Infection in pregnancy may be transmitted to the neonate either by infection during intra-uterine life, or by infection during the process of birth. Babies are at risk of contracting hepatitis B or HIV, being damaged by rubella, the virus that causes German measles, or cytomegalovirus, being infected by herpes simplex virus if the mother has genital herpes and developing chlamydia infection (causing conjunctivitis) if the mother has chlamydia. Any genital infection can be passed to the baby during delivery - gonorrhoea causes a particularly unpleasant eye infection, called ophthalmia neonatorum - a term now used to describe any pussy discharge from the eyes of any neonate less than 21 days old. The herpes zoster virus which causes chickenpox can cause spontaneous abortion, so women who are exposed to chickenpox, and who have not had it themselves, need to be tested to see if they have antibodies are and if they haven't they need to be given some (called zoster immune globulin or ZIG). Maternal infection with listeria, which is found in products containing unpasteurised milk such as some soft cheeses and pates, can also cause miscarriage. The virus that causes slapped cheek syndrome in children can cause anaemia in a foetus, so children with this disorder should be kept away from women in late pregnancy. Toxoplasmosis, which may be contracted from cats, can cause foetal eye problems, so beware cat litter.

Babies born to mothers who are hepatitis B positive can be treated from birth in order to prevent them developing the disease, and subsequent liver damage. Babies born to mothers who are HIV-positive may benefit from early anti-viral treatment. Women who have genital herpes may secrete the virus during the course of the pregnancy; if the virus is found in the vagina before delivery it may be wiser to deliver the baby by Caesarean section in order to prevent the infant developing herpes encephalitis. Women with heavy vaginal discharge should have the cause identified if they are approaching delivery in order that any infectious agent can be eradicated.