This cross-sectional and questionnaire-based seroprevalance study was conducted from November 2011 to January 2012 at obstetrics and maternity hospitals affiliated with Shiraz University of Medical Sciences in Shiraz, the capital city of Fars province in southern Iran. A convenience sampling method was used. The sample size necessary for this study was 138 pregnant women, calculated with the formula z2
and assuming that P
90%, confidence level
95%, and error
5%. The prevalence of immunity level (90%) was extracted from earlier research that determined this to be the approximate rate of immunity in pregnant women against measles and rubella 
There were no exclusion criteria except for refusal to participate. Two major obstetrics and maternity hospitals (Hafez and Zeinabieh Hospitals) are affiliated with Shiraz University of Medical Sciences; most pregnant women in Shiraz seek prenatal care at these centers. Initially, three trained, experienced midwives explained the aims of the study to the women and completed the informed consent forms and questionnaires. A 10-mL blood sample was taken from each participant. Each woman was interviewed face to face privately, and blood samples were obtained separately from each of them at the obstetrics clinics at each of the two participating hospitals.
The questionnaire consisted of an introductory explanation about the aims of the study and the identity of the researchers, followed by questions regarding demographic and obstetric characteristics of the participants and their medical history. The content and face validity of the questionnaire were evaluated by expert opinion, and its reliability was calculated as 0.65 according to the Kuder-Richardson formula 20 (KR20).
Body mass index was calculated as weight (kg) divided by height per square meter (m2
). Pregnant women with a gestational age (documented by their last menstrual period or pelvic sonography) of up to 14 weeks, 14+1
to 28 weeks, and 28+1
weeks were categorized as being in their first, second or third trimester of pregnancy, respectively. Blood samples were transferred promptly to the virology reference laboratory of Shiraz University of Medical Sciences, with appropriate safeguards to maintain cold chain standards. Serum IgG level was measured with an enzyme-linked immunosorbent assay (ElISA) using Ig G single test-Varicell kit, for measles (G/M 1001) and for rubella (G 1026 ). There is some variation among different studies regarding the concentration of IgG antibodies that is considered to be protective against rubella or measles. Some studies consider the presence of rubella IgG antibodies ≥10 IU/mL to provide evidence of protection 
, but in our study and in accordance with the protocol used by the virology department of Shiraz University of Medical Sciences, we categorized IgG levels against rubella or measles in pregnant women into three groups: nonimmune (<9 IU/mL), equivocal (9–11 IU/mL) or immune (>11 IU/mL).
All data were entered to SPSS version 11.5 software (SPSS, Chicago, IL, USA). The accuracy of data entry was ensured by randomly selecting and checking completed questionnaires against their corresponding data in the SPSS software. Graphs were produced with Microsoft Office Excel 2007. Differences between immune and nonimmune groups in demographic and obstetric characteristics and history of medical diseases were determined with the nonparametric chi-squared or Fischer’s exact test as appropriate. Correlations of interval and nominal variables with anti-rubella and anti-measles IgG antibody levels were determined by the Pearson and Eta coefficients, respectively. Simultaneous correlation of the most important variables (P≤0.20) as independent variables and IgG level as the dependent variable was determined by forward logistic regression. P values less than 0.05 were considered significant.
The Ethics Committee of the Health Policy Research Center affiliated with Shiraz University of Medical Sciences approved conducting this study based on the protocol described in the patients and methods. We obtained written consent of all participants in this study. The content of consent forms was approved by Ethics Committee of the Health Policy Research Center and consisted of introductory brief explanation about aims and steps of this study, including 10 mL blood withdrawal of them, and identifications of interviewers for interviewees. The signed consent forms were kept in archive of records of this survey. All potential participants who declined to participate or otherwise did not participate were eligible for treatment (if applicable) and were not disadvantaged in any other way by not participating in the study.