Screening for potential susceptibility to rubella in an antenatal population: A multivariate analysis.

Rubella causes disease in the fetus. Immunity to rubella is therefore, routinely screened in pregnant women. In this retrospective observational study, we assessed the levels of potential susceptibility to rubella in the population of a north London antenatal clinic. Risk factors for potential susceptibility to rubella and changes in potential susceptibility to rubella over time were studied. Almost all women were screened for potential susceptibility to rubella (99.8%). The majority were predicted to be immune (96.8%). Women booking in later years within the study period showed higher levels of potential susceptibility to rubella. Booking during each subsequent year in the study gave women an odds ratio of 0.91 (CI:0.84, 0.98, P = 0.009) of being predicted to have immunity against rubella. Age was associated with predicted immunity to rubella, with a 5.1% (CI:3.3%, 6.9%, P < 0.001) increased likelihood for every year older. Previous pregnancy was predictive of immunity against rubella with an odds ratio of 1.41 (CI 1.21, 1.61, P = 0.001). Those from a non-white ethnicity were less likely to have antibodies predictive of immunity (OR: 0.730, CI: 0.581, 0.879 P < 0.001). Country of birth was associated with differences in potential susceptibility, with those being born outside of the British Isles having an odds ratio for predicted immunity of 0.63 (CI:0.35,0.91, P = 0.001). Being born in a high-risk country for rubella non-immunity was also a risk factor, giving an odds ratio of predicted immunity to rubella of 0.55 (CI:0.32, 0.77, P < 0.001).