Q: If I catch something from my sick toddler, can it affect my unborn baby?

A: Among the many changes that occur during pregnancy, the maternal immune system down-regulates to allow us to carry DNA that is different from our own. This lessens the chance that we will reject our unborn babies but increases our chances of contracting infectious diseases.

Common infections that cause mild to moderate disease in healthy adults and children can cause serious complications to both mother and baby if acquired during pregnancy.

Some illnesses can be transmitted from mother to unborn child. Two common infections that can be transmitted from a mother to her unborn child are cytomegalovirus, or CMV, and parvovirus B19. These common infections can be associated with moderate to severe fetal and infant complications when acquired during pregnancy.

CMV is the most common congenital infection, occurring in up to 2 percent of all newborns. The annual cost of treating the permanent disabilities and complications caused by CMV infections in the United States is estimated to be nearly $2 billion.

CMV that crosses the placenta presents the most significant risk to the fetus. CMV resulting from exposure to infected cervical secretions or breast milk typically has no symptoms and is not associated with severe outcomes.

If the mother is having a primary CMV infection, the overall risk of transmission to the fetus is approximately 30 to 40 percent.

These affected infants can have severe neurological consequences.

Infection in adults can be hard to detect because it often has no symptoms.

Parvovirus B19 produces a viral rash and is also known as fifth disease. Children typically demonstrate a facial rash, sometimes similar in appearance to a slapped cheek, in addition to possible fever, body rash and joint pain.

Most adult infections are mild and asymptomatic.

Parvovirus is generally transmitted by respiratory droplets and hand-to-mouth contact.

People are usually infectious five to 10 days after exposure, before the onset of the rash or other symptoms, and are no longer infectious by the time the rash appears.

After exposure to acute parvovirus B19 infection during pregnancy, rates of maternal-to-fetal transmission range from 17 to 33 percent.

Although most cases of fetal infection resolve spontaneously with no adverse outcomes, fetal parvovirus B19 has been associated with miscarriage, fetal anemia and stillbirth.

The rate of fetal loss among women with parvovirus B19 infection ranges from 8 to 17 percent before 20 weeks of gestation, to 2 to 6 percent after 20 weeks of gestation.

If your pediatrician is suspicious that your toddler has one of these viral infections, you should contact your OB-GYN immediately.

Dr. Joanne Williamson is an obstetrician-gynecologist at Memorial Health University Physicians, Provident OB/GYN Associates in Okatie.