Fetal risk associated with rubella vaccination during pregnancy

Background: Costa Rica implemented a nationwide measles-rubella vaccination campaign among men and women (15-39 years old) in May 2001. A protocol was developed to follow-up the vaccinated women who were unknowingly pregnant, to determine the risk of congenital rubella syndrome (CRS) or congenital rubella infection only associated with the administration of the rubella vaccine RA27/3 during pregnancy. Methods: To classify the prevaccination maternal immune status, a serum sample was taken at the initial evaluation to detect IgM and IgG rubella antibodies (enzyme-linked inummosorbent assay). All pregnancies were followed up and all newborns were evaluated. A cord serum sample of their children was taken at birth. We calculated odds ratio, OR (95% confidence interval, 95% CI) associated with miscarriage, stillbirth, prematurity, low birth weight, and the presence of defects compatible with CRS. Results: The prevaccination immune status was established in 797 women and 1191 mother and child pairs were analyzed. Adjusted OR for miscarriage (OR = 0.60, 95% CI = 0.26-1.39), stillbirth (OR = 1.32, 95% CI = 0.10-16.81), prematurity (OR = 0.25, 95% CI = 0.03-2.39), low birth weight (OR = 0.25, 95% CI = 0.03-2.23) and defects compatible with CRS (OR = 1.09, 95% CI = 0.34-3.54) showed no association between immune and susceptible maternal status. There were no cases of CRS and no children were IgM positive. Conclusions: No adverse pregnancy outcome such as miscarriages or CRS was documented in women who were vaccinated and unknowingly pregnant. These results support RA27/3 rubella vaccine safety.