Sample size and sampling techniqueThe sample size was determined using a single popula-tion proportion formula. As seroprevalence of antirubella antibody among pregnant women in Ethiopia is unknown, we assumed a 50% seropositivity rate, a 5% margin of error and 95% level of confidence. Further considering a 10% non-response rate, the sample size was calculated to be 422. Systematic random sampling method was used to recruit pregnant women attending the ANC clinics. Based on the hospitals’ plan and performance within 3months prior to the time of data collection, an esti-mated 845 pregnant women were expected to visit ANC of the two hospitals during the study period. This estimate was divided by the sample size to determine the sample interval (k-value), which would be 2. The first served pregnant woman and every second woman thereafter were invited to participate in the study until the required sample size was obtained. The desired number of study participants for each hospital was determined consid-ering their respective ANC coverage using proportionate sampling. The target recruitment at Adare Hospital and Hawassa University Comprehensive Specialized Hospital was calculated to be 286 and 136, respectively