Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made. (Formerly, these situations were captured under a "C Recommendation".) This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade. For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.
Contents
Herpes simplex infection in the newborn is thought to be acquired from the mother during passage through an infected birth canal. Experts agree that the infant’s exposure to the virus can be prevented by cesarean section if the maternal infection is recognized at the onset of labour and within 4 to 6 hours after rupture of the membranes. However, maternal infection is asymptomatic in 70% of cases. The difficulty in detecting asymptomatic infection has led to the practice of screening women considered to be at high risk (those with a history of recurrent genital infection or active disease during the current pregnancy and those whose sexual partners have proven genital herpes).
However, identification and screening of pregnant women at risk of recurrent infection has not been shown to prevent neonatal death or illness from infection and is not recommended. There is currently no screening strategy for asymptomatic women with no known history of herpes virus exposure, even though the risk of transmission to the newborn is higher in primary infections.
Burden
of SufferingThe rising incidence of neonatal herpes simplex has reflected a nationwide increase in the prevalence of herpes simplex. In 1981 the incidence was 12 cases per 100,000 live births, as estimated from a hospital-based study in Washington. In other studies primary infection was responsible for 29-35% of cases. Although both the transmission rate and the attack rate are higher with primary infection, recurrent infection accounts for a greater proportion of the burden of neonatal infection.
ManeuverThe screening test consists of culture of a cervical smear for herpes simplex virus. However, since the results are not available for 3 days, the decision to deliver vaginally or by cesarean section is usually based on the penultimate culture result, which has a very low predictive validity for the presence of infection at the time of delivery. Arvin and associates<1> followed 414 women with a history of recurrent genital herpes. None of 17 women with positive antepartum culture results had positive results at delivery, and 5 of 354 asymptomatic mothers with negative antepartum results had positive results at delivery (sensitivity 0%).
Effectiveness
of Prevention and TreatmentNot only is the risk of transmission higher in primary infection, but the outcome is more likely to be severe. Prober and collaborators<4> studied the hypothesis that serologically verified primary infection would be associated with a worse neonatal outcome than that associated with recurrent infection. Through screening of 6,904 mother-infant pairs for both herpes simplex virus antibodies and herpes simplex at delivery they identified infection in 14 women and 3 infants. Two of the three infants were born of the two mothers with primary infection; meningitis developed in one of the two infants at 12 days of age.
Among women with recurrent disease the risk of transmission and clinical disease in the newborn appears to be lower. Of 34 infants inadvertently delivered vaginally from mothers with recurrent infection at the time of delivery and followed up without treatment, all remained asymptomatic. Calculation of the 95% confidence interval within which the mean risk of disease could be expected among these infants resulted in an upper estimate of risk of 8%. A genital lesion consistent with herpes simplex was present in 56% of the mothers, underscoring the importance of careful clinical examination among asymptomatic women.
Decision analysis was used to evaluate 9 strategies for prevention of neonatal HSV (involving physical exam, culture, and antigen testing of all or high-risk women). Physical examination at labour was found to be the optimal strategy given the goal of minimizing the ratio of excess cesarean sections to cases of neonatal HSV infection averted; however, about 30 excess cesarean sections would be performed for each case averted. Strategies involving high-risk women were associated with 36-178 excess cesarean sections per HSV case averted.
The use of cesarean section among symptomatic women only will lead to some missed cases; however, an economic evaluation of the strategy of sequential screening revealed that it would cost US$37 million for each case prevented. A national screening program in the U.S. would prevent 1.8 cases/year.
Recommendations
of OthersThe Infectious Diseases and Immunization Committee of the Canadian Pediatric Society recommends that all pregnant women be questioned during prenatal visits about any personal history of genital HSV infection or similar history in their sexual partner(s). Signs and symptoms of genital HSV infection should be sought in all women during pregnancy but weekly antepartum cultures for HSV are not recommended, even in women with a history of genital HSV infection. However, all women should be questioned about recent symptoms and examined carefully for clinical evidence of genital HSV infection on admission for delivery; and all newborn infants whose mothers have genital lesions or a history of infection should be examined/observed.
The U.S. Preventive Services Task Force recommends screening pregnant women with active lesions for genital herpes simplex virus;<6> this recommendation is currently being reviewed.
In December, 1992, the Infectious Disease Society of America (IDSA) recommended that serial viral cultures for women with recurrent infections be abandoned. The IDSA recommended that women with histories of genital herpes should be provided education and reassurance. Assays for detection of HSV antigen or viral cultures should not be performed except to evaluate clinically apparent lesions. While routine samples for cultures were recommended at delivery for women with histories of genital herpes, even in the absence of visible lesions, the lack of established utility for such screening was emphasized. If the patient had active genital herpes when labour occurred (not including active lesions at some distance from the genital tract, e.g. buttock), cesarean section was recommended before membrane rupture or as soon thereafter as possible and viral cultures performed.<7>
Conclusions
and RecommendationsA high degree of suspicion of herpes simplex must be maintained since neonatal herpes simplex is usually severe by the time of presentation. Empiric initiation of antiviral therapy should be considered.
Based on fair evidence from well-designed cohort studies, weekly culture for herpes simplex virus should be excluded from the routine prenatal care of women with a history of recurrent herpes simplex (D Recommendation).
A history of genital herpes and clinical evidence of infection at the time of delivery should be sought. If such evidence exists, cesarean section is recommended, particularly if it is known before or within 4 to 6 hours after rupture of the membranes.<5> However, this strategy is based upon expert opinion; there is overall poor evidence to include cesarean section in, or exclude it from, routine prepartum care of symptomatic women (C Recommendation).
Unanswered
Questions (Research Agenda) EvidenceThis review was initiated in October 1988 and recommendations were finalized by the Task Force in February, 1989. A report with a full reference list was published in December 1989.<8>
Link to Structured Abstract of this review
Link to Summary Table of this review
Link to Selected References list of this review
Reprinted in modified format by the Canadian
Task Force on Preventive Health Care
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Original Copyright
© 1994 Minister of Supply and Services Canada.
Last modified March 26, 1998.
