Cold sores are small, fluid-filled blisters on or around the lips, caused by the Herpes Simplex Virus Type 1 (HSV-1). While common, an outbreak during pregnancy raises concerns about the developing baby. Careful management and discussion with a healthcare provider are necessary. Understanding the specific risks and protective measures allows expectant parents to manage the condition with confidence.
Understanding the Risks of HSV During Pregnancy and Delivery
The risk of the virus passing to the baby depends on whether the outbreak is a primary infection or a recurrence. A primary infection, contracted for the first time during pregnancy, poses the greatest concern. If this occurs near delivery, the risk of vertical transmission is high (50% to 60%) because the mother has not yet produced protective antibodies to pass to the fetus.
A recurrent cold sore outbreak carries a significantly lower risk of transmission, typically less than 3%. If the parent had cold sores previously, their body has already developed protective antibodies that cross the placenta. Most infants born to parents with recurrent oral herpes are delivered without complication.
The most serious complication is Neonatal Herpes Simplex Virus (NHSV) infection, which is rare but potentially life-threatening for a newborn. Acquisition usually occurs during the peripartum period, when the baby is exposed to the virus in the birth canal. NHSV can affect the baby’s skin, eyes, mouth, or the central nervous system. The greatest risk for NHSV occurs when a primary infection happens late in the third trimester.
Safe Treatment Options for Cold Sores During Pregnancy
Managing an outbreak involves using antiviral medications with an established safety profile for the developing fetus. Oral antiviral drugs, such as acyclovir and valacyclovir, are considered safe for use during pregnancy when the benefit outweighs the risk. Acyclovir is often the first choice due to extensive data supporting its safety in pregnant individuals.
These systemic medications interfere with the virus’s ability to replicate, reducing the severity and duration of the outbreak. Topical treatments are also an option for managing a localized cold sore. Acyclovir cream is safe because it is not absorbed into the bloodstream at levels high enough to affect the fetus.
For those with frequent recurrent outbreaks, doctors may recommend suppressive therapy later in pregnancy. This involves taking an oral antiviral daily, typically starting around 36 weeks of gestation. This treatment reduces the likelihood of having an active lesion or viral shedding at the time of delivery.
Preventing Transmission to the Infant
Preventing transmission addresses both the time of delivery and the immediate postpartum period. If an expectant parent has an active genital lesion or prodromal symptoms (like tingling or pain) at the onset of labor, a Cesarean section may be recommended. This prevents the baby from contacting the virus in the birth canal.
An active labial cold sore (on the mouth or lip) generally does not require a Cesarean delivery. For a vaginal birth, doctors recommend covering any non-genital lesion with an occlusive dressing to minimize contact risk. It is important to communicate all symptoms and outbreaks to the healthcare team.
After the baby is born, strict hygiene prevents postnatal transmission of the virus. If the parent has an active cold sore, they must practice rigorous handwashing before touching the infant or their items. Avoiding kissing the baby is the most important action, as the virus can pass directly to the newborn. Covering the lesion or wearing a mask until the cold sore is fully healed provides protection against accidental contact.