Chickenpox during pregnancy can sometimes affect a baby, but most babies exposed before birth are healthy. Infection early in pregnancy carries a small risk of a rare condition called congenital varicella syndrome, which can affect the skin, limbs, eyes, or brain. Infection close to delivery can be more dangerous because a newborn may develop serious chickenpox. The risk depends strongly on timing, and prompt medical care matters.
Chickenpox is a contagious viral infection caused by the varicella-zoster virus. Its effects on a developing baby depend largely on when the pregnant person becomes infected. An infection in early pregnancy may carry different risks from one that occurs shortly before birth. Knowing these differences can help families understand what medical monitoring may be needed and why it is important to contact a healthcare professional promptly after an exposure or the appearance of a rash.
How does the timing of chickenpox affect the baby?
The timing of infection is one of the most important factors when assessing the possible effects on a baby. Chickenpox in early pregnancy is associated with a small risk of abnormalities that develop before birth, while infection near delivery raises concern about chickenpox in the newborn. According to the Royal College of Obstetricians and Gynaecologists (RCOG), most babies are not harmed, although certain stages of pregnancy require closer assessment.
Chickenpox in the first or early second trimester
When chickenpox develops during the first trimester or early second trimester, there is a small risk of a rare condition called congenital varicella syndrome. This occurs when infection affects fetal development. It does not occur in every pregnancy affected by chickenpox, and most babies born after maternal infection are healthy.
According to the Centers for Disease Control and Prevention (CDC), congenital varicella syndrome can involve changes affecting several parts of the baby's body, including the skin, limbs, brain, and eyes. Other possible findings include low birth weight. The effects depend on the individual circumstances, and the condition is uncommon.
Possible features of congenital varicella syndrome include:
- Scarring or unusual marks on the skin.
- Underdevelopment or differences in the growth of an arm or leg.
- Eye abnormalities that may affect vision.
- Changes affecting brain development, including a smaller-than-expected head size.
- Poor growth before birth.
These are possible effects of the rare syndrome, not outcomes that should be expected in every pregnancy involving chickenpox. A healthcare professional considers the timing of infection, the pregnancy history, and any relevant examination or ultrasound findings when discussing the baby's individual risk.
Chickenpox in the middle of pregnancy
When infection occurs later in pregnancy but before the final weeks, the immediate concerns may be different. The virus can remain inactive in the baby's body and, in some cases, become active again later, causing shingles during childhood. This possibility does not mean that every exposed baby will develop symptoms or experience health problems.
There is also evidence of an association between chickenpox during the first half of pregnancy and a higher chance of preterm delivery, meaning birth before 37 completed weeks. MotherToBaby explains that this association is among the pregnancy-related concerns considered when reviewing varicella infection. The risk for an individual pregnancy cannot be determined from timing alone.
Chickenpox during the last four weeks of pregnancy
Chickenpox in the weeks leading up to birth creates a different concern: the baby may develop chickenpox around the time of delivery or shortly afterward. The RCOG identifies the last four weeks of pregnancy as a period when the risk of the baby catching chickenpox is highest. The infection can still occur earlier, but the risk of serious newborn illness is especially important when the maternal rash develops very close to birth.
The mother's immune system produces antibodies in response to infection. These antibodies can pass to the baby during pregnancy and help provide protection. However, if chickenpox develops just before delivery, there may be too little time for enough protective antibodies to reach the baby. This can leave a newborn more vulnerable to infection.
Why is chickenpox around delivery particularly concerning?
Chickenpox affecting a newborn is called neonatal varicella. It can be serious, particularly when the mother develops the rash from five days before delivery through two days after delivery. According to the CDC, this timing places the newborn at risk because protection from maternal antibodies may be inadequate.
Newborns have developing immune systems, so an infection that might be manageable in an older child can be more dangerous during the first days of life. Neonatal varicella may require hospital assessment, preventive treatment after exposure, antiviral medication, and close observation, depending on the circumstances.
Chickenpox infection in the mother does not automatically mean the newborn will become infected. However, when the rash develops close to delivery, the maternity and newborn teams need to know as soon as possible so they can assess the timing and decide whether additional precautions or treatment are needed.
Does chickenpox increase the risk of miscarriage or birth defects?
Miscarriage can occur for many reasons, and current evidence does not establish that chickenpox necessarily increases an individual's chance of miscarriage. The more clearly recognized fetal concern is the small risk of congenital varicella syndrome when infection occurs during early pregnancy. This distinction is important because exposure or infection alone does not establish that a pregnancy will have a poor outcome.
Birth defects also occur in pregnancies without chickenpox. When congenital varicella syndrome is a concern, the healthcare team can explain what is known about the infection at that stage of pregnancy, discuss the possible outcomes, and arrange appropriate assessment. Risk estimates differ among sources, and figures from groups of pregnancies cannot predict an individual baby's outcome.
What should you do after exposure to chickenpox during pregnancy?
If you are pregnant and have been in contact with someone who has chickenpox, contact your obstetrician, midwife, or other healthcare professional promptly if you have never had chickenpox or are unsure whether you are immune. Do not wait for a rash to appear before asking for advice.
The UK National Health Service (NHS) advises pregnant people who are unsure of their immunity and have been exposed to chickenpox to seek medical advice immediately. A blood test may help establish whether antibodies from a previous infection are present. This information helps the healthcare team decide whether preventive treatment or further assessment is appropriate.
If a chickenpox-like rash develops during pregnancy, contact your maternity team or healthcare professional urgently. Explain that you are pregnant and may have chickenpox before attending a clinic or hospital, because arrangements may be needed to reduce exposure to other pregnant people and newborns.
Depending on the circumstances, a clinician may consider antiviral medication or other preventive measures. The decision can depend on the timing of exposure, whether a rash has developed, your immunity, your stage of pregnancy, and your medical history. Do not start prescription antiviral medication or other treatments without professional guidance.
What monitoring might the baby need?
If chickenpox occurs during early pregnancy, the healthcare team may refer you to a fetal medicine specialist. Ultrasound scans can help assess aspects of the baby's growth and development. The team may discuss what an ultrasound can show, its limitations, and whether any additional tests are appropriate. Not every pregnancy affected by chickenpox requires the same monitoring plan.
When infection occurs close to delivery, the focus may shift toward planning safe care for the newborn. The obstetric and pediatric teams may review the date the rash began, the expected or actual delivery date, and the baby's exposure. Depending on the level of risk, they may recommend preventive antibodies, antiviral treatment, or close monitoring after birth.
These decisions are based on the clinical circumstances rather than on the presence of a rash alone. The purpose of assessment is to identify situations in which additional care may reduce the chance of serious illness and to provide appropriate follow-up for the baby.
When does chickenpox require urgent medical attention?
Chickenpox during pregnancy can also cause serious complications for the pregnant person, including pneumonia and, less commonly, inflammation affecting other organs. Contact a healthcare professional urgently if you develop a suspected chickenpox rash during pregnancy, even if you otherwise feel reasonably well.
Seek emergency medical care if you have difficulty breathing, significant chest symptoms, marked drowsiness or confusion, a severe or rapidly worsening illness, or other alarming symptoms. Vaginal bleeding during an illness also warrants urgent assessment. Do not delay care while trying to work out whether the infection has affected the baby.
Can chickenpox during pregnancy be prevented?
Avoiding exposure is particularly important if you have never had chickenpox and do not know whether you are immune. If you have been exposed, prompt medical advice can help establish your immunity status and determine whether preventive measures are suitable. Until you receive advice, avoid close contact with people who may have chickenpox and follow the healthcare team's instructions.
The chickenpox vaccine is a live vaccine and is not recommended during pregnancy. If testing shows that you are not immune, a healthcare professional can discuss vaccination after delivery to help protect against future infection. Vaccination planning should follow the advice applicable to your circumstances and local healthcare guidance.
The key point is that chickenpox during pregnancy does not mean a baby will be harmed. Early infection carries a small risk of problems with development, while infection immediately before or after birth raises particular concern about serious newborn chickenpox. If you have been exposed or develop a rash, prompt medical assessment allows the care team to evaluate the timing, establish whether you are immune, and plan any monitoring or treatment that may be needed.