Getting sick when you're pregnant can be a very scary situation. Not only do you feel ill, but you're also concerned that your sickness will hurt your baby. Fortunately, the average cold or stomach upset is nothing to worry about. But some illnesses need to be taken seriously, such as the parasitic infection toxoplasmosis and the viral infection hepatitis B. If these infections aren't treated properly and promptly, they can harm you and your baby. Fortunately, taking the proper steps to reduce the chance that you'll contract these illnesses is easy.

Pregnancy Infections: Hepatitis B
Hepatitis B is a viral infection that causes liver inflammation. The virus is spread by contact with blood or other bodily fluids from an infected person. You are at increased risk if you live with or are sex partners with an infected person, have multiple sex partners, or are a health-care worker. This virus can produce a number of distressing symptoms, including fatigue, nausea, and jaundice. Fortunately, most people recover completely.

However, about 5 to 10 percent of women who have had hepatitis B continue to carry the virus in their system and can pass it on to their babies. These lifelong carriers of the virus are at increased risk of developing severe liver diseases such as cirrhosis (hardening of the liver) and liver cancer.

About 20,000 babies are born each year to women who either carry hepatitis B due to past infection or get it for the first time during pregnancy. Without treatment, as many as 50 percent of these babies contract the virus, usually during labor and delivery. The risk is highest when a woman gets hepatitis during the third trimester or carries a particularly active form of the illness. Most infected babies become chronic carriers who face a high risk of serious liver disease as adults.

The CDC recommends that all pregnant women be screened for hepatitis B. If you carry the virus, there's an 85 to 95 percent chance that infection can be prevented in your baby if he receives immune globulin therapy and the hepatitis B vaccine within 12 hours of birth, and two more doses of the vaccine in the first six months of life. The CDC also recommends that all babies be vaccinated against hepatitis B. Your best defense against this virus is prevention: Avoid exposure to the virus, and get the vaccine, which is considered safe during pregnancy — especially if you have risk factors.

Pregnancy Infections: Toxoplasmosis
Though you may never have heard of it before, toxoplasmosis is one of the most common infections in the world today. A person gets infected with this parasite by eating undercooked meat or through contact with cat feces. It's particularly prevalent in populations without high standards of hygiene, or in places where people often eat raw or undercooked meat, such as France.

Because toxoplasmosis is symptomless or mimics a mild flu, most cases go undiagnosed. If you've had this parasite before, you don't have to worry about it, because you will have developed immunity. You can't pass it on to your unborn baby, and it's unlikely that it will give you any trouble. The parasite will simply drift around dormant as long as your immune system is functioning normally. If you're planning to conceive and don't know whether you've had toxoplasmosis, ask your health-care provider if you should have a blood test that can show whether or not you're immune. This test is not a routine pregnancy screening (unless you have symptoms of toxoplasmosis), because it can't distinguish a harmless past infection from an active new one.