These common diseases can be fatal for unborn babies if you contract them during pregnancy. But take a deep breath: The odds are definitely in your favor as long as you take the right precautions.

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While there's certainly no reason to panic over every little thing during pregnancy, some diseases are truly a cause for concern. Most can be avoided with proper hygiene habits like regular hand-washing and staying away from sick people, while some can be kept at bay with vaccinations that protect Mom and Baby at the same time. And of course, common sense measures like engaging in safe sex with one partner and avoiding drugs, alcohol, and no-no foods like raw fish are helpful measures, too.

An image of red and silver stethoscopes on a purple background.
Credit: Getty Images.

Keep reading for our comprehensive guide to diseases that can turn deadly during pregnancy to keep yourself informed and on the right track to a healthy birth.

Cytomegalovirus (CMV)

Most people who come down with this common respiratory virus don't even realize they're sick with anything more than a cold. But if you happen to become infected during pregnancy, it can spell disaster for your unborn baby.

Cytomegalovirus, or CMV as it's widely known, spreads through saliva, mucus, and other bodily fluids. Symptoms can include fever, sore throat, swollen glands, and fatigue, and it can cause life-altering and sometimes fatal complications in a fetus, like microcephaly, deafness, blindness, and even learning disabilities.

Sadly, the fatality rate of CMV in unborn babies is about 5 percent. According to Florencia Segura, M.D., FAAP, a pediatrician with Einstein Pediatrics, "CMV is the most common congenital viral infection. Every year, 20,000 to 40,000 infants are born with congenital CMV. It's way more common and just as dangerous as Zika virus but currently gets almost no media coverage."

STDs

Chances are, your doctor screened you for common sexually transmitted diseases during an early prenatal visit. That's because many STDs can be harmful to a fetus if you happen to be infected during pregnancy.

"Chlamydia can lead to things like preterm labor from premature rupture of membranes (PROM), as well as low birth weight," says Nikola Djordjevic, M.D., from MedAlertHelp.org. "Syphilis and Hepatitis C can both have similar effects, including the possibility of stillbirth. Other effects of STIs on baby can include pneumonia, blood infections, brain damage, and chronic liver disease."

The Flu

Getting a flu shot is a no-brainer since contracting the flu can have serious consequences during pregnancy. Aside from the fact that you may have more severe symptoms than your non-pregnant peers, the flu can increase the likelihood of premature labor and birth defects such as neural tube defects. If it's severe enough, influenza can even lead to fetal death.

Rubella

Rubella isn't one of the diseases during pregnancy that you hear much about. Even so, it's important to stay up-to-date on vaccinations, including the MMR (measles, mumps, and rubella) vaccine, to prevent transmission. That's because fetal exposure to the rubella virus can lead to life-long complications like heart defects, liver damage, and deafness, according to the Centers for Disease Control and Prevention (CDC).

Toxoplasmosis

If you're a soon-to-be mama with a cat, rejoice! You just got out of litter box duty for nine months. That's because cat feces often carries Toxoplasmosa gondii, a parasite that's exceptionally harmful to a developing fetus. Other ways to contract toxoplasmosis are through gardening and eating unwashed vegetables and fruits that have been in contact with fecal matter in soil. To avoid toxoplasmosis in pregnancy, take these precautions:

  • Avoid eating undercooked meat or unwashed fruit and vegetables.
  • Don't rub your eyes or face when preparing food.
  • Keep your cat inside so it doesn't come into contact with the parasite and never let your cat eat uncooked meat.
  • Ask another person to change the cat litter box. If you must clean the cat litter box, wear rubber gloves and wash your hands afterward.
  • Use work gloves when gardening and wash your hands afterward.
  • Keep your children's sandbox covered when not in use to prevent cats from using it as a litter box.

Dr. Segura estimates that there are roughly 400 to 4,000 cases of congenital toxoplasmosis in the United States each year, and "the spectrum of congenital toxoplasmosis includes seizures, blindness, intellectual disability, and death."

Listeriosis

It's definitely a good idea to steer clear of deli meat and soft, unpasteurized cheese during pregnancy, since these can increase your risk of contracting a type of food poisoning known as Listeria. Not only can Listeria lead to scary things like miscarriage and stillbirth, it can also infect an otherwise healthy baby at birth, possibly leading a severe bacterial infection like meningitis or sepsis. Treatment for neonatal listeriosis involves antibiotics, but there's still a rather high death rate among newborns who contract it.

The best way to prevent listeriosis is to avoid or use extra caution with foods that might be contaminated with the Listeria bacteria. The U.S. Department of Agriculture (USDA) and the FDA provide the following advice for pregnant women on

  • Do not eat hot dogs, luncheon meats, or deli meats unless they're heated until steaming hot.
  • Do not eat soft cheeses such as Camembert, feta, Brie, blue-veined cheeses, and Mexican-style cheeses such as queso blanco fresco.
  • Do not eat refrigerated paté or meat spreads. Canned or shelf-stable paté and meat spreads are safe to eat.
  • Do not eat refrigerated smoked seafood unless it is an ingredient in a cooked dish such as a casserole.
  • Do not drink raw (unpasteurized) milk or juice. Do not eat foods that contain unpasteurized ingredients.
  • Thoroughly wash all fresh fruits and vegetables before eating.
  • Because Listeria can grow even at refrigeration temperatures of 40 degrees or below, use all perishable items that are precooked or ready-to-eat as soon as possible and clean your refrigerator on a regular basis.

Zika

A relative newcomer to the list of scary diseases to avoid during pregnancy is Zika virus, which is transmitted to humans via mosquito bites. While not a widespread threat in North America, Zika outbreaks have occurred in regions of South and Central America, and it can also be contracted from sexual contact with an infected partner.

"Zika virus is a teratogen, which means it can cause birth defects such as microcephaly, limb contractures, seizures, developmental delay, and blindness," according to Laura Riley, M.D., obstetrician and gynecologist-in-chief at NewYork-Presbyterian and Weill Cornell Medicine.

In order to protect yourself against this dangerous disease, Dr. Riley advises parents-to-be to avoid traveling to areas with widespread Zika, to use bug spray with DEET if it can't be avoided, and to use condoms if your partner has traveled to Zika-prevalent areas.

Group B Strep

Group B streptococcus (GBS) is a common type of bacteria often found in the rectum or vagina. Pregnant women receive a GBS test between weeks 35 and 37 of pregnancy, which involves a quick swab of both areas. That's because GBS exposure can be deadly for a fetus or newborn. According to Group B Strep International, the bacteria can cause miscarriage, severe illness, or even death if contracted during birth.

"GBS most commonly causes infection in the blood (sepsis), the fluid and lining of the brain (meningitis), and lungs (pneumonia), [but can also cause] handicaps such as blindness, deafness, mental challenges, and/or cerebral palsy," says the Group B Strep International website.

Chickenpox

If you're not vaccinated against the chickenpox—and you've never had the viral infection— definitely get the jab prior to conceiving. That's because babies who are exposed to chickenpox in the womb, especially between weeks 8 and 20, have a small risk of congenital varicella syndrome. This does more than make your newborn itchy. Indeed, the Mayo Clinic indicates that your baby may suffer from skin scarring and abnormalities of the eyes, brain, limbs and gastrointestinal system. Also, if you get chickenpox shortly before delivery, your baby could develop neonatal varicella, which could be deadly. Finally, chickenpox increases your risk of pneumonia during pregnancy.

Fifth Disease

Fifth disease is a common childhood illness that you probably wouldn't have to worry about if you weren't pregnant. It's accompanied by mild respiratory symptoms and a "slapped cheek" appearance in otherwise healthy babies, and it's spread by infected droplets traveling through the air, similar to the cold or flu. The problem is that fifth disease, which is a strain of parvovirus, can be deadly to a developing fetus in some cases.

Luckily, there's only about a 30 percent chance of the virus affecting your baby, but complications are scary. "When the unborn fetus is affected, there's a 5-10 percent rate of fetal loss. The infection can lead to severe fetal anemia (decreased red blood cell counts), generalized swelling, congestive heart failure, myocarditis, and a condition called hydrops fetalis in which there is excessive fluid in multiple fetal body compartments which can also lead to fetal death," says Dr. Segura.