Pregnant women who develop ‘slapped face syndrome’ have a 30 percent chance of passing it onto their unborn baby and during the first trimester the risk of fetal complications is heightened, says a new review published in BJOG: An International Journal of Obstetrics and Gynaecology.
‘Slapped face syndrome’ is caused by a virus called parvovirus B19. The virus blocks the development of red blood cells and induces inflammation forming the characteristic facial rash. Transmission of the virus is by respiratory droplets for example sneezing and coughing. The incubation period ranges from 4-14 days after exposure but may be as long as three weeks. A rash appears on the face and can also be seen on hands, wrists and knees.
Up to 50% of pregnant women are susceptible to the virus, however, only a small percentage of them will be infected with it. If a pregnant woman develops the virus, there is a 30% chance of fetal transmission, with a 5-10% rate of feta loss, though most neonates are born healthily. However, during epidemics, there is a greater risk of mother to child transmission.
Pregnant women who are particularly vulnerable are those who have weaker immune systems or who suffer from pre-existing haematological conditions. In addition, infected foetuses where there is tissue inflammation and red-cell destruction, are particularly at risk.
While the maternal symptoms of the virus are usually short-lived, the fetal complications that can occur include hepatitis, severe anemia, inflammation of the heart muscle, cardiac failure and fetal death.
The risk of fetal death is linked to gestational age at infection. Approximately 3% of first trimester miscarriages may be due to the virus. However this may differ between epidemic and non-epidemic periods.
Maternal infection in the first trimester is associated with a risk of fetal death of 19%. A gestational age of 13-20 weeks is associated with a 15% chance of fetal death and this falls to 6% after 20 weeks. In the third trimester, fewer fetal complications occur because there is a decreased need for a high number of red blood cells and their life span increases.
There is no specific antiviral therapy or vaccine available for parvovirus B19 infection. It is therefore important that obstetricians are familiar with the diagnosis and management of the infection, says the review. Diagnosis includes detection of developing heart failure, which can be assessed by detecting the accumulation of fluid in the baby using ultrasound scanning. Management can include transfusing the baby to correct anaemia, using very thin needles to introduce the blood into the baby’s circulation while it is still in the womb.
The review concludes that further research is needed to develop antiviral therapy and a future vaccine for the virus.
Professor Ronnie Lamont, from the National Institute of Child and Human Development, part of the National Institutes of Health (NIH) in the US and lead author on the review said:
“Our review highlights the seriousness of the parvovirus B19 infection and recommends how it is best treated. Once diagnosed, steps should be taken to reduce the risk of onward transmission. Frequent hand washing is an effective measure and infected persons should avoid crowded areas, such as schools or shopping centres, which are likely to be frequented by pregnant women.
“All pregnant women who know they have been exposed to the virus should have a blood test to tell whether they are susceptible, and if so, whether they are developing the infection. The facial rash can often be misdiagnosed as measles or rubella so the key is to think of this virus as a possible diagnosis in such cases. A simple blood test will make the diagnosis.
If a fetus is infected, regular ultrasound scans should be done to detect fetal anaemia and cardiac failure. Luckily if the infection occurs later than 30 weeks gestation, it is unlikely there will be any complications.”
Professor Philip Steer, BJOG editor-in-chief added:
“Parvovirus B19 infection is widespread and relatively harmless for the mother, but can have serious consequences in a small percentage of babies, especially if the infection is in the first or second trimester. This review will help clinicians recognise the virus and raise awareness of its diagnosis and management.
“The development of a vaccine would be extremely valuable and would prevent the significant number of fetal complications associated with the virus.”
Lamont R, Sobel J, Vaisbuch E, Kusanovic J, Mazaki-Tovi S, Kim S, Uldbjerg N, Romero R. Parvovirus B19 infection in human pregnancy. BJOG 2010;
Source: BJOG: An International Journal of Obstetrics and Gynaecology