itchy
rash while congenital rubella can result in a baby being born with deafness,
cataracts, heart defects or other problems).
Toxoplasmosis
Throughout the world there are wide regional variations in the prevalence
of Toxoplasma infections. In Australia, between 60 and 70% of women of child-bearing
age are susceptible, but Toxoplasma infection during pregnancy is uncommon,
occurring in approximately two in every 1,000 pregnancies.
Toxoplasmosis is mainly acquired from cat faeces or eating undercooked meat.
The infection may be asymptomatic or produce only mild symptoms in the mother.
Infection early in the pregnancy may cause the death of the foetus and abortion;
infection later can cause foetal damage, stillbirth or a live born infant
with damage to the brain and body organs. Infection in the mother does not
always cause congenital disease in the baby. Overall, the rate of transmission
is about 50% and is dependent upon the stage of the pregnancy during which
the maternal infection developed. The risk of foetal infection is 15%, 45%
and 70% during the first, second and third trimesters respectively. In contrast
the risk of foetal damage resulting in spontaneous abortion or symptomatic
disease at birth is greatest if infection occurs early in pregnancy.
While severe disease is seen in 80% of infants delivered to mothers who
acquired the infection in the first trimester, only 50% of infants are symptomatic
at birth if the maternal infection was acquired in the second trimester.
Although maternal infection in the third trimester rarely results in foetal
damage, neurological injury and chorioretinitis may appear months or years
later. Symptomatic babies are born with hydrocephalus, chorioretinitis and
cerebral calcification. There is treatment available for infected babies,
but in contrast to those with subclinical infection the outlook for babies
with neurological involvement is uncertain and must be guarded.
Rubella
In general, the earlier in pregnancy the mother contracts rubella, the greater
the risk of severe generalised involvement of the foetus (cataracts, deafness,
congenital heart disease, microcephaly, hepatosplenomegaly and thrombocytopenia).
In the first trimester, the rate of foetal infection is nearly 50% of which
as many as 80% develop the Congenital Rubella syndrome. Proven rubella infection
with a blood test before 13 weeks gestation can be a reason for termination
of the pregnancy. Between 13 and 16 weeks, the foetal infection rate is
10 to 30% resulting in one-third becoming deaf and demonstrating mild intellectual
disability. After 16 weeks the risk is very low. Immunisation decreases
the incidence of infection in the general population and therefore reduces
the risk to pregnant mothers and their babies.
Rubella immunisation is offered to all children in Australia, resulting
in a low rate of congenital rubella. However, the best method of personal
prevention is for women to have their rubella immunity checked before trying
to conceive and to be immunised if necessary.
Cytomegalovirus
Cytomegalovirus (CMV) is the most common cause of intra- uterine infection.
About 50% of women of childbearing age remain susceptible to CMV infection
and 1% of women who are susceptible at the beginning of pregnancy will acquire
a primary infection during pregnancy. Unlike rubella, foetal damage may
follow primary infection, or rarely recurrent infection, at any stage of
pregnancy. Risk of foetal infection is greatest (30–40%) during primary
maternal infection. Nevertheless, only 10% of infants born with congenital
CMV are symptomatic at birth. These more severely affected infants are more
likely to have been exposed to a primary maternal infection during the first
trimester. Most (80 - 90%) infants who are symptomatic at birth (hepatosplenomegaly,
jaundice, petechiae and microcephaly) and another 10% of infants with asymptomatic
infection at birth develop late complications such as sensori-neural deafness,
intellectual disability or seizures.
Herpes simplex
Herpes simplex (HSV) infection of the newborn is usually acquired from the
mother at birth, through genital herpes of which the mother is frequently
unaware. It occurs in approximately one in 10,000 births. As with CMV, the
risk of perinatal herpes is greater with a primary (40%) than recurrent
(less than 5%) infection. It can cause local infection of the skin, eyes
and mucous membranes and may disseminate to involve multiple organs including
the lungs, liver, adrenals and brain. Even with the availability of anti-viral
agents such as Acyclovir, mortality and morbidity within survivors remains
high in neonates with meningoencephalitis or disseminated forms of the disease.
If it is known that the mother has active herpes during labour, prolonged
rupture of membranes and foetal scalp electrode monitoring should be avoided.
The baby may be delivered by elective caesarean section because of the risks
of infection with a vaginal delivery. However, caesarean section does not
always prevent perinatal infection.
Varicella zoster (Chickenpox)
This is uncommon in women of child bearing age, and the risk to babies is
usually low. The risk of a baby being affected by congenital infection and
abnormalities is 1-2% if the mother is infected during second trimester,
sometimes resulting in severe damage with skin scarring, ocular lesions,
seizures and limb abnormalities. Transmission later in pregnancy can result
in the baby being affected by zoster (shingles-like rash) or chickenpox
(the usual infection). If the mother develops chickenpox between five days
before delivery to two days after, the baby is given zoster immune globulin
because protective maternal antibodies will not be present by the time of
delivery. The development of varicella lesions in the infant five to 10
days after delivery is associated with severe disease and requires parenteral
Acyclovir therapy.
Syphilis
Active maternal syphilis is uncommon in Australia and occurs in about one
in every 2,000 pregnancies, but in untreated primary or secondary disease
there is a high risk of stillbirth, premature delivery, neonatal death,
or developing features of congenital syphilis. While foetal infection can
be cured by treatment of the mother, preferably early in pregnancy, if foetal
damage has occurred it may not be reversible. A major problem is that the
clinical and laboratory signs of early infection in the neonate are not
always present at birth, but may develop in the first few weeks or months
of life in the untreated infant. By contrast, penicillin treatment of the
affected infant in the neonatal period prevents the complications of late
congenital syphilis.
Hepatitis B
In Australia, up to 2% of pregnant women are chronic hepatitis B surface
antigen (HBsAg) carriers. Thirty percent are HBeAg positive and these mothers
can infect nearly 90% of their offspring. Infection occurs predominantly
during delivery from abrasions in the infant's skin or mucosa, or from small
materno-foetal bleeds across the placenta during labour. Almost all infections
in the neonate are asymptomatic, but more than 90% become chronic carriers
themselves and are at high risk of chronic liver disease, including cirrhosis
and liver cancer, by middle age. Screening of all pregnancies for HBsAg
and in the future, universal immunisation against hepatitis B will eventually
reduce the burden of the disease to the affected individuals and the community.
Parvovirus
This virus quite commonly causes a mild febrile illness with rash in older
children and adolescents (eg slapped cheek and fifth disease). It is easily
mistaken for rubella and like this illness can also cause joint symptoms
in adults. Approximately 50% of adults are susceptible and transmission
rates in households reach 50%, while within schools or day care centres
rates of 20–30% are observed. Foetal infection occurs in 30% of maternal
infections with 10% foetal death occurring predominantly in the second trimester
from severe anaemia and hydrops foetalis.
HIV (Human immune deficiency virus)
Infection is transmitted transplacentally, during delivery or from breast
milk. The transmission rate is between 10 and 30%. It is believed that the
virus is transmitted predominantly at delivery. However, in nearly 15% of
perinatal HIV infections, breast feeding has been implicated. Infected neonates
can be asymptomatic for several years but up to 30% will develop symptoms
and become very ill within the first few months of life.
Chlamydia trachomatis
This sexually transmitted infection is often asymptomatic in the mother,
although infected women may have inflammation of the cervix, fallopian tubes
or urethra. The infection is transmitted during delivery. Estimates of Chlamydia
prevalence in pregnant Australian women are 1-2 %. Conjunctivitis will develop
in 50-60% of infants born to infected mothers, but is rarely severe. A more
serious complication is Chlamydia pneumonia, which may develop in as many
as 30% of exposed infants and can result in a prolonged respiratory illness
with cough and tachypnoea. For both infections oral erythromycin is the
treatment of choice.
Mycoplasmas
Genital mycoplasmas have been suggested as cause for recurrent miscarriage,
chorioamnionitis, preterm birth, and low birth weight, stillbirth and post-partum
fever. It is uncertain whether there is any value in screening for these
organisms, as other factors may have caused these adverse outcomes.
Group B streptococcus
Group B streptococcus (GBS) is the commonest cause of overwhelming sepsis
(respiratory distress, shock and/or meningitis) in neonates during the first
week of life and may occur at any time up to eight to ten weeks. Approximately
15% of pregnant women carry GBS in their vagina and the principal risk factor
for disease (two in every 1000 live births) is absence of type-specific
maternal IgG antibody. Preterm labour, prolonged rupture of the membranes
and maternal fever are associated with a higher risk of infection. Infected
neonates are treated with antibiotics. Until an effective vaccine is developed,
some experts recommend intra-partum antibiotics for pregnancies at high
risk for GBS infections.
Clinical Presentation
In general, intra-uterine infections are suspected in two clinical situations:
During pregnancy
A mother-to-be who is non-rubella immune (or does not know her status) is
tested (perhaps because of a flu-like illness or contact with a suspected
case of rubella) and is found to have been infected. Since rubella is the
only TORCH infection screened for at booking, the other infections are usually
only suspected during pregnancy if abnormalities in the foetus are detected
on ultrasound scan or if a pregnant woman has contracted a flu-like illness
(unexplained fever, rash, joint pain, etc.). Sera and suitable specimens
are collected as soon as possible and in all cases, discussion of testing
and counselling on various aspects of management must be undertaken. Treating
the mother during pregnancy (eg. if a recognisable illness is found and
diagnosed) and then the baby during the first 12 months of life may prevent
or reverse damage for many of these children. The option of termination
of pregnancy, if indicated, should be discussed with the mother by expert
medical staff able to present a balanced overview of likely procedures and
outcomes.
After pregnancy
The baby may have signs which lead parents and clinicians to suspect an
abnormality and clinicians may test for one or more congenital infections.
These signs may include combinations of an abnormal appearance, eye abnormalities,
seizures, small size, big or small head, cardiac murmur, enlarged abdominal
organs, jaundice, skin rashes, petechiae and others. Testing is likely to
be more effective if aimed at identifying the type of infection most likely
to be present (based on clinical findings). With most modern laboratories
the waiting time for results should not exceed more than a few days.
Testing
The collection of appropriate specimens as soon as possible and testing
maternal/infant serum in parallel is of utmost importance. Maternal sera
collected early in pregnancy should be stored for at least 12 months. Close
cooperation with the microbiology laboratory and experts in congenital infections
is important when congenital infection is suspected.
● Toxoplasma: Specific IgM antibody in blood (if
IgG positive), tissue culture, PCR (polymerase chain reaction testing) and
follow-up serology may be required.
● Rubella: Specific IgM antibody in blood (if IgG
positive) and viral culture.
● CMV: Isolation of the virus in the throat washings
or urine in the first two to three weeks of life. Absence of IgG in blood
is a quick method of excluding the diagnosis.
● HSV: HSV can be difficult to diagnose but the
virus can be identified by PCR, direct antigen testing by immunofluorescence
or by electron microscopy. The virus should be cultured if perinatal infection
is suspected. Direct communication between the clinician and the microbiologist allows optimal use of laboratory resources and the most logical sequence of testing.
Advice For Women Contemplating Pregnancy
Women can reduce the risk of these infections during pregnancy by following
these recommendations:
● Young children should be fully immunised (including
MMR).
● Mothers should know their rubella immune status,
preferably before trying to conceive but certainly during pregnancy by presenting
for 'booking' investigations.
While pregnant:
● Wash hands after changing nappies or handling
any body secretions.
● Wash hands before and after food preparation.
● Avoid undercooked meats.
● Do not handle cat faeces while pregnant.
● Try not to kiss children full on the mouth.
● Do not garden without gloves.
● Do not share cutlery or toothbrushes with children.
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