Rubella is caused by the rubella virus. The virus is spread through droplets of moisture from the nose or throat of someone who is infected.
These droplets are released into the air when someone coughs, sneezes or talks.
If you inhale an infected droplet of moisture, you can get rubella. This can easily happen through face-to-face contact with someone who is infected, or from just being together in the same room.
Once you have had rubella then you normally develop a lifelong immunity against further infection.
Congenital rubella syndrome
If a pregnant woman who does not have immunity to rubella (either due to previous infection or vaccination) catches the rubella virus, then the virus can be passed on to her unborn baby.
The virus can disrupt the development of the baby, causing a series of birth defects that are known as congenital rubella syndrome (CRS).
The risk of CRS affecting the baby and the extent of the birth defects it causes depends on how early in the pregnancy the mother is infected. The earlier in the pregnancy the greater the risks.
If a woman catches rubella during the first 10 weeks of pregnancy then the chance of her baby being affected by CRS is as high as 90% and the baby is likely to experience multiple birth defects.
If a woman catches rubella between the 11th and 16th week of pregnancy then the risk of CRS occurring drops to around 10-20% and it is likely that CRS will only result in a single birth defect.
Birth defects are rare if an infection occurs after the 16th week. The most commonly reported birth defect (at least in the past when rubella was more common) caused by infection in later pregnancy is deafness.
