Consequences of varicella and herpes zoster in pregnancy: prospective study of 1739 cases

Review of varicella zoster seroepidemiology in India and Southeast Asia

Varicella zoster virus (VZV) predominantly affects children in temperate countries, with near-universal seroconversion occurring by late childhood. However, in tropical regions, VZV infection is common in adolescents and adults. This review identifies age-related VZV seroprevalence patterns in a number of Asian countries which indicate that seroconversion in tropical countries occurs at a later age than in temperate countries. Seasonal and regional variations in acute disease within some Asian countries suggest that temperate climates might favour transmission of the varicella virus, with incidence peaking during cooler months and in cooler, more temperate regions. VZV infection is often more severe in adults than in children, suggesting that tropical countries may be at risk of greater morbidity and mortality as a result of later-age seroconversion. Susceptibility of pregnant women and their infants, and of people infected with HIV/AIDS is also cause for concern. Vaccination may be beneficial in reducing the impact of VZV in Asian populations.

Varicella in pregnancy

Varicella-zoster virus may cause serious infection, particularly pneumonia, in adult women. Women of child-bearing age should be questioned about immunity to varicella preconceptually, and offered serological testing, and VARIVAX vaccine if indicated. All pregnant patients should be questioned about immunity to varicella during their first prenatal appointment. Susceptible patients should be counseled to avoid contact with individuals who have chickenpox. If exposure occurs, VZIG should be administered within 96 hours in an attempt to prevent maternal infection. Varicella embryopathy may occur as a result of maternal infection particularly in the first half of pregnancy with an incidence of 1% to 2%. Varicella of the newborn is a life-threatening illness that may occur when a newborn is delivered within 5 days of the onset of maternal illness or after postdelivery exposure to varicella. Susceptible neonates should receive VZIG. Acyclovir is active against the varicella-zoster virus, and treatment is indicated in seriously ill adults and neonates.

Varicella-zoster virus infection in Australia

OBJECTIVE

To determine the epidemiology of varicella-zoster virus (VZV) infection in Australia using currently available data sources.

DESIGN

Analysis of national death data (23 years), congenital and neonatal cases (one year) and attendances at sentinel general practices (two years); hospital admissions in NSW and SA (six years); serological studies in 1995 involving antenatal clinics in Sydney and Brisbane and child-care centre staff and refugees in Sydney; and case-ascertainment in 1995 in South Western Sydney among public hospital staff, child-care centre staff and the community.

RESULTS

In Australia, there have been an average of 3.5 deaths from chickenpox (mostly children) and 11 from herpes zoster (mostly older people) each year since 1980. The crude death rate for chickenpox has declined (p > 0.05). In 1995, there were 14 cases of neonatal and two of congenital varicella. Average annual admission rates for NSW and SA showed 1,200 hospital bed-days used for chickenpox, more than 20% with complications, and more than 7,300 bed days for zoster; annually more than 880 in-patient admissions were complicated by VZV. Most people encounter the virus in their first 15 years, but some remain susceptible into their 20s; 25% of cases and 37% of hospital admissions for chickenpox occur in people > or = 15 years of age.

CONCLUSION

VZV infection involves people of all ages. It causes substantial morbidity and mortality, particularly at the extremes of life. The death rate from chickenpox but not zoster has fallen since the introduction of acyclovir in the 1980s. Surveillance of VZV infection must be given priority once vaccines become available, to monitor changes in morbidity and mortality.

Immediate and long term outcome of human parvovirus B19 infection in pregnancy

OBJECTIVE

To estimate more precisely the risk of fetal loss and congenital abnormalities after maternal parvovirus B19 infection, and to assess the long term outcome for surviving infants.

DESIGN

Prospective cohort study of pregnant women with confirmed B19 infection with follow up of the surviving infants. The rate of fetal loss in the study cohort was compared with that in pregnant women with varicella.

SETTING

Cases reported by laboratories in England and Wales between 1985-1988 and 1992-1995.

SAMPLE

Four hundred and twenty-seven pregnant women with B19 infection and 367 surviving infants of whom 129 were followed up at 7-10 years of age.

METHODS

Questionnaires to obstetricians and general practitioners on outcome of pregnancy and health of surviving infants. Maternal infection confirmed by B19-specific IgM assay and/or IgG seroconversion.

RESULTS

The excess rate of fetal loss in women with B19 infection was confined to the first 20 weeks of gestation and averaged 9%. Seven cases of fetal hydrops followed maternal infections between 9 and 20 weeks of gestation (observed risk 2.9%, 95% CI 1.2-5.9). No abnormalities attributable to B19 infection were found at birth in surviving infants (observed risk 0%, upper 95% CI 0.86%). No late effects were found at 7-10 years.

CONCLUSIONS

Around 1 in 10 women infected before 20 weeks of gestation will suffer a fetal loss due to B19. The risk of an adverse outcome of pregnancy after this stage is remote. Infected women can be reassured that the maximum possible risk of a congenital abnormality due to B19 is under 1% and that long term development will be normal.

[Zona in children]

Herpes zoster is the clinical consequence of a late reactivation of the varicella zoster virus (VZV). It infects mainly the elderly, but pediatric cases are not uncommon. It occurs mostly in immunocompromised children, or in infancy after reactivation of latent VZV infection acquired transplacentally during intrauterine life. Rarely, herpes zoster occurs in otherwise normal children, especially following varicella during the first year of life. Clinical presentation of herpes zoster in children is identical to that of adult, with usually a benign course. The impairment of cellular and non specific immunity (Natural Killer cells) appears to have a particular role in the occurrence of herpes zoster. Treatment of the usual form comprises antiseptic measures and prevention of pruritus. In immunocompromised children, the infection is generally severe and disseminated, and can result in high rates of morbidity and mortality, thus requiring specific intravenous antiviral therapy with antiviral drugs such as acyclovir without delay. There is no single approach towards VZV infection prevention in immunocompromised hosts. Vaccination with live attenuated varicella vaccine, has proved to be efficient and safe in immunocompromised children.

Antiviral prophylaxis and treatment in chickenpox. A review prepared for the UK Advisory Group on Chickenpox on behalf of the British Society for the Study of Infection

Prophylactic intervention with varicella-zoster immunoglobulin early in the incubation period can prevent or attenuate the disease manifestations of varicella in susceptible contacts at high risk from this infection. Detailed guidelines are issued in the UK Department of Health publication on Immunization against Infectious Disease. Sensitive immunoassays are available for investigation of antibody status and subclinical seroconversion. Live attenuated varicella vaccine, which has been used successfully post-exposure as well as electively elsewhere, is at present not generally available in the UK. Effective protocols for prophylaxis against varicella with the antiviral agent aciclovir are not yet established. The nucleoside analogue aciclovir (syn: acyclovir, Zovirax) is effective in inhibiting replication of VZV when given at a dosage higher than that required for treatment of HSV, and is currently the only available and approved treatment for varicella in the U.K. Intravenous aciclovir therapy for 5-10 days is effective for varicella in neonates and the immunocompromised, and for varicella pneumonia or other complications in adults and children, if begun early. Oral aciclovir is only effective if begun with 24 h of onset of rash. With that proviso. it is recommended for treatment of varicella in otherwise healthy adults and adolescents, but not for routine use in children under 13 years of age unless they are sibling contacts or have other medical conditions. Aciclovir has a high therapeutic index and good safety profile, but caution is advised with use in pregnancy.

First trimester pregnancy loss associated with varicella zoster virus infection: histological definition of a case

Pathological demonstration of varicella infection in first trimester aborted tissue is reported. A 24-year-old primigravida manifested chickenpox infection about 38 days after her last menstrual period or at 24 days age of the embryo. The conceptus survived another 4 to 5 weeks. The macerated embryo and placental tissue revealed nuclear changes consistent with varicella infection. Immunohistochemical stains and electron microscopy were confirmatory.

[Chickenpox in pregnancy]

Chickenpox is rare during pregnancy (1 to 7 per 10,000). The infection can be severe for the mother and indirectly may affect the fetus. Before 20 weeks of amenorrhea, the varicella-zoster virus may be responsible for a rare embryofetopathy (incidence rate: 0.4 to 2%). After the 20th week of amenorrhea, fetal infection is not symptomatic, but it may lead to neonatal or infantile herpes zoster infection. During the perinatal period, a primary maternal infection may be responsible for severe neonatal varicella if delivery occurs prior to maternal antibody production. Practical guidelines are proposed according to the date of infection during pregnancy and prenatal diagnosis using amniocentesis and/or cordocentesis is discussed.

Review of 26 years' hospital admissions for chickenpox in North London

The epidemiology of chickenpox admissions to an Infectious Diseases Unit was studied over 26 years. Risk factors, markers of disease severity, and complications were analysed in patients admitted during the last 5 years. Some 613 patients were admitted with chickenpox over three 5-year periods between 1968 and 1993. There was a 2.23-fold increase in the number of adults admitted from home between the first and last period. Patients of European origin showed a three-fold increase. The mean age of adults rose from 26.2 to 34.3 years. Some 23% of adults had varicella pneumonitis. Smokers were six times more susceptible to pneumonitis than were non-smokers. Adult asthmatics were not at increased risk, whereas 42% of asthmatic children had chest complications. Seventeen of the 18 immunocompromised patients had a relatively uncomplicated course. Of the children, 32% had secondary skin infections, with no excess complications among those with eczema. Thrombocytopenia and elevated aspartate transaminases were four times and twice, more frequent in adults than children, respectively. These features occurred mostly in males. The male-to-female admission ratio was 2:1 in adults, and 1.2:1 in children. Males in both age groups showed a trend to more severe disease and more primary complications than did females. Our data showed an increase in adult chickenpox admissions. We have identified asthma as a risk factor for pulmonary complications in children, but not adults, and male gender as an independent risk factor for severe chickenpox.

Prenatal diagnosis of fetal varicella-zoster virus infection with polymerase chain reaction of amniotic fluid in 107 cases

OBJECTIVE

Varicella, resulting from primary infection by varicella zoster virus, carries a risk of severe congenital varicella. Prenatal diagnosis is rarely applied because methods remain to be validated.

STUDY DESIGN

From 1989 to 1994, 107 women contracted clinical varicella before 24 weeks of pregnancy. Amniocentesis was performed in all cases, with simultaneous fetal blood sampling in 82 cases. Virus was detected in amniotic fluid by cell culture inoculation and polymerase chain reaction. Fetal blood was tested for anti-varicella zoster virus immunoglobulin M.

RESULTS

Of the 107 amniotic fluid samples tested, nine of 107 (8.4%) were positive by polymerase chain reaction, but only two of these (1.8%) were positive in cell culture; none of the blood samples from infected fetuses were positive for specific anti-varicella zoster virus immunoglobulin M. The outcome of 99 pregnancies was fully documented.

CONCLUSION

The risk of transplacental passage before 24 weeks of pregnancy was 8.4% in our series. The risk of congenital varicella is 3 in 107 (2.8%) and that of isolated postnatal varicella zoster infection is 3 in 78 (3.8%). Polymerase chain reaction is more sensitive than cell culture for the detection of varicella zoster virus in amniotic fluid.

Transmission of varicella-vaccine virus from a healthy 12-month-old child to his pregnant mother

A 12-month-old healthy boy had approximately 30 vesicular skin lesions 24 days after receiving varicella vaccine. Sixteen days later his pregnant mother had 100 lesions. Varicella-vaccine virus was identified by polymerase chain reaction in the vesicular lesions of the mother. After an elective abortion, no virus was detected in the fetal tissue. This case documents transmission of varicella-vaccine virus from a healthy 12-month-old infant to his pregnant mother.

Detection of herpes simplex DNA in semen and menstrual blood of individuals attending an infertility clinic

OBJECTIVE

To determine a possible link between herpes simplex virus 1 (HSV) and infertility.

METHOD

A specifically designed polymerase chain reaction with nested primers, was developed and used to test for HSV in 153 men and 20 women attending an infertility clinic.

RESULTS

HSV DNA was detected in 37 (24%) out of 153 semen samples and in 11 (55%) out of 20 menstrual blood samples. However, HSV DNA (0%) was not detected in the semen of 16 males with children. A significant association between the evidence for infertility and an HSV positive test was observed in men (Fisher's exact test, p = 0.024), and a stronger effect was found in females after failed in vitro fertilization (Fisher's exact test p = 0.0086).

CONCLUSION

This is the first report of the detection of herpes simplex virus DNA in semen and menstrual blood. Encouraging preliminary results justify antiviral therapy in case of a positive test.

Prenatal sonographic diagnosis of congenital varicella infection--a case report

We report a case of fetal varicella infection following the diagnosis of maternal varicella infection at 13 weeks of pregnancy. Anomalies noted sonographically at 26 weeks' gestation included oligohydramnios, symmetrically impaired fetal growth, limb anomalies, a thin placenta, and widespread dystrophic calcification of the abdominal cavity and chest, including the lungs and myocardium. Some of these sonographic anomalies have been reported previously. However, to our knowledge, prenatal diagnosis of calcification of the lungs and myocardium has not been described.

Prevention and Control of Varicella-Zoster Infections in Healthcare Facilities

Varicella-zoster virus (VZV) is the causative agent of two diseases: varicella (chickenpox) and zoster (shingles). Although varicella generally is a mild disease in children, serious morbidity and mortality are common if infection occurs in neonates, pregnant women, adults, or immunocompromised patients. For this reason, the Centers for Disease Control and Prevention recommends that all the hospitals institute control measures. Healthcare workers should be screened for VZV immunity and, if susceptible, should receive the recently licensed Oka/Merck vaccine (unless contraindicated). This article reviews nosocomial outbreaks associated with VZV and provides detailed algorithms for preexposure immunization and postexposure management of healthcare workers exposed to VZV.

Use of a reformulated Oka strain varicella vaccine (SmithKline Beecham Biologicals/Oka) in healthy children

The first live-attenuated Oka strain varicella vaccines needed to be stored at -20 degrees C. Reformulation of this vaccine by SmithKline Beecham Biologicals has provided a vaccine shelf life of up to 2 years when stored at +4 degrees C to +8 degrees C. In this study the immunogenicity and reactogenicity of two different production lots of this reformulated vaccine at two different titres each, which corresponded to the release and expected expiry titres, were evaluated. A double-blind randomised clinical trial was conducted in healthy children aged from 9 to 24 months. Immunogenicity was assessed by the measurement of varicella specific antibodies in paired serum samples taken before and from 35 to 63 days post vaccination. Reactogenicity was assessed by the evaluation of any untoward reactions occurring up to 42 days post vaccination. In order to assess protective efficacy, parents of these subjects were contacted approximately 6 months after completion of the trial. One hundred and ninety-one subjects were recruited into the study. Of the 181 initially seronegative subjects who completed the trial according to the protocol, 179 showed seroconversion (98.9%). Reactions to the vaccine were minor and observed in 46/191 (24%) of subjects. Rashes were present in 19, fever in 22, and both fever and rash in 5. Rashes were mainly maculo-papular in nature but were vesicular in 6. Febrile reactions were shortlived. After a 6-month follow up period, attenuated varicella with minor clinical symptoms was diagnosed in 6/52 vaccinees who had close contact with natural varicella (attack rate = 11.5%).

CONCLUSION

This reformulated vaccine was well tolerated, highly immunogenic and provided protection against varicella. In increased stability allowing refrigerator storage makes it a good candidate for mass vaccination programmes.

Varicella-zoster virus

Varicella-zoster virus (VZV) is a ubiquitous human alphaherpesvirus that causes varicella (chicken pox) and herpes zoster (shingles). Varicella is a common childhood illness, characterized by fever, viremia, and scattered vesicular lesions of the skin. As is characteristic of the alphaherpesviruses, VZV establishes latency in cells of the dorsal root ganglia. Herpes zoster, caused by VZV reactivation, is a localized, painful, vesicular rash involving one or adjacent dermatomes. The incidence of herpes zoster increases with age or immunosuppression. The VZV virion consists of a nucleocapsid surrounding a core that contains the linear, double-stranded DNA genome; a protein tegument separates the capsid from the lipid envelope, which incorporates the major viral glycoproteins. VZV is found in a worldwide geographic distribution but is more prevalent in temperate climates. Primary VZV infection elicits immunoglobulin G (IgG), IgM, and IgA antibodies, which bind to many classes of viral proteins. Virus-specific cellular immunity is critical for controlling viral replication in healthy and immunocompromised patients with primary or recurrent VZV infections. Rapid laboratory confirmation of the diagnosis of varicella or herpes zoster, which can be accomplished by detecting viral proteins or DNA, is important to determine the need for antiviral therapy. Acyclovir is licensed for treatment of varicella and herpes zoster, and acyclovir, valacyclovir, and famciclovir are approved for herpes zoster. Passive antibody prophylaxis with varicella-zoster immune globulin is indicated for susceptible high-risk patients exposed to varicella. A live attenuated varicella vaccine (Oka/Merck strain) is now recommended for routine childhood immunization.

Varicella and pregnancy

OBJECTIVE

To appreciate the risk of embryo-foetopathy in case of maternal varicella occurring before 20 weeks of gestation, as well as the maternal complication risk (notably pulmonary) in case of maternal varicella occurring the third trimester of pregnancy.

METHOD

Over the period from January 1987 to February 1995, 20 patients were managed for maternal varicella confirmed during the pregnancy. From these observations, the authors, by studying the literature, attempt to better specify the real fetal and/or maternal complication risk in case of maternal varicella.

RESULTS

In their personal series of 20 cases, including 17 before 20 weeks of gestation, the authors have noted no embryo-foetopathy. Similarly, no maternal complication (notably pulmonary complication), has been found. Careful study of the literature allows to specify some points. In case of varicella before 20 weeks, one observes an identical frequency of spontaneous abortions, as compared to the general population and a moderated increase of the frequency of premature delivery. The risk of congenital varicella syndrome reaches about 1.3%. Finally the risk of neonatal varicella consists in a maternal infection which occurs during the perinatal period and which is source of a high perinatal morbidity. The prenatal diagnosis is based essentially and currently, on the amniocentesis with viral research by polymerase chain reaction (PCR) in the amniotic fluid, completed by a ultrasound supervision.

CONCLUSION

The occurrence of maternal varicella during the pregnancy is rare (0.7/1000) because more than 90% of women are immunized. The risk of congenital varicella syndrome is limited to the 20 first weeks and seems very weak, authorizing therapists to reassure patients presenting a varicella during their pregnancy. Nevertheless, the risk of pulmonary complications for the mother, in case of varicella during the third trimester, does exist and requires appropriated treatment.

Acyclovir for the prevention and treatment of varicella zoster in children, adolescents and pregnancy

Varicella causes a mild, self-limiting childhood disease that may reactivate years later as shingles. In immunocompromised patients with altered cell mediated immunity, and rarely in healthy individuals, varicella results in a life-threatening infection. The antiviral drug, acyclovir, substantially reduces the mortality and risk of severe disease in these groups of patients. Early commencement of acyclovir is recommended for children with both varicella and altered cell mediated immunity, newborns during the first 2 weeks of life, preterm infants in the neonatal nursery, and severe varicella or shingles (including ocular zoster) in any patient, as well as during pregnancy. Acyclovir may be considered in children with serious cardiopulmonary disease or chronic skin disorders where varicella may exacerbate the underlying disease or increase the risk of secondary bacterial sepsis. Acyclovir, however, is not recommended for healthy individuals without severe disease, as a prophylactic agent against varicella, for asthmatics receiving aerosolized or low-dose oral steroids and/or as treatment of the post-varicella syndromes. When acyclovir is prescribed it should be given intravenously to those with severe disease, those at risk of dissemination and in children younger than 2 years of age.

Chickenpox in mid-trimester pregnancy: always innocent?

A case of congenital varicella infection is presented, in which despite profound cerebral damage, the cardinal features of cicatricial skin lesions and limb shortening were absent. The case is compared with previously described cases, and with published series, in which this combination is uncommon. The risks of maternal varicella infection to the developing fetus are discussed in the light of recent prospective studies which demonstrate a rather lower risk than had previously been thought to be the case.

Prévention de la varicelle chez le personnel d'encadrement des enfants

Varicella is an ubiquitous, highly contagious viral disease of childhood which may be severe in non immune adults and pregnant women. Pediatric staff is particularly at risk of nosocomial varicella and susceptible staff should be prospectively idenfitifed by serologic tests. A number of different approaches may be used to prevent disease depending on the at risk population and the preexposure or postexposure status. This article reviews and evaluates the different approaches to the prevention of varicella in pediatric staff.

Preconception counseling for the primary care physician

All health care providers that interact with women of childbearing age should understand the potential benefits of preconception counseling and to approach the evaluation in a thorough manner during routine health maintenance visits. With the increased number of patients enrolled in managed care programs, health maintenance visits provide the unique opportunity to educate women contemplating pregnancy regarding the potential influences of their lifestyle and health status on the future pregnancy. It is becoming increasingly apparent that interventions made during the preconception period are just as crucial as the subsequent 9 months of prenatal care to achieve an optimal maternal-fetal outcome. Some guidelines for the preconception evaluation have been provided, and the implications of chronic medical illness on pregnancy have been discussed.

Maternal varicella during pregnancy: correlation of maternal history and fetal outcome with placental histopathology

The authors examined the records from 73 women diagnosed with varicella during pregnancy to correlate placental findings with maternal history and fetal outcome. Fifty-eight of the mothers delivered at the authors' institution, and 19 placentas were available for review. The onset of symptoms of varicella occurred from 27 weeks before delivery to 1 day postpartum. Only on e of the newborns delivered at the authors' institution was diagnosed with probable varicella at birth; the remainder had no unequivocal evidence of infection; however, serological studies were not performed on most of the newborns. The placenta from the newborn with probable varicella showed extensive basal chronic villitis with a lymphohistiocytic infiltrate and occasional multinucleated giant cells. Two other placentas showed rare foci of chronic villitis, and the remainder showed no villitis or other viral-associated changes. Twenty-four (33%) of the 73 women developed varicella pneumonia, and one woman died. Although varicella during pregnancy is associated with high maternal morbidity, fetal disease is uncommon. Most placentas show no virus-associated lesions; however, chronic villitis with multinucleated giant cells in association with a recent history of maternal varicella may be predictive of neonatal infection.

Severe varicella pneumonia in adults in Stockholm County 1980-1989

Varicella pneumonia in adults is considered to be a serious complication, with mortality rates of 9-50%, but the true incidence and clinical course is not known. We therefore studied all adult patients in Stockholm County hospitalized during the period 1980-1989 with varicella. 36/305 (12%) varicella patients admitted to hospital were diagnosed as having pneumonia, corresponding to a mean incidence of 0.32/100,000 inhabitants per year. In most patients the pneumonia had a mild to moderate clinical course and no deaths occurred (mortality rate 0%, CI95 [0, 9.7]). However, 13 patients had a severe tachypnoea (> or = 30 breaths/min) and 4 of these required intensive-care treatment. Ten patients were treated with acyclovir, in most cases combined with corticosteroids. We conclude that the incidence of severe varicella pneumonia is low in the adult population, and that the mortality rate of this complication is probably lower than previously described.

Prenatal diagnosis of congenital varicella infection

Fourteen fetuses at risk of Varicella-Zoster virus (VZV) infection underwent prenatal diagnosis at 10-24 weeks' gestation by a combination of chorionic villus sampling, amniocentesis, and fetal blood sampling. Polymerase chain reaction (PCR) was done on fetal and placental tissues, using primers which define a 221 bp region of the gene coding for the 44 kD protein of VZV. Positive cases were further analysed by dot blot hybridization, using radiolabelled DNA probes corresponding to the Hind III fragment VZV genome. The rate of placental/fetal infection was 36 per cent (5/14 fetuses: 2/11 in the first and 3/3 in the second trimester). At post-mortem examination, two aborted fetuses had hydrocephaly and VZV DNA was found in most of the examined tissues. The nine women who tested negative at prenatal investigation delivered healthy neonates whose VZV-specific IgM antibody titres were negative and none of them developed herpes zoster infection. In view of the high frequency of fetal VZV infection and the reported low rate of malformations, the role of invasive prenatal diagnosis in women who acquire the infection in the first half of gestation is mainly that of reassurance when the test is negative.

The risks and benefits of antimicrobial therapy in pregnancy

Antimicrobial agents, especially antibiotics, are prescribed in pregnancy for various specific indications related to pregnancy per se (e.g. chorioamnionitis), for infections otherwise unrelated to but complicating pregnancy (e.g. pneumonia, bacterial endocarditis) and prophylactically for conditions which if untreated would have an adverse outcome for the pregnancy (e.g. asymptomatic bacteriuria). The selection of an agent will depend on the likely pathogen, stage of pregnancy, special pharmacokinetic factors related to the stage of pregnancy, safety of the drug and cost. Some classes of antibiotics can be taken throughout the 3 trimesters (e.g. beta-lactams), while others are completely contraindicated (e.g. tetracyclines) and others are to be avoided in certain trimesters (e.g. sulphas are contraindicated in the third trimester). The choice of an appropriate antimicrobial agent must be weighed against the potential adverse outcome of a particular infection, the drug safety and spectrum of activity.