Chickenpox in the third trimester can affect both the pregnant person and baby, but the risks depend on when the infection starts. The main concerns are complications in the parent, including pneumonia, and infection in the newborn if chickenpox occurs close to delivery. Contact your maternity team urgently after a possible exposure or if a rash appears; early assessment can guide testing, treatment, and plans for the baby.
Why is chickenpox a concern during the third trimester?
Chickenpox, also called varicella, is a highly contagious infection caused by the varicella-zoster virus. Although it is often a mild illness in children, a first infection during pregnancy can cause more serious illness in the pregnant person and may affect the baby.
During the third trimester, the main concerns are complications affecting the pregnant person's health and the possibility of the newborn developing chickenpox around the time of birth. The timing of the infection matters because the baby receives protective antibodies from the parent during pregnancy, and there may not be enough time for this protection to develop if infection occurs shortly before delivery.
The Centers for Disease Control and Prevention (CDC) identifies pneumonia as a major complication of chickenpox during pregnancy. Some studies have suggested that pneumonia may occur more often or be more serious when infection develops in the third trimester, although other studies have not consistently confirmed this difference.
Developing chickenpox during pregnancy does not automatically mean that the baby will be harmed. Prompt medical assessment helps the care team evaluate the circumstances, arrange treatment when appropriate, and prepare for any care the newborn may need.
How can chickenpox affect the baby in late pregnancy?
The risks to the baby depend partly on how close the infection occurs to the expected delivery date. Infection earlier in pregnancy raises different concerns from infection near birth. In the third trimester, the timing of maternal symptoms in relation to delivery is particularly important.
Chickenpox between 28 and 36 weeks
According to the Royal College of Obstetricians and Gynaecologists (RCOG), chickenpox acquired between 28 and 36 weeks may remain in the baby's body without causing symptoms at birth. The virus may become active again later in childhood, potentially causing shingles. This is different from the rare congenital varicella syndrome associated primarily with infection earlier in pregnancy.
If chickenpox develops during this period, the maternity team will consider the stage of pregnancy, the parent's condition, and the expected delivery date when planning follow-up. The infection does not mean that a baby will necessarily develop symptoms or long-term complications.
Chickenpox after 36 weeks
When chickenpox occurs during the final weeks of pregnancy, there is a greater concern that the baby may develop chickenpox around birth. RCOG estimates that about one in four babies may develop the infection when the pregnant person catches chickenpox during the four weeks before delivery. This is an estimate for that period, not a prediction of what will happen in an individual pregnancy.
The most concerning timing is when the maternal rash starts shortly before delivery or around the time the baby is born. The CDC's clinical guidance for people at risk for severe varicella identifies maternal chickenpox beginning five days before delivery through two days after delivery as a period when the newborn is at risk of neonatal varicella.
Newborn chickenpox can be serious. A baby may be particularly vulnerable when born before the parent's immune system has had enough time to produce and transfer protective antibodies. If the infection develops near delivery, the maternity and newborn teams can coordinate monitoring and preventive treatment when indicated.
What symptoms can occur with chickenpox during pregnancy?
Chickenpox often begins with general symptoms before the characteristic rash becomes noticeable. The timing and pattern can differ between individuals, and these symptoms alone cannot confirm the cause of an illness.
- Fever: A raised temperature may occur before the rash or while new spots develop.
- Feeling unwell: Fatigue, headache, reduced appetite, and general discomfort may occur.
- Itchy rash: Small spots can develop into fluid-filled blisters and later form scabs.
- New spots appearing over time: Different stages of the rash may be visible at the same time.
The CDC's guidance on chickenpox symptoms and complications describes the typical rash as itchy, with fluid-filled blisters that eventually crust over. The rash may begin on the face, chest, or back before spreading to other parts of the body.
Chickenpox symptoms commonly begin around 10 to 21 days after exposure. A person may be contagious before the rash appears and remains contagious until the lesions have crusted over. This means that someone who feels unwell but has not yet developed a rash may still be in the early stages of infection.
What should you do after exposure to chickenpox?
If you are in the third trimester and have been in close contact with someone who has chickenpox, contact your obstetrician, midwife, or maternity assessment service promptly. Do not wait for symptoms to appear. Tell the team when the contact occurred, how close it was, and whether you have previously had chickenpox or received the vaccine.
If you are uncertain whether you are immune, your healthcare professional may arrange a blood test to check for antibodies against the varicella-zoster virus. A history of previous chickenpox often indicates immunity, but if your history is unclear, testing can help guide decisions about preventive care.
If the exposure is significant and you are not immune, preventive treatment may be considered. Depending on local guidance and your circumstances, this may include antiviral medicine or varicella-zoster immune globulin, which provides temporary antibodies. The choice depends on factors such as immunity, the nature and timing of exposure, and the availability of treatment.
The RCOG's clinical guideline on chickenpox in pregnancy includes recommendations for managing exposure in pregnant people who are not immune, including post-exposure preventive treatment. Because the timing of these interventions matters, prompt contact with your maternity team is important even if you currently feel well.
How is chickenpox treated in the third trimester?
Treatment depends on when the rash begins, how unwell the pregnant person is, and whether complications develop. Antiviral medicines may be recommended during pregnancy, and the benefits of early treatment must be considered alongside the person's individual circumstances.
Antiviral medicine
Aciclovir, also spelled acyclovir, is an antiviral medicine used to treat chickenpox. RCOG advises that pregnant people who develop chickenpox should be offered a course of oral aciclovir when they are assessed within 24 hours of the rash appearing. It may help reduce fever and symptoms, and early assessment allows treatment to be considered at the appropriate time.
The CDC's clinical guidance notes that oral aciclovir or valacyclovir may be recommended for pregnant people with chickenpox, particularly in the second and third trimesters. More serious illness, including chickenpox complicated by pneumonia, may require hospital admission and intravenous aciclovir. Treatment decisions should be made by the healthcare team rather than through self-medication.
When is hospital assessment necessary?
Chickenpox can occasionally cause complications involving the lungs, liver, or nervous system. Seek emergency medical assessment if you develop breathing difficulties, marked drowsiness, a severe headache with vomiting, vaginal bleeding, a bleeding rash, or a rapidly worsening illness.
People with existing lung disease, conditions affecting their immune system, or certain treatments that suppress immunity may need additional assessment. Inform the maternity team about these conditions and any medicines you take. If you suspect chickenpox, call the healthcare facility before arriving so that staff can arrange appropriate infection-control precautions.
Can chickenpox affect the timing or planning of delivery?
A chickenpox infection during late pregnancy does not automatically mean that delivery must happen early or that a cesarean birth is necessary. Decisions about the timing and method of delivery depend on the pregnant person's condition, the stage of pregnancy, the baby's wellbeing, and how close the infection is to birth.
If the maternal rash develops shortly before the expected delivery date, the obstetric team may coordinate care with newborn specialists. They will consider the risk of neonatal infection and whether preventive treatment or close observation is needed after birth. The plan may need to be adjusted if the pregnant person becomes seriously unwell or another obstetric concern develops.
If labour begins while chickenpox is active, contact the maternity unit immediately and explain the infection or suspected exposure. Do not delay urgent maternity care, but let the team know before arrival so that they can protect other patients and staff from exposure.
How can chickenpox exposure be prevented during pregnancy?
If you know that you are not immune to chickenpox, avoid contact with people who have chickenpox or shingles during pregnancy. Tell your healthcare professional promptly about a possible exposure, because preventive options may be time-sensitive.
People with chickenpox should avoid contact with pregnant people who may not be immune and with newborn babies while they are contagious. The contagious period generally begins one to two days before the rash and continues until all lesions have crusted over.
The chickenpox vaccine is not recommended during pregnancy because it is a live vaccine. The CDC's pregnancy vaccination guidance states that varicella vaccination is contraindicated during pregnancy. If testing shows that you are not immune, your healthcare professional may discuss vaccination after delivery. Postpartum vaccination can be compatible with breastfeeding, subject to your clinician's advice.
Prevention and early assessment are especially important in the third trimester because the timing of infection can affect decisions about maternal treatment and newborn care. A possible exposure does not guarantee infection, and appropriate medical advice can help clarify the next steps.