...so women who are pregnant and come into contact with people who have this illness need to seek medical advice. What is slapped cheek disease? Slapped cheek disease is sometimes called fifth disease or erythema infectiosum. It is an infection caused by the parvovirus B19 virus. It most commonly occurs in children aged 3-15 years, but anyone can be affected. It is infectious (can be passed on). The infectious period is for 4-20 days before the rash appears. By the time the rash develops, it is usually no longer infectious. Scarlet Fever Scarlet fever is most common in children aged between two and eight, although anyone can catch it. It's caused by bacteria from the streptococcus (strep) group, which is the same group of bacteria that causes sore throats. Scarlet fever has a distinctive pink-red rash, which usually develops after a sore throat (strep throat) or skin infection (impetigo) caused by strep bacteria. There's no evidence that catching scarlet fever during your pregnancy will put your baby at risk. However, if you are infected when you give birth, there is a risk your baby may also become infected. Pregnant women who have been diagnosed with scarlet fever will be treated with antibiotics, which are safe to take in pregnancy and labour. What if I get a rash during pregnancy? If you develop a rash when you're pregnant, get advice from your GP or midwife straight away so they can diagnose its cause This advice has been taken from the NHS Website.