Fifth disease is a common childhood viral infection caused by human parvovirus B-19. It is also known as erythema infectiousum or "slapped cheek disease" because the facial rash resembles slap marks. Fifth disease is a mild airborne illness that can occasionally cause severe complications in pregnant women, though approximately half of all pregnant women are already immune due to prior exposure, the March of Dimes states.
Maternal Anemia
If Fifth disease occurs in the first half of pregnancy, a pregnant woman may develop anemia, a low red blood cell count that results from red blood cell destruction. Women with sickle cell disease, thalassemia or other diseases that affect red blood cells may become severely anemic and require transfusions.
Fetal Loss
Miscarriage or fetal loss occurs in approximately 15 percent of women with Fifth disease in the first half of pregnancy, and around 2 percent of pregnancies past 20 weeks gestation, the Society of Obstetricians and Gynecologists of Canada states. Multi-system organ damage may cause fetal loss.
Fetal Anemia
In most cases of Fifth disease in pregnant women, there are no harmful effects to mother or fetus. But in about one-third of cases, the virus crosses the placenta, destroying the red blood cells of the fetus and resulting in fetal anemia, the University of South Carolina School of Medicine explains.
Fetal Hydrops
Around 6 percent of fetuses infected with the virus die from fetal hydrops, a severe form of anemia that causes severe fluid retention and heart failure, the March of Dimes reports. Hydrops usually is seen 4 weeks after a pregnant woman contracts the infection, according to the University of South Carolina School of Medicine. Pregnant women who develop the infection a few weeks before delivery can also deliver babies suffering from fetal hydrops, Stanford University states. Fetal transfusions may reverse the anemia at the time of birth.
