Chickenpox and pregnancy

Chickenpox is a highly contagious viral infection characterized by an itchy, blister-like rash. The infection is typically mild in healthy children, but it can cause more severe symptoms or complications in adolescents, adults and people of all ages who have weak immune systems. If contracted during pregnancy, chickenpox can cause severe symptoms and pose significant risks to both mother and baby.


Causes/associated factors
Chickenpox is caused by the varicella-zoster virus. About 85 percent of all chickenpox cases develop in children age 14 and younger. Although there have been rare cases of reinfection (more commonly in people who have weak immune systems), once you've had chickenpox you're considered immune for the rest of your life.
Chickenpox occurs most often during the winter and spring. In the United States, the greatest number of cases occur from March to May. Before the chickenpox vaccine was widely available, chickenpox led to at least 11,000 hospitalizations and 100 deaths each year in the United States.


The pregnancy factor
More than 90 percent of pregnant women are immune to chickenpox because they had the infection as children. In the United States, about four to seven women in 10,000 contract chickenpox during pregnancy.
If you develop chickenpox during pregnancy, here are the possible risks:

Some studies indicate that chickenpox contracted during pregnancy increases the risk of preterm labor.

If you develop chickenpox as an adult, you have a higher risk of developing pneumonia. You have the same risk of developing varicella pneumonia as other adults, but this type of pneumonia is more severe during pregnancy.

If you develop chickenpox during the first 20 weeks of pregnancy, your baby may be born with congenital varicella syndrome (a group of birth defects that can cause malformation of the limbs, scarring of the skin, and damage to the eyes and the brain). This condition affects up to 2 percent of babies whose mothers were infected with chickenpox during the first 20 weeks of pregnancy. In some cases, the baby may not survive.

If you develop the rash associated with chickenpox up to five days before through two days after delivery, your baby may develop neonatal chickenpox and become susceptible to chickenpox complications. Prompt treatment of the baby following birth can prevent or lessen the severity of the infection.

If you develop chickenpox from three weeks through six days before delivery, your baby may be born with chickenpox, but will usually not become seriously ill. Your baby will have had time before delivery to receive, via the placenta, antibodies (compounds that neutralize or destroy foreign substances in the blood) that you developed to fight the varicella virus.

Infants who have contracted chickenpox before birth are at risk of developing shingles (an infection caused by the same virus that causes chickenpox) in the early years of life.

Transmission
The incubation period (time from exposure until symptoms appear) averages 15 days but may last from 10 to 21 days. Chickenpox is contagious from about two days before the rash appears through about six days after, or as long as the sores aren't crusted over.
To develop chickenpox, the virus must enter your respiratory tract. Usually this occurs through contact with infected droplets coughed or sneezed into the air or passed from someone's hand. It can also occur after direct contact with the rash of a person infected with chickenpox or shingles. (After you unnoticed, it's often the time when you're most likely to infect others.

After the initial 24 to 48 hours, you'll develop an itchy rash that looks like flat red splotches. The rash may develop anywhere on your body, but usually begins on the scalp and moves to the trunk and then the arms and legs. It's often most noticeable on the trunk.

During the next stage, the flat red blotches develop into raised spots that look like small pimples. Eventually, these pimples fill with clear fluid and turn into blisters that look like drops of water on red bases. Your fever may be highest during this time.

Finally, the blisters break and form crusts. You may have intense itching when this happens, and your fever usually disappears. The crusts usually fall off somewhere between nine and 13 days after the rash appears. The entire cycle may repeat itself two to four times over the next two to six days. Symptoms are usually more severe in healthy adolescents and adults than healthy children. Symptoms may also be more severe in people who have weak immune systems.


Diagnosis
If you're unsure of your immunity to chickenpox or your medical history, blood tests can help your doctor determine if your body has produced antibodies (compounds that neutralize or destroy foreign substances in the blood) against the varicella virus. Blood tests can also be used if there's any uncertainty about the diagnosis. After known or possible exposure to chickenpox, diagnosis is most often based on the rash.
The baby may be tested for varicella antibodies through a cordocentesis (drawing blood from the umbilical cord), an amniocentesis (obtaining a sample of the fluid that surrounds the baby) or chorionic villus sampling (obtaining a sample of the tissue that attaches the sac that surrounds the baby to the uterus). In some cases, an ultrasound (using sound waves to create an image of the baby) may help the doctor determine the severity of the infection.


Treatment
If you've never had chickenpox and are exposed to someone who has it, contact your doctor right away. Your blood will be tested for antibodies to the varicella virus. If you're not immune to the virus, you may be given the varicella zoster immune globulin (VZIG), which contains varicella virus antibodies. VZIG may prevent you from getting chickenpox or make the infection less serious. It doesn't prevent infection in the baby. To be effective, it must be given within 96 hours of exposure to the virus. In some cases, antibody testing may not be done if it would delay the use of VZIG beyond 96 hours.
If you develop chickenpox five days before through two days after delivery, your baby has a high risk of serious illness and will also be given VZIG to help prevent infection.

The antiviral medication acyclovir may be prescribed if you develop a serious case of chickenpox or complications, such as pneumonia. Because the safety of acyclovir in pregnancy is uncertain, it's not used routinely for all women who develop chickenpox during pregnancy. Babies who develop chickenpox after birth will also be given acyclovir.


Complications
Complications are most common in adolescents, adults and people who have weak immune systems. Serious complications of chickenpox include secondary bacterial infections of the chickenpox sores with possible scarring, dehydration, pneumonia, encephalitis (inflam- mation of the brain), myocarditis (inflammation of the heart muscle), hepatitis (inflammation of the liver), nephritis (inflammation of the kidney) and blood clotting problems.
About 11 percent of adults infected with chickenpox develop pneumonia. If you're pregnant, your risk of developing varicella pneumonia is the same, but it can be more severe during pregnancy. The symptoms of pneumonia usually appear three to five days after the chickenpox infection and may include rapid breathing, cough, shortness of breath and chest pain. Contact your doctor immediately if you develop any of these symptoms.

Reye's syndrome is a rare complication today thanks to the widespread avoidance of giving aspirin to anyone age 19 or younger who has chickenpox.


Shingles
Again, shingles, also known as herpes zoster, is an illness caused by the same virus that causes chickenpox. Shingles is less common than chickenpox during pregnancy and poses less risk to you and your baby.
You can only develop shingles if you've already had chickenpox. Here's how it works: After the chickenpox infection, the virus can lodge inside the nerve cells near your spinal cord and cranial nerves (a part of the central nervous system called the dorsal root ganglion). The virus may be inactive for years. If it reactivates, you have shingles. The virus moves along the nerve pathways of your skin, eyes and ears, causing severe pain and a blistering rash.


Prevention
If you're pregnant and don't have immunity to chickenpox, avoid exposure to anyone who has chickenpox or shingles. There's currently no effective treatment to prevent spreading the infection to the baby.
Before conception, it's best to discuss pregnancy with your doctor. If you haven't had chickenpox or are unsure of your medical history, your doctor may recommend testing to determine your immunity. Up to 90 percent of women who have no known history of chickenpox are found to be immune. If you're not immune and not pregnant, your doctor may recommend the varicella vaccine to prevent a chickenpox infection during a future pregnancy. The American Academy of Pediatrics and the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices recommend avoiding pregnancy for one month after receiving the vaccine. The vaccine manufacturer recommends a three-month delay.

Since March 1995, when the vaccine was approved for use in the United States, there have been no reported birth defects in babies whose mothers received the vaccine during pregnancy. In conjunction with the vaccine manufacturer, experts at the Centers for Disease Control and Prevention have developed a registry for monitoring outcomes of varicella vaccinations received inadvertently during pregnancy. For more information, call (800) 986-8999.