The herpes simplex virus (HSV) is a common infective agent during both childhood and adult life. Although HSV-1 is traditionally considered to be responsible for orolabial herpes and HSV-2 for genital herpes, there is considerable overlap. HSV is important in pregnancy because of the adverse effects of primary infection on maternal health and premature labour, and also because of the risks of primary neonatal infection, which may be severe.
Problems and special considerations
Primary infection may result in local lesions and viraemia with systemic effects, for example malaise, myalgia, meningitis, encephalitis and hepatitis. Local lesions may reappear weeks to years later, often following emotional or physical stress. Primary infection is associated with a ~40% incidence of neonatal transmission. Secondary infection is not associated with viraemia and the risk of neonatal transmission is under 3%.
Women with severe primary infection may present in premature labour or with acute systemic manifestations, whereas those with active genital lesions may present for caesarean section, performed to reduce neonatal transmission.
It is not known whether epidural or spinal anaesthesia increases the likelihood of central nervous system involvement if there is a history of secondary HSV infection, although there are published series of obstetric regional anaesthesia performed without problems. Epidural morphine is associated with up to 11 times the risk of recurrence of oral lesions compared with parenteral morphine; the mechanism is unclear but may be related to direct activation of the dormant virus in cranial nerve nuclei. Fentanyl has been implicated in a single report. However, there are other confounding factors such as emotional and physical stress that may also account for recurrence.
In primary infection, avoidance of regional anaesthesia is often advised, but less is known about the risks since primary infection at the time of delivery is rare. There are series of successful regional blocks in the presence of primary infection, but numbers are very small.
Management options
Treatment of HSV in pregnancy is by aciclovir, which may be given orally, or intravenously in cases of severe disseminated infection. Caesarean section is the recommended method of delivery when the risk of vertical transmission to the fetus is high, such as in women who have acquired their first infection in the third trimester, or in those with primary active lesions in the last 6 weeks of pregnancy or at the time of delivery. The benefit of caesarean section in the latter group, however, may be reduced if the membranes have been ruptured for longer than 4 hours. Women who present in labour with a recurrent infection, or those who have acquired the primary infection in the first two trimesters of pregnancy and whose labour does not start in the following 6 weeks, may be offered a vaginal delivery.
Mothers should be fully informed of the theoretical risks and benefits of regional anaesthesia, especially before caesarean section when the alternative (i.e. general anaesthesia) is generally perceived as being more hazardous. The neonate born of a mother with HSV should be carefully evaluated for evidence of infection.
Key points
• Primary herpes simplex virus (HSV) infection may cause severe systemic illness and premature labour.
• Neonatal infection may occur if there are active genital lesions.
• The risk of central neural infection following regional anaesthesia in secondary HSV infection is thought to be theoretical only.
• Epidural morphine may cause recurrence of orolabial HSV lesions.
Further reading
Chen YH, Rau RH, Keller JJ, Lin HC. Possible effects of anaesthetic management on the 1 yr followed-up risk of herpes zoster after caesarean deliveries. Br J Anaesth 2012; 108: 278-82.
Corey L, Wald A. Maternal and neonatal herpes simplex virus infections. N Engl J Med 2009; 361: 1376-85.
Foley E, Clarke E, Beckett VA, et al.; Royal College of Obstetricians and Gynaecologists.
Management of Genital Herpes in Pregnancy. London: RCOG, 2014. https://www.rcog.org.uk/gl obalassets/documents/guidelines/management-genital-herpes.pdf (accessed December 2018).
Lee R, Nair M. Diagnosis and treatment of herpes simplex 1 virus infection in pregnancy. Obstet Med 2017; 10: 58-60.