Getting chicken pox during pregnancy is rare, but it carries real risks for both you and your baby. The specific dangers depend heavily on when in pregnancy the infection occurs. Most pregnant women who contract chicken pox recover fully, and the chance of serious harm to the baby is low, but the stakes are high enough that prevention and early treatment matter.
Risks to Your Health
Pregnancy changes your immune system in ways that make certain infections hit harder. Chicken pox is one of them. The biggest concern is varicella pneumonia, a lung infection that develops when the virus spreads beyond the skin. Symptoms include cough, shortness of breath, fever, and rapid breathing, typically appearing a few days after the rash starts. The CDC notes that pregnant women who develop chicken pox are at risk for serious complications, primarily pneumonia, and in some cases may die from the infection.
There’s been debate about whether the timing matters for maternal complications. Some studies suggest that pneumonia is more frequent and severe when chicken pox is caught in the third trimester, though other research hasn’t confirmed this. Regardless of trimester, any pregnant woman with chicken pox who develops breathing problems needs immediate medical attention. Intravenous antiviral medication is the standard treatment for pneumonia in this situation.
How Chicken Pox Can Affect the Baby
The risk to your baby depends almost entirely on when during pregnancy you’re infected. The three windows that matter are early pregnancy, late pregnancy, and the days immediately surrounding delivery.
First and Second Trimester: Congenital Varicella Syndrome
If you catch chicken pox during the first or second trimester, there is a small chance the virus crosses the placenta and causes a pattern of birth defects called congenital varicella syndrome. This is estimated to affect 0.4% to 2.0% of babies born to women who develop chicken pox during this period. The risk is highest between weeks 8 and 20 of pregnancy, and very low after week 20.
Congenital varicella syndrome can cause a range of problems. The most characteristic signs include skin scarring in distinctive patterns, shortened or underdeveloped limbs, a smaller than normal head size, loss of brain tissue in the outer layer of the brain, intellectual disability, and global developmental delays. Not every affected baby has all of these features, and the severity varies. After a chicken pox infection in early pregnancy, detailed ultrasound monitoring can look for some of these abnormalities, though not all signs are visible before birth.
Near Delivery: The Most Dangerous Window
The highest-risk scenario is developing chicken pox right around delivery. If the rash appears anywhere from 5 days before to 2 days after giving birth, the baby can be born with an overwhelming infection. Without antiviral treatment, the fatality rate in these newborns is as high as 30%. This happens because the baby is exposed to the virus but doesn’t receive enough of the mother’s protective antibodies, which take several days to develop after infection and cross the placenta.
When doctors know the mother has an active infection in this window, the newborn is treated immediately with antiviral medications and may also receive an injection of antibodies to help fight the virus. With prompt treatment, outcomes improve dramatically.
Treatment During Pregnancy
If you develop chicken pox while pregnant, antiviral medication can reduce the severity and duration of your illness. Current clinical guidelines recommend starting oral antiviral treatment within 24 hours of the rash appearing, particularly if you’re 20 weeks or further along. Treatment earlier in pregnancy is also considered on a case-by-case basis. The goal is to limit how much the virus replicates, which reduces both your symptoms and the potential viral load reaching the baby.
If you develop complications like pneumonia, treatment shifts to intravenous antivirals in a hospital setting. The earlier complications are caught, the better the outcomes tend to be. Any new cough or difficulty breathing during a chicken pox infection in pregnancy warrants urgent evaluation.
What Happens After Exposure
If you’re pregnant and not immune to chicken pox, and you’ve been in close contact with someone who has it, there’s a narrow window to act. An injection of varicella-zoster immune globulin (a concentrated dose of antibodies against the virus) can prevent or reduce the severity of infection. It works best when given as soon as possible after exposure but may still be effective up to 96 hours later. This treatment doesn’t guarantee you won’t get sick, but it significantly lowers the odds of a severe case.
You can’t receive the chicken pox vaccine during pregnancy because it contains a live, weakened form of the virus. If you’re already immune, either from a past infection or vaccination, you and your baby are protected. Most adults in the U.S. are immune, as roughly 90% of people have had chicken pox or been vaccinated by adulthood.
Vaccination Before Pregnancy
The simplest way to eliminate the risk is to confirm your immunity before getting pregnant. A blood test can check whether you have antibodies against the varicella virus. If you’re not immune, the vaccine is safe and effective, but you need to wait at least one month after each dose before trying to conceive. The vaccine requires two doses, so ideally this planning happens a few months before conception.
If you’re already pregnant and discover you’re not immune, vaccination has to wait until after delivery. In the meantime, avoiding contact with anyone who has chicken pox or shingles (which is caused by the same virus) is the best protective strategy. Household contacts who aren’t immune can also be vaccinated, since the vaccine doesn’t pose a risk to pregnant women living in the same home.