There are a number of viruses that could potentially harm an unborn baby but the chance of coming into contact with them is very low.
The majority of pregnancies are unaffected by these harmful viruses and continue normally and healthily. You can have vaccinations to prevent the spread of some of the viruses that can be harmful to your baby. For example, the MMR vaccine is available to protect you and your baby against measles, mumps and rubella.
Chickenpox is caused a virus called varicella zoster. If you have chickenpox in the first 13 weeks of pregnancy there is a very small risk (about 1%) that the baby will develop eye problems, underdeveloped limbs or brain damage. The risk of these problems increases to about 2% if you catch chickenpox when you are 13-20 weeks pregnant.
If you have chickenpox after your 20th week of pregnancy, there is no risk that your baby will develop abnormally. However, if you catch chickenpox within a week before giving birth, the newborn baby may develop a severe form of chickenpox.
Most people suffer from chickenpox when they are a child, so about 90% of women are already immune by the time they are pregnant.
If you are pregnant and you develop chickenpox, or you have come into contact with someone with chickenpox and you are not sure if you are immune, you should speak to your GP or midwife immediately.
This is an infection caused by the virus parvovirus B19 and is also known as Slapped cheek syndrome, parvovirus infection, or Fifth Disease. Research shows that about 60% of all adults in the UK have been infected with this virus at some point. Like chickenpox, when you have had it once you are immune for life.
Most unborn babies are unaffected by exposure to parvovirus B19, but if you develop the infection in the first 20 weeks of pregnancy, there is an increased risk of miscarriage. If infection occurs in weeks 9-20 there is also a small chance that the baby will develop hydrops fetalis, a rare condition that can cause heart failure and anaemia. In about 50% of cases this can be fatal to the baby.
Measles is now rare in the UK as it is routinely vaccinated against in childhood. However, if a pregnant woman is affected by the measles virus, especially towards the end of her pregnancy, there is an increased risk of premature birth. If caught early in the pregnancy there is a higher risk of miscarriage and stillbirth.
If you are pregnant and you develop measles, or you have come into contact with someone with measles, it is important that you speak to your GP or midwife straight away.
German measles is also known as rubella and, like measles, it is extremely rare in the UK as is is vaccinated against in childhood. However, if you do suffer from German measles while you are pregnant, it can cause miscarriage, stillbirth, or birth defects such as brain damage, deafness, heart defects and cataracts.
You should speak to your GP or midwife urgently if you are pregnant and you develop rubella, or you have come into contact with someone who has rubella.
Colds and Flu
Colds and flu viruses are not harmful to an unborn baby, unless a secondary infection such as pneumonia develops which affects the health of the mother.
This is caused by a virus from the herpes family. About 1% of babies will catch this infection, but only 1 in 10 of these will develop any problems as a result. These problems can include learning difficulties, jaundice, swollen liver or spleen, or visual impairments.
Mumps is not known to cause problems for the unborn baby, but if caught during the first 12-16 weeks of pregnancy it can increase the risk of miscarriage. Like measles and German measles, mumps is also very rare in the UK because it is routinely vaccinated against in childhood.
If you are pregnant and you develop mumps, or you have come into contact with someone who has mumps, you should speak to your GP or midwife immediately.
Hand, Foot and Mouth Disease (HFMD)
This is an infection caused by the coxsackie A virus. There is normally no risk to the unborn baby if HFMD is caught during pregnancy. However, if you catch the virus close to the birth date, it can pass to the baby and they may need hospital treatment.
Genital warts are caused by the human papilloma virus (HPV). Genital warts might increase in size during pregnancy, making it difficult to go to the toilet and sometimes problems can arise during birth. The virus can sometimes cause the newborn baby to develop a condition called laryngeal papillomatosis, when warts grow inside the larynx or throat but this is very rare.