Genital Herpes Simplex Virus type 2 (HSV-2) is a widespread infection that requires careful management during pregnancy. The virus itself does not typically affect the pregnancy’s course or the developing fetus. The primary concern is transmission to the newborn, which most often happens around the time of birth. Medical oversight focuses on mitigating this risk to ensure a healthy outcome.
Risk of Transmission to the Fetus and Newborn
Transmission of HSV-2 to the infant can occur during gestation, birth, or after delivery. The highest risk path is peripartum transmission, where the newborn contacts the virus in the mother’s genital tract during vaginal delivery. Exposure occurs if the mother is actively shedding the virus, meaning the virus is present on the skin or mucosal surfaces, often due to a visible outbreak or asymptomatic shedding.
The risk of transmission depends on whether the mother has a primary or recurrent infection at delivery. A mother who acquires a primary HSV infection late in the third trimester faces the highest risk, with transmission rates estimated between 30% and 50%. This elevated risk exists because the mother’s immune system has not had sufficient time to produce protective antibodies (IgG) that can cross the placenta to shield the baby.
Conversely, a mother with a history of recurrent HSV-2 infection carries a significantly lower risk of transmission, typically less than 1% to 5%. With a long-standing infection, maternal antibodies are passed to the fetus, providing protection even if a recurrent outbreak occurs. Transmission to the fetus while still in the uterus (in utero transmission) is rare but can occur with a primary infection, potentially leading to severe outcomes such as microcephaly or skin lesions.
When transmission occurs, the resulting condition is neonatal herpes, a severe and potentially life-threatening infection. Neonatal herpes can affect the skin, eyes, and mouth, or disseminate to major organs or the central nervous system, causing brain damage or developmental delays. Early diagnosis and treatment are imperative for the best possible outcome.
Antiviral Management During Pregnancy
Antiviral therapy is a standard strategy used throughout pregnancy to manage HSV-2 and decrease transmission risk. Medications like acyclovir and valacyclovir are commonly used. Data from pregnancy registries indicate they are safe for use during gestation, with no increased risk of major birth defects. These medications reduce the frequency and severity of outbreaks and minimize the period of viral shedding.
For mothers with a history of recurrent genital herpes, suppressive therapy is typically initiated at or beyond 36 weeks of gestation. The goal of this prophylactic treatment is to suppress the virus, significantly lowering the chance of an active outbreak at labor and delivery. A common regimen involves taking a daily dose of acyclovir or valacyclovir until birth.
Clinical trials demonstrate that suppressive therapy reduces the need for Cesarean delivery due to active herpes recurrence. For mothers who experience a primary HSV infection during the third trimester, the healthcare provider may recommend continuing antiviral medication from diagnosis until delivery. This continuous treatment manages the primary infection, which is associated with a longer duration of viral shedding.
Delivery Strategy and Preventing Neonatal Infection
The delivery strategy assesses the mother’s condition at the onset of labor to prevent the baby from contacting the virus. If a mother with recurrent HSV-2 has no active genital lesions or prodromal symptoms (such as tingling or burning), a vaginal delivery is safe. Cesarean delivery is not recommended in this scenario, as the low transmission risk does not justify the risks of major surgery.
A Cesarean section is recommended if the mother presents with active genital lesions or prodromal symptoms at the beginning of labor or when membranes rupture. This surgical delivery bypasses the infected birth canal, significantly reducing the risk of exposure. If a mother has a primary infection in the third trimester, a Cesarean section may also be offered, even without visible lesions, due to prolonged, high-concentration viral shedding.
If the membranes have ruptured, delivery proceeds immediately when active lesions are present. When lesions are absent, the decision to wait for a vaginal birth balances the risk of infection against the risks of prematurity if rupture occurred before term. Invasive procedures during labor, such as internal fetal monitoring or the use of forceps, are generally avoided with active lesions to prevent trauma that could increase the risk of infection.
Post-Delivery Care and Long-Term Considerations
After delivery, the focus shifts to monitoring the newborn and preventing postnatal transmission. Newborns exposed to HSV-2 (e.g., those delivered vaginally when the mother had active lesions) may be closely monitored and sometimes receive post-exposure prophylactic antiviral medication. Monitoring is important because neonatal herpes symptoms can appear in the first few weeks of life.
Breastfeeding is generally safe and encouraged for mothers with HSV-2, as the virus is not typically transmitted through breast milk. The mother must ensure there are no active herpes lesions on the breast or nipple. If a lesion is present, feeding from that specific breast must be temporarily avoided until the lesion has healed, and the expressed milk from that side should be discarded.
Good hand hygiene is the most effective way to prevent postnatal transmission from lesions elsewhere on the mother’s body. Mothers with an active outbreak should cover the lesions and wash their hands thoroughly before touching the baby. Antiviral medications used to manage maternal HSV-2, such as acyclovir and valacyclovir, are safe during breastfeeding because only a minimal amount transfers into the milk.