BMC Public Health 2006, 6:109 http://www.biomedcentral.com/1471-2458/6/109 able prevalence of 0.98% at 95% confidence interval width of 1–3 [11]. Each of the six clinics was supposed to enrol a minimum of 167 pregnant women. Participants The criteria for selecting pregnant women included all pregnant women aged between 15–49 years attending the ANC clinic for the first time during the current pregnancy during the surveillance period [11]. Routine investiga- tions for first time visits in these clinics, necessitates blood withdrawal. The exclusion criteria included pregnant women who had previously visited the clinic during the surveillance period, and those aged less than 15 years or over 49 years. Voluntary counselling and testing (VCT) for HIV among pregnant women has been routinely inte- grated into the reproductive and child health (RCH) clin- ics as part of the prevention of mother to child transmission (PMTCT) of HIV [19]. This routine is for hospitals designated to provide anti-retroviral treatment. We consecutively enrolled all counselled and consenting pregnant women attending antenatal clinics for the first time during the current pregnancy within the catchment area from November 2003 to April 2004. Ethical issues and investigations Both the Norwegian National Committee for Medical Research Ethics and the Tanzanian based National Insti- tute for Medical Research (NIMR) gave ethical approval. Respective health and government authorities at regional and district level received copies of the ethical approval, as required for the implementation of the study. At the indi- vidual level, an oral informed consent was sought after detailed explanation of the purpose and benefits of sur- veillance for participation in the research only. It seemed necessary to reveal the establishment of the PMTCT unit at the hospital and its potential benefits unrelated to refusal or participation in the research. Data collection tools and testing Questionnaires used for interviews had been translated into Swahili and translated back to English again to con- firm their meaning. Information collected included basic demographic details and knowledge on HIV modes of transmission. Respondents were asked to agree or disagree with 10 statements regarding HIV related knowledge based on the protective effect of condoms, VCT and PMTCT, including main modes of infection and risky behaviour. An index was developed to sum up the scores of each statement, thus each correct response scored "one" and the highest score was 10. It was necessary and func- tional to collaborate with the hospital PMTCT team. The PMTCT team performed counselling and registered names with codes. They provided the codes for questionnaires and kept the identifiers from the research team for research purposes. The research team conducted inter- views to consenting and counselled women using the codes. Screening for anti-HIV IgG antibody was per- formed anonymously for all blood samples collected for routine syphilis testing using Bionor HIV-1 & 2 assay® (BIONOR AS, Skien, Norway). Ice coolers were used to pack blood collected at ANC clinics and transported to the HLH laboratory for testing. Bionor HIV 1& 2 assay ® con- firmatory test was used to confirm all samples that tested positive on screening. We linked the results of the test back to questionnaires using codes, but identities of indi- viduals remained anonymous to the research team. Posi- tively confirmed results by codes were submitted to the PMTCT team, which proceeded with the required proce- dures for PMTCT as required by the national HIV treat- ment guidelines [19]. Statistical analysis Statistical analysis utilised STATA 8.0 [20]. Chi-square test was used to test bivariate associations for categorical asso- ciations of HIV infection and other associated factors. Where appropriate, we used Fisher's exact test. A logistic regression model was used to explore the association of socio-demographic and other variables with HIV infec- tion. Variables with p-values < 0.25 on univariate analysis and after assessment of co-linearity were included in the mul- tivariable model [21]. Variables included in the full mul- tivariable model that were not significant were dropped after assessment of interaction. We did not find any inter- action terms and the final reduced model was adjusted for age and residential area. These were history of genital sores and discharge, contraceptive use, number of sexual partners, age at first pregnancy, ever VCT and ever-used condom. We present odds ratios (OR), and 95% confi- dence interval (CI) for factors associated with HIV infec- tion. Results By the end of the surveillance period, 1377 pregnant women aged between 15 to 49 years were included. Of these, 41% were from remote hard to reach areas and the rest from other rural stratum. Among those enrolled, 4% (58/1377) refused to give blood for syphilis testing despite counselling and 2% (25/1377) of the blood sam- ples were haemolysed before testing resulting in a partici- pation of 94% (1296/1377). Examination of socio- demographic characteristics did not disclose significant differences between the participants and those who refused HIV testing. The mean age of the studied population was 26.3 (SD ± 6.09) Table 1 presents general characteristics of the study population. The prevalence of HIV was 2.0% (95%CI: 1.24–2.76). Pregnant women residing in the rural areas Page 3 of 9 (page number not for citation purposes)