Herpes simplex treatment in pregnancy, during labour

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Herpes Simplex in Pregnancy and Labour

Background

Genital HSV in pregnancy is clinically significant because of the risk of neonatal transmission — which carries high mortality and morbidity. The key determinants of risk are:

Nature of infection at delivery: first episode vs. recurrent
Presence of active genital lesions at the time of labour
Gestational timing of primary acquisition

Neonatal herpes occurs in ~1:3,000–20,000 live births; 85% of cases are acquired at delivery, 10–15% postnatally from non-maternal sources, and only 5% in utero.

Risk of Neonatal Transmission

Scenario	Transmission Risk
Recurrent genital HSV, vaginal delivery with active lesions	2–5%
Primary/first-episode genital HSV at delivery, vaginal	26–56%
Caesarean section (culture-positive cervix)	~1%

The 70% of mothers of neonates with HSV are asymptomatic at delivery with no prior history — so history-taking alone cannot reliably identify risk.

— Andrews' Diseases of the Skin, p. 429; Harrison's Principles of Internal Medicine 22E

Treatment in Pregnancy

First Episode / Primary Infection During Pregnancy

Antiviral treatment is recommended for all initial episodes of genital HSV in pregnancy (except possibly in the first month, where there may be an increased risk of spontaneous abortion).

Acyclovir 400 mg orally three times daily for 10 days (standard dose)
This is especially important for initial episodes in the third trimester
IV acyclovir should be considered for severe/disseminated primary infection

Acyclovir is safe in pregnancy: "No adverse effects to the fetus or newborn have been attributable to acyclovir. Acyclovir can be used in all stages of pregnancy and among women who are breastfeeding." — Harrison's, p. 1547

Suppressive Therapy in Late Pregnancy

For women with recurrent genital herpes or a first-episode during pregnancy, suppressive therapy from 36 weeks gestation until delivery is recommended to:

Reduce clinical recurrences at term
Reduce the frequency of caesarean delivery for active HSV
Reduce viral shedding at delivery

Regimens:

Acyclovir 400 mg orally three times daily from ~34–36 weeks until delivery
Valacyclovir 500 mg orally twice daily from ~34 weeks until delivery

Note: Suppressive therapy reduces the risk of needing caesarean section but may not fully prevent neonatal transmission.

— Harrison's, p. 1547; Andrews' Diseases of the Skin, p. 429; Fitzpatrick's Dermatology

Management During Labour

Caesarean Section Indications

Caesarean section is recommended when a woman presents in labour with:

Active genital lesions (cervical, vaginal, or vulvar)
Prodromal symptoms (tingling, burning in genital area)

This reduces transmission risk from ~8% to ~1% in culture-positive women. However, it does not prevent all neonatal herpes cases.

Caesarean section may not reliably prevent neonatal HSV when membranes have been ruptured for ≥24 hours. — Fitzpatrick's Dermatology

Intrapartum Precautions

Avoid scalp electrodes in any delivery where cervical HSV shedding is possible — associated with up to sevenfold increased risk of neonatal infection
Avoid vacuum-assisted delivery — increases relative risk of neonatal transmission 2–27 times
Routine prenatal cultures are not recommended in recurrent herpes (they don't predict shedding at delivery); they may be of value in women with primary genital HSV during pregnancy

Preventing Maternal Acquisition During Pregnancy (Serodiscordant Couples)

If the woman is HSV-seronegative and her partner is HSV-positive:

Barrier contraception (condoms) for all sexual contact
Avoid orogenital contact if partner is HSV-1 positive and woman is HSV-1 negative
Valacyclovir suppression of the infected partner can be considered
Abstinence in the third trimester further reduces risk

These measures are important because acquisition of primary HSV near term carries the highest risk of neonatal disease.

Neonatal Treatment (if infected)

Disease type	Treatment
SEM (skin, eyes, mouth)	IV acyclovir × 14 days
CNS disease	IV acyclovir × 21 days
Disseminated disease	IV acyclovir × 21 days

Prognosis: localized SEM disease is rarely fatal with treatment; CNS/disseminated disease has 15–50% mortality even with treatment, and >50% of survivors have neurologic disability.

— Andrews' Diseases of the Skin, p. 429

Summary Table

Clinical Situation	Management
Primary HSV in pregnancy	Acyclovir 400 mg TDS × 10 days; IV acyclovir if severe
Recurrent HSV, antepartum	Suppression from 36 wks: acyclovir 400 mg TDS or valacyclovir 500 mg BD
Active lesions/prodrome at labour onset	Caesarean section
No active lesions, recurrent HSV	Vaginal delivery can be considered
Intrapartum	Avoid scalp electrodes; avoid vacuum delivery
Neonatal HSV (SEM)	IV acyclovir 14 days
Neonatal HSV (CNS/disseminated)	IV acyclovir 21 days

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