Many people don't experience symptoms of a hepatitis B infection (HBV), which is why all moms are tested for HBV during pregnancy or when they arrive at the hospital for delivery.[1] If you're expecting and think you might have come into contact with HBV, it's important to talk to your doctor right away.

It's possible to pass the virus on to newborns during delivery through blood and feces, which can lead to serious complications — but nearly all cases of HBV in babies can be prevented with several shots starting as soon as possible after birth. 

What is hepatitis B?

Hepatitis B is a liver infection caused by the HBV virus. While some people who are infected with HBV only have a short-term (acute) infection that lasts for several weeks, for others it can lead to a serious lifelong chronic illness and can cause liver cancer.

Fortunately, there's a vaccine for HBV and getting it as soon as possible after exposure to the virus no matter your age prevents nearly all HBV infections.

What causes hepatitis B?

Hepatitis B is caused by the HBV virus, which is transmitted through body fluids like semen or blood. It can spread from a mom to her baby during birth, through sex with an infected person or via exposure to an infected person's saliva or blood (by sharing a toothbrush, razor or needle, for example).  

The vaccine is the best way to prevent infection. It's been around for decades, which means there's a good chance you were vaccinated as a child. If you're not sure, a blood test can tell you whether you're immune to the virus.

What are the signs of hepatitis B (HBV)?

Up to half of all adults and older kids as well as most kids under 5 who are infected with HBV have no symptoms (although they can still spread the virus to others). When symptoms do occur, they usually appear about three months after exposure. 

Symptoms of HBV include: 

  • Jaundice (yellow skin or eyes)
  • Fatigue
  • Abdominal pain
  • Nausea
  • Vomiting
  • Loss of appetite 
  • Dark urine
  • Clay-colored stool
  • Joint pain

The only way to know for sure if you're infected with HBV is to get a blood test. The CDC recommends all expecting people get tested for HBV during pregnancy or at the hospital.

How common is hepatitis B (HBV)?

An estimated 862,000 people in the United States and 257 million people worldwide have chronic HBV, according to the Centers for the Disease Control and Prevention (CDC).[2] In 2018, nearly 22,000 people are thought to have caught the virus, although only 3,322 cases were reported to the CDC.

Who is most at risk for hepatitis B (HBV)?

Anyone exposed to body fluids of an infected person is at risk of an HBV infection. You're at at increased risk for HBV if you: 

  • Are a health care worker (or work at any job where you're exposed to blood)
  • Have sex or live with someone who has HBV
  • Inject drugs or share needles or other drug equipment

What should you do if you test positive for hepatitis B during pregnancy?

Let your practitioner know right away if you think you've been exposed to HBV and haven't been vaccinated. Most newborns who are infected with HBV go on to have lifelong infections — but a series of shots starting within 12 hours of birth can prevent virtually all HBV infections in babies.

If a mother tests positive for hepatitis B, further tests are usually performed to see if it is an active disease. Active disease can mean that there are higher levels in the blood. A viral load can be performed to give exact levels, and if it is very high, a liver specialist may recommend antiviral medications to bring the level down and decrease risk of transmission. 

If you do test positive for HBV during pregnancy, your baby will get a dose of HBV immune globulin (known as HBIG) at birth as well as three rounds of HBV vaccinations. (All babies usually receive three doses of hepatitis B vaccine in total, including one shot right after birth.) In addition to a second shot at 1 to 2 months old, babies who are at risk of HBV infection get their third shot when they're about 6 months old. They then get tested for HBV after their final shot and again between 9 to 12 months to ensure that the vaccine worked and they haven't been infected with the virus. This vaccine series should protect your little one from the HBV virus for life. 

If you are infected with HBV, you should be able to safely breastfeed your baby, but it's important to work with a lactation consultant. If your nipples are cracked or bleeding, you should temporarily stop nursing until your nipples fully heal (but express and discard your breast milk to keep up your supply).[3]