Chitika1

Saturday 24 December 2011

INFECTIONS IN PREGNANT WOMAN


Proven infection
If a vertically transmissible infection is confirmed or cannot be excluded in a pregnant woman, the risk to the fetus depends on the stage of pregnancy and the type of infection. For some infections, it may be appropriate to determine whether the fetus has been infected (eg, CMV infection, toxoplasmosis and, in some circumstances, varicella). This requires specialised tests, such as culture or nucleic acid testing of amniotic fluid. Expert advice and appropriate investigations are essential before interventions such as termination of pregnancy or administration of potentially toxic drugs are considered.
Rubella
Although rubella is generally preventable by vaccination, congenital rubella still occurs in Australia.11 Up to 10% of women of child-bearing age are susceptible, as they have not been vaccinated, vaccination has failed, or vaccine-induced immunity has waned. Although the Australian Measles Control Campaign raised the proportion of school children immune to rubella to over 95% in 1998, 15%–20% of young men remain susceptible and a potential source of infection for pregnant women with inadequate immunity.
If infection occurs in the first trimester of pregnancy, the risk of fetal infection and damage is high (about 90% in the first two months of pregnancy, and 50% in the third), and termination of pregnancy is usually recommended. Risk of fetal damage falls steeply after the first trimester and is negligible after 16 weeks; between 12 and 16 weeks, deafness has been reported.
If a pregnant woman has close contact with or develops rubella-like illness, her IgG and IgM titres should be measured, even if she was previously positive for rubella IgG — rarely, women with apparently adequate immunity can be reinfected (although the risk of fetal abnormality is probably less than 5%, even in the first trimester12). If contact is in the second or third trimester and rubella IgG was detected in the first trimester, further investigation is not necessary. Women who remain susceptible to rubella should receive MMR vaccine post partum, unless two previous attempts at immunisation have failed.
Cytomegalovirus infection
Cytomegalovirus is the most common cause of congenital infection and non-hereditary deafness. Currently, there is no vaccine or treatment that can be given during pregnancy (ganciclovir is used to treat serious CMV infection associated with conditions such as organ transplantation or HIV/AIDS). CMV infection is transmitted by contact with saliva, urine or genital secretions and often causes mild hepatitis, atypical lymphocytosis and non-specific symptoms during the self-limiting primary infection. The virus then becomes latent, but is reactivated periodically during episodes of mild immunosuppression caused by intercurrent infection, pregnancy or stress. Reactivation is asymptomatic, except in severely immunocompromised individuals.
Primary maternal infection occurs in about 1 per 300 pregnancies in Australia and results in fetal infection in about 40% of cases (affecting 1 per 1000 infants); fetal damage is most likely early in pregnancy. Most congenitally infected infants are apparently normal at birth, but long-term sequelae, most commonly deafness and mild intellectual impairment, occur in up to 40% (10%–15% of all infants of women with primary infection during pregnancy). Symptomatic multisystem disease, characterised by growth retardation, microcephaly, intracranial calcification, thrombocytopenia and hepatitis, is uncommon.13
Reactivation of maternal infection during pregnancy can also cause fetal or perinatal infection (about 1% of infants), but sequelae are uncommon and usually mild.14 It is usually difficult to distinguish asymptomatic primary maternal infection from reactivation or to determine precisely when infection occurred.
If primary maternal CMV infection is suspected because of close contact or a compatible illness, serological and liver function tests and a blood film will usually confirm the diagnosis (case report, Box 5). More often, primary CMV infection is suspected because of a positive CMV IgM result in routine antenatal screening. False positive CMV IgM results are common, because of cross-reactions, viral reactivation or persistent low-level IgM after past primary infection. IgG avidity testing will help distinguish recent from long-past infection.15 Ideally, women who believe they are at risk of CMV infection, such as childcare workers, should be tested for IgG before conceiving.
If recent CMV infection is likely or cannot be excluded, especially in the first trimester, amniocentesis should be considered to determine whether the fetus is infected. It should be done at about 19 weeks' gestation, or at least six weeks after the likely time of infection. CMV isolation or positive nucleic acid test results from amniotic fluid indicate fetal infection, but not necessarily morbidity, while negative results indicate that severe fetal morbidity is extremely unlikely. If fetal infection is confirmed, the stage of pregnancy at which it occurred, viral load in the amniotic fluid and evidence of fetal abnormality or growth retardation on ultrasound examination may aid in considering termination of pregnancy
Toxoplasmo
Lisiske CMV infection, toxoplasmosis is usually asymptomatic or has mild, non-specific symptoms. Primary infection during pregnancy can cause serious fetal effects. However, unlike CMV infection, toxoplasmosis during pregnancy can be treated, potentially reducing the fetal effects.
Although asymptomatic women with perceived risk (eg, contact with cats) are often tested for toxoplasma IgG, pre-pregnancy or antenatal screening is not recommended. There is no clearly defined group of women at increased risk, about 75% of women are susceptible,16 and seroconversion during pregnancy is uncommon. False positive toxoplasma IgM results are not uncommon (case report, Box 6), and low levels of IgM may persist for many months or years after primary infection. Like CMV, toxoplasma infection remains latent for life, but clinical reactivation is confined to severely immunosuppressed individuals. Infants of women who are seropositive before conception are not at risk.
Toxoplasmosis is acquired through eating raw or undercooked meat or ingesting soil contaminated with toxoplasma oocysts, which are excreted in the faeces of infected cats. Pregnant women should be specifically advised to avoid these exposures (see Pre-pregnancy testing and counselling). Direct contact with cats is rarely a source of infection (they are usually infected as kittens and excrete oocysts for a relatively short time).
Investigation of suspected acute toxoplasmosis is similar to that of suspected CMV infection. If maternal infection is confirmed or cannot be excluded, antibiotic treatment appears to reduce the risk of fetal infection and sequelae,8 although this has not been confirmed by randomised controlled trials.17 For maternal infection in the first trimester, it is particularly important to determine whether the fetus is infected,18 as likelihood of fetal infection is low (about 15%), but, if it occurs, fetal damage is likely to be severe. Later in pregnancy, infection is more likely, but fetal damage is less likely and, if it occurs, less severe.19
Varicella (chickenpox)
Fetal infection occurs in 10%–15% of cases of varicella (chickenpox) in pregnant women but is usually transient and asymptomatic. The most common clinical manifestation, if any occurs, is shingles in the first year of life. However, 2%–3% of infants of women who have chickenpox in the first half of pregnancy develop fetal varicella syndrome, with potentially severe defects, including skin scarring in a dermatomal distribution, ipsilateral limb hypoplasia, visceral, neurological and eye lesions20 (Box 7). Maternal varicella within a few days before or after delivery can result in potentially severe varicella in the infant,21 who should be given zoster immune globulin (ZIG) as soon as possible after birth.
More than 90% of women of child-bearing age in Australia are immune to varicella virus,9,16 with a history of infection providing reliable evidence of immunity. If in doubt when contact occurs, pregnant women should be tested for varicella IgG as soon as possible (including those who have been vaccinated, if seroconversion has not been confirmed). If seronegative, they should be offered ZIG, preferably within 48 hours of contact (maximum, 72 hours). ZIG may not prevent infection but reduces illness severity
The diagnosis of chickenpox is usually obvious. The disease is more likely to be severe in adults than in children and may be complicated by pneumonia, especially in smokers and in the latter half of pregnancy, and is occasionally fatal. Use of aciclovir is not recommended during pregnancy, but evidence is accumulating that it has no adverse fetal effects.22 Given during the incubation period or within 24 hours of rash onset, it can reduce risk of infection or illness duration and severity. Its use should be considered during the incubation period for women who have not received ZIG, or soon after rash onset, especially in women with risk factors for severe disease, such as chronic lung disease, smoking or impaired immunity, or in the latter half of pregnancy.9 If disease progresses, admission to hospital and intravenous aciclovir are indicated.
The recommended use of varicella vaccine in susceptible women of child-bearing age will reduce the incidence of congenital and neonatal varicella in Australia.2
Parvovirus B19 infection
Parvovirus B19 causes erythema infectiosum, or fifth disease, which occurs in epidemic waves lasting two to three years, mainly among primary-school-aged children. Infection is often asymptomatic, but, like rubella, can cause rash and arthralgia or arthritis, particularly in adults. Complications of parvovirus infection during pregnancy are excess fetal loss in the first 20 weeks (up to 10% excess) and hydrops (about 3%) if maternal infection occurs between nine and 20 weeks' gestation23 (Box 9). Hydrops is caused by severe fetal anaemia and presents about five weeks after maternal infection. About a third of cases resolve spontaneously, and outcome is significantly improved in the remainder by intrauterine transfusion.24
About 60% of Australian women of child-bearing age are susceptible to parvovirus B19,25 and the annual seroconversion rate varies from about 1%–2% during non-epidemic years to 10%–15% during epidemics.26 Household and occupational contact (eg, in a schoolteacher) lead to seroconversion in about 50% and 20%–30%, respectively, of those susceptible.7
Routine antenatal screening for parvovirus antibody is not indicated, nor is it generally recommended that susceptible pregnant women with occupational exposure to the virus stay away from work. Epidemics are protracted, infection is prevalent in the community, and infectivity precedes rash onset. If contact occurs during pregnancy, IgG tests should be done to determine susceptibility and, if seronegative, repeated two to three weeks later.
If infection is confirmed during pregnancy, the fetus should be monitored for signs of hydrops by ultrasound examination over the next six to 12 weeks, with appropriate specialist referral if it occurs. PCR examination of amniotic fluid is not recommended after proven maternal parvovirus infection, but it can be helpful during investigation of non-immune hydrops of unknown cause.
Enterovirus infection
Many different enteroviruses circulate in the community, especially during summer. They cause a variety of syndromes, mainly in children, including non-specific febrile illness; maculopapular, petechial or vesicular rash (hand, foot and mouth disease); upper respiratory tract infection; and aseptic meningitis. Infection is usually benign, but can be transmitted to the infant if it occurs late in pregnancy and, rarely, can cause life-threatening meningoencephalitis, cardiomyositis or hepatitis.27 No specific intervention is available for pregnant women, but a history of relevant symptoms may aid diagnosis of severe neonatal infection.
Other infections
Many other maternal infections can be transmitted to the fetus or infant.
Listeriosis is an uncommon foodborne illness caused by Listeria monocytogenes. Pregnant women are particularly susceptible to the disease, which can result in fetal death or chronic intrauterine and congenital or perinatal infection.4,28 Investigation of symptoms such as headache, myalgia and fever associated with relatively inconspicuous gastrointestinal symptoms in a pregnant woman should include a recent dietary history and blood culture (Box 4). It is treatable with penicillin.
Gonorrhoea and chlamydial infection can be transmitted to the infant during delivery and initially cause superficial infection (conjunctivitis) or upper respiratory tract colonisation. Gonococcal infection may become disseminated, while chlamydial infection may cause pneumonia at four to six weeks of age.
Herpes simplex virus (HSV) causes neonatal HSV sepsis syndrome and encephalitis, which are often fatal or produce long-term sequelae, but are rare in Australia.29 The risk of vertical transmission of HSV (types 1 and 2) is greatest during primary maternal infection, which is often associated with viraemia. Primary genital herpes (usually type 2) may be clinically severe, with heavy and prolonged viral excretion, and higher risk of transmission to the infant during vaginal delivery than recurrent disease. Treatment with aciclovir and, if lesions are present at term, caesarean section should be considered in primary genital HSV infection. Caesarean section is not routinely recommended in women with recurrent genital herpes, as the risk of vertical transmission is small. It should be considered only if active genital lesions that cannot be covered are present at the onset of labour.30
Conclusions
Some vertically transmissible infections can be prevented or treated if detected by routine antenatal screening. Appropriate investigation and management of other suspected infections can reduce unnecessary intervention, prevent or moderate adverse outcomes and relieve anxiety. However, antenatal screening that is not based on accepted criteria or a well-defined plan of action can cause unnecessary anxiety and potentially dangerous intervention.
Evidence-based recommendations
  • Women planning pregnancy or already pregnant should be tested routinely for chronic HBV infection5 (E1), syphilis5 (E3), susceptibility to rubella5 and asymptomatic bacteriuria31 (E1, E2) and managed according to established protocols (E1–E3).
  • HIV antibody testing should be offered to all pregnant women, and any who are seropositive should be offered antiretroviral therapy1 (E2).
  • Non-pregnant women of childbearing age should be tested for immunity to varicella and offered vaccine if non-immune9 (E2).
  • Suspected infection or contact with infections known to be vertically transmissible in early pregnancy should be investigated. Intervention should be based on laboratory-confirmed maternal and, if appropriate, fetal infection and consideration of known risks of fetal damage (E3–E4, depending on infection).15,18
  • Aciclovir treatment of varicella and herpes simplex virus during pregnancy can significantly reduce morbidity in the mother and potentially in the infant9 (E2). Aciclovir is not recommended in pregnancy, although there is no evidence of adverse fetal effects22 (E3). Its use should be considered when it is judged that benefits outweigh risks.
    SOURCE: MJU.COM

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