Congenital Infections

Infections contracted before or at birth from the mother

  • Present from birth
  • Lifestyle as a risk factor depends on the cause
  • Gender and genetics are not significant factors

Most infections contracted by a mother during pregnancy do not affect the fetus, but some cross the placenta and cause harm. These infections are often minor illnesses for the pregnant mother, and she may not even be aware of them. Serious infections such as HIV (see HIV infection and AIDS) may also be passed on to the fetus.

The effect on the baby depends on the stage of pregnancy at which the infection occurs. In early pregnancy, the development of organs may be disrupted, and a miscarriage could occur. Infections in later pregnancy may result in premature labour and a baby who is seriously ill at birth. Infections may also be transmitted as the baby passes through the birth canal.

What are the causes?

In the first 3 months of pregnancy, the viral disease rubella can lead to fetal heart abnormalities (see Congenital heart disease) and impaired hearing and vision. Cytomegalovirus (CMV) infection and toxoplasmosis, which is caused by a protozoal parasite found in cats’ faeces or undercooked meat, may cause miscarriage or malformations of the fetus in early pregnancy. CMV is the leading cause of congenital deafness and toxoplasmosis can damage the retina (the light-sensitive cells at the back of the eye). Later in pregnancy, these infections may lead to premature labour, stillbirth, and serious illness in the newborn baby. Listeriosis, a bacterial infection that can be contracted from eating soft cheese and pâté, may cause miscarriage, stillbirth, or serious infection in the newborn baby.

Long-term viral infections that can be passed from mother to fetus include HIV infection and hepatitis B and C (see Acute hepatitis). The bacterial infection syphilis may also be passed on. These infections do not always produce symptoms at birth but can cause serious illness later in life.

Some infections can be transmitted from mother to baby during labour. Some of these infections, such as herpes simplex virus (see Genital herpes) and streptococcal bacteria, can be life-threatening in a newborn baby. The risk of contracting an infection is increased if the mother’s waters break prematurely (see Premature rupture of membranes).


The pale patches in this view of the retina at the back of a baby’s eye indicate the congenital infection toxoplasmosis.

What might be done?

If a baby is seriously ill at birth and a congenital infection is suspected, blood and urine samples are taken to identify the infection. Babies are usually nursed in a special care baby unit and treated intravenously with appropriate drugs. Ultrasound scanning may be used to image the baby’s brain and echocardiography may be arranged if there is a heart problem. In the UK, newborn babies at high risk of hepatitis B infection are routinely immunized against it. If the mother is known to be infected with hepatitis B, the newborn baby is given antibodies against the virus in addition to immunization.

Can they be prevented?

Women can minimize the risk of contracting many of these infections during pregnancy. For example, they can ensure they are immunized against rubella before starting a pregnancy. To avoid toxoplasmosis infection, pregnant women should avoid eating undercooked meat, wash their hands after handling raw meat or food contaminated with soil, and avoid contact with cat faeces (in cat litter, for example). Pregnant women should also avoid eating foods linked with listeriosis.

Pregnant women with HIV infection are monitored, and they may be prescribed antiviral drugs to keep them healthy and to reduce the risk of transmitting the virus to the fetus. In some cases, a caesarean section may be recommended for pregnant women with HIV or active herpes infection at the time of the birth.

Mild congenital infections may have no lasting effect on the baby, but severe infections can be life-threatening. Congenital abnormalities may also result in long-term health and learning problems.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

Back to top