Up to 10% of women of childbearing age are still susceptible to Rubella infection, either because they were never vaccinated, a waning of immunity, or the vaccination failed.
Some 15-20% of young women, further, remain a potential source of routine antenatal screening.
Rubella infection during the first trimester of pregnancy is the greatest risk for foetal damage and traditionally was treated with a termination:
- 90% first 8 weeks (2 months)
- 50% third month
Risk from infection falls steeply after the first trimester, thereafter damage, if any, will be less severe:
- between 12-16 weeks: deafness has been reported!
- negligible after 16 weeks
Therefore, treat with great import any pregnant woman of a close contact who develops rubella-like symptoms:
- check rubella IgG and IgM (even if previously positive)
- paired sera
- if contact 2nd/3rd trimester, or rubella IgG positive in 1st trimester, further investigation is generally not necessary.