Shingles, or Herpes Zoster, is a painful rash caused by the reactivation of the Varicella-Zoster Virus (VZV). VZV is the same virus that causes chickenpox. After the primary infection, the virus remains dormant in nerve tissue, reactivating years or decades later as a localized rash. Its appearance during pregnancy naturally raises questions about fetal health.
Shingles and Miscarriage Risk
Shingles does not increase the risk of miscarriage or cause significant complications for the developing fetus. This low risk is due to the mother’s pre-existing immunity to the virus. Since Shingles is a reactivation, the mother’s immune system already contains antibodies from the initial chickenpox infection. These antibodies keep the viral replication localized to the affected nerve and skin area.
The viral load in the bloodstream during a Shingles outbreak is very low, making it unlikely for the virus to cross the placenta. Studies investigating Shingles in pregnancy have not found evidence of an increased rate of miscarriage or birth defects. The infection is usually confined to one side of the body, and the primary concern is managing the mother’s pain and discomfort.
Shingles Versus Primary VZV Infection
The risk profile to the fetus depends entirely on whether the mother has Shingles or a primary VZV infection (chickenpox). Shingles is a secondary infection, contained by the mother’s established immunity. This maternal immune response minimizes the risk of the virus reaching the fetus.
In contrast, a primary VZV infection means the mother has no pre-existing immunity, resulting in a systemic infection. The virus circulates widely throughout the mother’s bloodstream before an effective immune response can be mounted. This widespread circulation dramatically increases the chances of the virus crossing the placenta. Therefore, a first-time chickenpox infection poses a much greater concern for the pregnancy than Shingles.
Fetal Outcomes of VZV Exposure
The most severe fetal risks are associated with a primary VZV infection (chickenpox), not Shingles. Outcomes depend heavily on the timing of the infection. If the primary infection occurs during the first 20 weeks of gestation, there is a small risk (0.4% to 2%) of the fetus developing Congenital Varicella Syndrome (CVS). CVS involves birth defects resulting from the virus crossing the placenta and damaging fetal tissue.
Specific manifestations of CVS include skin scarring, underdeveloped limbs, eye abnormalities, and neurological issues such as microcephaly. The risk of CVS becomes negligible after 20 weeks of gestation, as the fetal immune system is more developed. However, a primary infection later in pregnancy, especially close to delivery, poses a different risk to the newborn.
If the mother develops chickenpox between five days before and two days after delivery, the infant is at risk of developing severe neonatal varicella. During this critical window, the mother has not had enough time to transfer protective antibodies across the placenta, but the virus has already infected the fetus. This can result in a severe, life-threatening infection in the newborn. If the maternal rash appears more than five days before delivery, antibodies have likely been transferred, offering the baby some protection.
Management and Protective Steps
Pregnant individuals who develop any painful or blistering rash should contact a healthcare provider immediately for diagnosis. If Shingles is confirmed, antiviral medications such as acyclovir or valacyclovir can be prescribed to reduce the severity and duration of the outbreak. These medications are considered safe for use during pregnancy and are most effective when started within 72 hours of rash onset.
Protective measures primarily focus on preventing a primary VZV infection in non-immune pregnant individuals, as this poses the greater risk. If a pregnant person is exposed to VZV, a blood test can confirm immunity. In cases of significant exposure, a non-immune pregnant person may be given Varicella-Zoster Immune Globulin (VZIG) for passive protection.
Individuals planning a pregnancy who are unsure of their immunity should discuss VZV vaccination with their doctor, as the live-attenuated varicella vaccine cannot be given during pregnancy. The Shingles vaccine is also not recommended during pregnancy but can be considered before or after the gestational period.