Page modified at: 14/03/2010
Viral Infections in Pregnancy
Although there are a number of viruses that are potentially harmful to an unborn baby, it is rare to come into contact with most of them. The majority of pregnancies are unaffected and proceed normally. Vaccination programmes, such as MMR (measles, mumps and rubella) also help to prevent the spread of some of the viruses that can harm an unborn baby.
How do viruses get passed to unborn babies?
Inside the womb, the blood supply of a mother and her foetus is linked. This means that not only do nutrients and oxygen pass to the baby, but so do both viruses and the antibodies to fight them.
If you become infected with most viruses - such as flu and chickenpox - during pregnancy, then they can be passed to your baby. Depending on your own natural immunities, the stage of development of the foetus, and the type of virus, this can sometimes be nothing to worry about, or may potentially have more serious effects.
Certain treatments are available to help try to prevent viruses being passed to the baby. If a mother carrying the hepatitis B virus has her baby immunised in the first few hours after birth, it may not develop the infection. Caesarean section or treatment with an antiviral medicine (aciclovir) may prevent the herpes simplex virus from being passed on to the baby of a pregnant woman who has genital herpes lesions.
Chickenpox is caused by the varicella zoster virus. If chickenpox is caught 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. If chickenpox is caught in weeks 13-20 of pregnancy the risk rises to about 2%.
If chickenpox is caught after 20 weeks, there does not appear to be any risk of abnormality to the baby. However, if chickenpox is caught within seven days before birth, the newborn baby may develop a severe form of chickenpox.
Most pregnant women (about 90%) are already immune to the chickenpox virus because they had the condition when they were a child.
If you are pregnant, and you develop chickenpox, or you have come into contact with someone with chickenpox, and you're not sure if you had chickenpox when you were a child, you should speak to your GP, or midwife, immediately.
Colds and flu
Colds and flu viruses should not have an effect on an unborn baby, unless a secondary infection, such as pneumonia develops, affecting the health of the mother.
Cytomegalovirus infection causes a 3% to 5% chance of having a baby with a birth defect. CMV is a member of the herpes family of viruses and is primarily a sexually transmitted disease but it can also be transmitted from mother-to-child congenitally through blood transfusions, by close personal contact and via organ transplantation. Cytomegalovirus (CMV) is caused by a virus from the herpes family of viruses. About 1 in 100 babies will catch this infection, but only 1 in 10 of these will develop any problems as a result. Potential problems can include learning difficulties, swollen liver, or spleen, jaundice, or visual impairments.
Human papilloma virus (HPV)
Genital warts are caused by a virus called the human papilloma virus (HPV). Genital warts can sometimes grow larger during pregnancy, making urination difficult, and sometimes causing problems during birth. In rare cases, the virus can cause the newborn baby to develop a condition called laryngeal papillomatosis, which is where warts grow inside the larynx (voice box), or throat.
Measles is now rare in the UK because it is routinely vaccinated against during childhood. However, if a pregnant woman does contract the measles virus, particularly towards the end of her pregnancy, her baby will be at increased risk of being born prematurely. Measles caught earlier in the pregnancy increases the risk of miscarriage and stillbirth.
If you are pregnant and you develop measles, or you have come into contact with someone with measles, you should speak to your GP, or midwife, immediately.
German measles (rubella)
German measles (also called rubella) can cause miscarriage, stillbirth, or birth defects, such as deafness, brain damage, heart defects, and cataracts. Like measles, rubella is now rare in the UK because it is routinely vaccinated against during childhood.
If you are pregnant and you develop rubella, or you have come into contact with someone who has rubella, you should speak to your GP, or midwife, immediately.
Mumps in pregnancy is not known to cause problems for the unborn baby, but it can increase the risk of miscarriage during the first 12-16 weeks of pregnancy. Like measles, and German measles, mumps is now rare in the UK because it is routinely vaccinated against during 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)
Hand, foot and mouth disease (HFMD) is an infection that is usually caused by the coxsackie A virus. There is normally no risk to the unborn baby if HFMD is caught during pregnancy. However, if the virus is caught shortly before birth, it can pass to the baby and, after birth, they may need hospital treatment to avoid developing further problems.
Parvovirus (Erythema infectiosum)
Parvovirus (also known as Erythema Infectiosum, slapped cheek syndrome, or fifth disease) is an infection that is caused by the parvovirus B19. Research suggests that up to 60% of all adults in the UK have been infected with this virus at some point. After you have been infected, it is likely that you will develop a life-long immunity to parvovirus B19.
Most unborn babies are unaffected by exposure to parvovirus B19, but if a pregnant woman develops the infection in the first 20 weeks of pregnancy, it increases the risk of miscarriage. As well as the increased risk of miscarriage, if infection occurs in weeks 9-20 there is also a small risk that the baby will develop hydrops fetalis. This is a rare condition that can cause heart failure and anaemia and can be fatal in about half of all cases.
Toxopalsmosis in pregnancy may cause the woman to have no, or just a few mild symptoms, such as a sore throat and a mild fever. However, there is a chance that the toxoplasmosis infection will be passed on to the baby. This is known as congenital toxoplasmosis and it can result in miscarriage and severe damage to the baby causing blindness and mental handicap.