Parvovirus B19 (slapped cheek) in pregnancy

Slapped cheek syndrome, also called fifth disease, is caused by parvovirus B19. It is most often seen in primary-school-age children, who develop a bright red rash on the cheeks, sometimes followed by a lacy rash on the body. Many infections, including in adults, cause few or no symptoms.

The virus spreads through coughs and sneezes. People are most infectious before the rash appears, when they may only have a mild fever or runny nose, which is why exposure is often only recognised afterwards.

The NHS describes slapped cheek syndrome as highly infectious and says it can be harmful to the baby, although in most cases the baby is not affected. On the dedicated NHS page, the stated risk to a pregnant woman is a very small chance of miscarriage or other complications.

The reason is that the virus targets developing red blood cells. If it reaches the baby, it can in some cases cause anaemia in the unborn baby, which in the more severe cases leads to fluid build-up. Because that situation is uncommon and can be recognised on scans, the general approach is monitoring rather than alarm.

Many adults had the infection in childhood without noticing, and carry protective antibodies. The NHS pregnancy infections page says a blood test checks whether you are immune. If you are, the contact is of no concern for the baby.

The UKHSA guidance on viral rash in pregnancy sets out how clinicians should assess a pregnant woman after contact or a rash illness, including serology and onward referral. You do not need to read it, but it explains why you will be asked about the type and length of contact and the timing relative to your due date.

The NHS advises telling your midwife or a GP if you are pregnant and have been near someone with slapped cheek syndrome. The sooner the better, because the tests are most informative when they are taken in the right window after contact.

• Contact your midwife, GP or NHS 111 the same day or the next working day.

• Describe how close and how long the contact was and when it occurred.

• Say how many weeks pregnant you are and whether you have a weakened immune system or a blood disorder, which increase the importance of getting advice.

• Do not wait for a rash, since infection in adults often causes joint pain rather than a facial rash.

Adults with parvovirus may have a mild flu-like illness, a rash, and aching or swollen joints, particularly in the hands, wrists, knees and ankles. Joint symptoms can last days or weeks. Not everyone has all of these, and some people have no symptoms.

If you think you have slapped cheek syndrome and are pregnant, the NHS advises you to see a GP, because of the small risk of miscarriage or other complications. A blood test can confirm recent infection.

When recent infection is found, the maternity team will usually arrange regular ultrasound scans for several weeks to check the baby for signs of anaemia, and may refer you to a fetal medicine unit. If the baby is affected, specialist treatment is available in a hospital setting, and most pregnancies are managed without any intervention.

Most women who are infected go on to have a healthy baby. The exact schedule of scans and the length of follow-up depend on how many weeks pregnant you are and your local pathway.

There is no vaccine. Washing hands often, not sharing cups and cutlery, and avoiding close contact with children who have a fever and runny nose reduce the chance. By the time the cheek rash appears the child is generally no longer infectious, so keeping a child with the rash away from school is not necessary. If you work with children or in healthcare, ask your employer or occupational health about advice for pregnant staff. Report reduced baby movements to your maternity unit immediately, whatever the cause.