Human parvovirus B19 (Latin, parvo = poor), infection is also called "fifth disease" and occurs mainly in children. Pets (dogs and cats) have their own animal parvoviruses that do not infect humans. Parvovirus B19 (B19V) is the only member of the Parvoviridae family known to cause disease in humans. The term "fifth disease" arose due to this being the fifth in a group of once-common childhood diseases (the other four are measles, rubella, scarlet fever and Dukes' disease) that all have similar rashes.
Parvovirus B19 infection in a pregnant woman, followed by transplacental transmission to the fetus, can lead to miscarriage or hydrops fetalis. Parvovirus infects the fetal liver, the site of erythrocyte production during early development. The swollen appearance in hydrops is the result of severe anemia and perhaps also myocarditis, both of which contribute to congestive heart failure. Thrombocytopenia may accompany severe anemia. Seroprevalence data indicate that about half of pregnant women are susceptible to parvovirus infection.
...The estimated risk of transplacental infection among women who are infected with parvovirus B19 during pregnancy is 30 % , with a 5 - 9 % risk of fetal loss. Infection during the second trimester poses the greatest risk of hydrops fetalis. Parvovirus B19 probably accounts for 10 - 20 % of all cases of nonimmune hydrops fetalis.
... The risk of infection is highest in epidemic years and is correlated with the extent of contact the pregnant woman had with children.
Most parvovirus B19 infections during pregnancy do not lead to loss of the fetus."
"Usually there is no serious complication for a pregnant woman or her baby following exposure to a person with fifth disease. About 50 per cent of women are already immune to parvovirus B19, and these women and their babies are protected from infection and illness. Even if a woman is susceptible and gets infected with parvovirus B19, she usually experiences only a mild illness. Likewise, her unborn baby usually does not have any problems attributable to parvovirus B19 infection.
Sometimes, however, parvovirus B19 infection will cause the unborn baby to have severe anemia and the woman may have a miscarriage. This occurs in less than five per cent of all pregnant women who are infected with parvovirus B19 and occurs more commonly during the first half of pregnancy.
There is no evidence that parvovirus B19 infection causes birth defects or mental retardation.
There is no universally recommended approach to monitor a pregnant woman who has a documented parvovirus B19 infection. Some doctors treat a parvovirus B19 infection in a pregnant woman as a low-risk condition and continue to provide routine prenatal care. Other physicians may increase the frequency of doctor visits and perform blood tests and ultra-sound examinations to monitor the health of the unborn baby. The benefit of these tests in this situation, however, is not clear.
If the unborn baby appears to be ill, there are special diagnostic and treatment options available, and your obstetrician will discuss these options with you and their potential benefits and risks."
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