Fetal Varicella Syndrome and Perinatal Varicella Risk
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Direct answer
Varicella in pregnancy is chickenpox that can cause serious maternal pneumonia, most often in the third trimester. Fetal varicella syndrome is uncommon and most likely after maternal infection between 13 and 20 weeks, while maternal rash from five days before to two days after delivery threatens the newborn. Varicella zoster immunoglobulin is given after significant exposure in non-immune women, and aciclovir is used for maternal pneumonia or serious disease.
What you must remember
- Maternal pneumonia: The most serious maternal complication, presenting several days after the rash with cough, breathlessness and hypoxia; smokers and third-trimester women are at higher risk.
- Fetal varicella syndrome: Affects fewer than 2 percent of infants, highest when maternal infection occurs between 13 and 20 weeks.
- Features of fetal varicella: Limb hypoplasia, dermatomal scarring, cortical atrophy, chorioretinitis and Horner syndrome.
- Neonatal varicella: Maternal rash from five days before to two days after delivery; the newborn can develop severe, sometimes fatal, disease.
- VZIG: Varicella zoster immunoglobulin for non-immune pregnant women with significant exposure, ideally within 10 days of contact, and for exposed newborns.
- Aciclovir: Oral aciclovir for uncomplicated maternal disease when started within 24 hours of rash onset; intravenous aciclovir for pneumonia.
- Vaccine: Live varicella vaccine is contraindicated in pregnancy, and pregnancy should be avoided for one month after vaccination.
A pathway for exposure and active disease
A pregnant woman with a varicella exposure or rash is managed by immunity, gestational age and timing relative to delivery. The steps below follow the usual sequence.
- Establish immunity: Ask about past chickenpox or vaccination and check VZV IgG where history is unclear; immune women need no prophylaxis.
- Give VZIG early: Varicella zoster immunoglobulin is given to non-immune women after significant exposure, ideally within 10 days of contact.
- Treat active maternal disease: Oral aciclovir is started within 24 hours of rash onset for uncomplicated disease, and intravenous aciclovir is given for pneumonia.
- Watch for pneumonia: Review breathlessness, cough and oxygen saturation, because pneumonia often appears several days after the rash, and chest imaging is done if needed.
- Plan around delivery: A maternal rash from five days before to two days after delivery calls for VZIG to the newborn and neonatal review.
- Scan the fetus: Detailed ultrasound after maternal infection between 13 and 20 weeks looks for growth restriction, limb shortening and structural defects; risk falls after 20 weeks.
Where the examiner tries to catch you
Varicella questions combine the maternal pneumonia risk with the neonatal window and the post-exposure drugs.
- Trap: Giving live varicella vaccine to a non-immune pregnant woman after exposure Correct: Live vaccine is contraindicated in pregnancy, and VZIG is the immediate post-exposure option.
- Trap: Calling congenital varicella inevitable after maternal chickenpox at any time Correct: Fetal varicella syndrome is uncommon and concentrated between 13 and 20 weeks.
- Trap: Assuming the newborn is at risk after chickenpox months before delivery Correct: Maternal antibodies protect the newborn; the danger window is five days before to two days after delivery.
Frequently asked questions
What is the risk window for neonatal varicella?
Neonatal varicella is at risk when the mother develops rash from five days before to two days after delivery. In this window the newborn lacks protective maternal antibodies and may develop severe, sometimes fatal, disease.
When is VZIG given to a pregnant woman exposed to varicella?
VZIG is given to a non-immune pregnant woman after significant exposure, ideally within 10 days of contact. Oral aciclovir may be considered where VZIG is unavailable, although its role in this setting is less well established.
What is fetal varicella syndrome?
Fetal varicella syndrome is a congenital pattern with limb hypoplasia, dermatomal scarring, cortical atrophy and eye defects such as Horner syndrome. It occurs in fewer than 2 percent of infants, mostly after maternal infection between 13 and 20 weeks.
Which drug treats varicella pneumonia in pregnancy?
Intravenous aciclovir treats varicella pneumonia in pregnancy, started promptly with oxygen support as needed. Oral aciclovir is used for uncomplicated maternal disease when it is started within 24 hours of rash onset.