rubella virus is a single - stranded ribonucleic acid virus of the togaviridae family [ 1 , 2 ] , and is a sole member of the genus rubivirus . infection with rubella virus occurs by inhalation of contaminated droplets , and can be vertically transmitted to fetuses during maternal infection leading to congenital infection . in addition , infection with rubella virus in adults may cause severe inflammation and pain in the joints . however , infection with rubella virus during the first trimester of pregnancy can lead to prematurity , low birth weight , miscarriage , stillbirth , and congenital rubella syndrome [ 6 , 8 ] . this syndrome is characterized by fetal anomalies including mental retardation , heart defects , cataracts , blindness , deafness , and hepatomegaly and jaundice . however , rubella outbreaks in japan and other countries have been reported recently [ 2 , 5 , 11 ] . the seroepidemiology of rubella virus infection in mexican populations has been scantily studied . an 87% seroprevalence of anti - rubella antibodies in puerperal women from delicias city in the northern mexican city of chihuahua was reported , whereas a 92.6% seroprevalence of rubella virus infection in pregnant women in two zones of the valley of mexico was found . in a study in leon , guanajuato , mexico , researchers found a 71% seroprevalence of rubella in 176 women at reproductive age . to the best of our knowledge , there is not any study on the seroepidemiology of rubella virus infection in pregnant women in northern mexico . therefore , this study was aimed to determine the seroprevalence of rubella virus infection in pregnant women in the northern mexican city of durango , mexico . furthermore , rubella seroprevalence association with the socio - demographic , clinical and behavioral characteristics of the pregnant women was also assessed . we performed a cross - sectional study using stored serum samples from a previous survey of cytomegalovirus infection in pregnant women in durango city , mexico . samples were originally obtained to determine the seroprevalence of anti - cytomegalovirus antibodies in pregnant women attending a public primary health care center ( clinic of family medicine , institute of security and social services of state workers ) in durango city , mexico . inclusion criteria for enrollment of the participants were : 1 ) pregnant women attending prenatal care ; 2 ) aged 15 years and older ; 3 ) residence in durango city ; and 4 ) who voluntarily accepted to participate in the survey . we obtained the socio - demographic , clinical and behavioral characteristics from the participants with the aid of a questionnaire . socio - demographic items included age , birthplace , residence , educational level , occupation and socio - economic status . clinical items included health status , history of lymphadenopathy , frequent headaches ; impairments of memory , vision and hearing ; and history of blood transfusions . in addition , the obstetric history ( month of pregnancy , number of pregnancies , deliveries , cesarean sections and miscarriages ) from each participant was recorded . behavioral items included foreign traveling , alcohol consumption , tobacco use , and washing hands before eating . sera were examined for anti - rubella igg antibodies by a commercially available enzyme - linked fluorescent assay ( elfa )  vidas rub igg ii  kit ( biomerieux sa , marcy - letoile , france ) and for anti - rubella igm antibodies by a commercially elfa anti - rubella igg antibody levels of  15 iu / ml were considered as a cut - off for seropositivity . this study was performed using stored serum samples from a previous survey . in such previous study , the purpose and procedures of the study were explained to all participants , and a written informed consent was obtained from all of them and from the next of kin of minor participants . the ethical committee of the institute of security and social services of state workers in durango city , mexico approved this study . results were analyzed with the aid of the epi info version 7 and spss version 15.0 software . for calculation of the sample size , we used a value of 15,000 as a population size from which the sample was selected , a reference seroprevalence of 87.0%   as expected frequency of the factor under study , 5.0% of confidence limits , a design effect of 1.0 , one cluster , and a confidence level of 95% . we evaluated the association between the characteristics of the women and rubella seropositivity by using bivariate and multivariate analyses . for comparison of the frequencies among groups , the pearson s chi - square and the fisher exact test ( when values were less than 5 ) were used . as a strategy to include variables in the multivariate analysis , we selected only variables with a p value equal to or less than 0.05 obtained in the bivariate analysis . we calculated the odds ratios ( ors ) and 95% confidence intervals ( cis ) by multivariate analysis using the enter method . we performed a cross - sectional study using stored serum samples from a previous survey of cytomegalovirus infection in pregnant women in durango city , mexico . samples were originally obtained to determine the seroprevalence of anti - cytomegalovirus antibodies in pregnant women attending a public primary health care center ( clinic of family medicine , institute of security and social services of state workers ) in durango city , mexico . inclusion criteria for enrollment of the participants were : 1 ) pregnant women attending prenatal care ; 2 ) aged 15 years and older ; 3 ) residence in durango city ; and 4 ) who voluntarily accepted to participate in the survey . we obtained the socio - demographic , clinical and behavioral characteristics from the participants with the aid of a questionnaire . socio - demographic items included age , birthplace , residence , educational level , occupation and socio - economic status . clinical items included health status , history of lymphadenopathy , frequent headaches ; impairments of memory , vision and hearing ; and history of blood transfusions . in addition , the obstetric history ( month of pregnancy , number of pregnancies , deliveries , cesarean sections and miscarriages ) from each participant was recorded . behavioral items included foreign traveling , alcohol consumption , tobacco use , and washing hands before eating . sera were examined for anti - rubella igg antibodies by a commercially available enzyme - linked fluorescent assay ( elfa )  vidas rub igg ii  kit ( biomerieux sa , marcy - letoile , france ) and for anti - rubella igm antibodies by a commercially elfa  vidas rub igm  kit ( biomerieux sa , marcy - letoile , france ) . anti - rubella igg antibody levels of  15 iu / ml were considered as a cut - off for seropositivity . this study was performed using stored serum samples from a previous survey . in such previous study , the purpose and procedures of the study were explained to all participants , and a written informed consent was obtained from all of them and from the next of kin of minor participants . the ethical committee of the institute of security and social services of state workers in durango city , mexico approved this study . results were analyzed with the aid of the epi info version 7 and spss version 15.0 software . for calculation of the sample size , we used a value of 15,000 as a population size from which the sample was selected , a reference seroprevalence of 87.0%   as expected frequency of the factor under study , 5.0% of confidence limits , a design effect of 1.0 , one cluster , and a confidence level of 95% . we evaluated the association between the characteristics of the women and rubella seropositivity by using bivariate and multivariate analyses . for comparison of the frequencies among groups , the pearson s chi - square and the fisher exact test ( when values were less than 5 ) were used . as a strategy to include variables in the multivariate analysis , we selected only variables with a p value equal to or less than 0.05 obtained in the bivariate analysis . we calculated the odds ratios ( ors ) and 95% confidence intervals ( cis ) by multivariate analysis using the enter method . their mean age was 29.17  5.96 years ( range 15 - 43 years ) . anti - rubella igg antibodies were found in 271 ( 97.1% ) of the 279 pregnant women examined . of the socio - demographic characteristics of the pregnant women , the variables including age group and socioeconomic status were associated with anti - rubella igg antibodies by bivariate analysis , whereas the variables including birthplace , residence , educational level , and occupation did not associate with anti - rubella igg antibodies . unemployed : none occupation , student or housewife . employed : employee , professional , business , or other . with respect to clinical characteristics , rubella seroprevalence was significantly ( p = 0.02 ) higher in pregnant women with frequent headaches , whereas women with history of deliveries had a higher ( borderline significance : p = 0.05 ) rubella seroprevalence than women without this history . other clinical characteristics of women including history of lymphadenopathy , impairments of memory , vision and hearing ; history of blood transfusions , month of pregnancy , number of pregnancies , deliveries , cesarean sections and miscarriages did not show an association with rubella seroprevalence by bivariate analysis . concerning behavioral characteristics of women , the variable  national trips  showed a borderline ( p = 0.05 ) association with rubella seroprevalence . other behavioral characteristics including traveling abroad , alcohol consumption , tobacco use , and washing hands before eating did not show an association with rubella seroprevalence . multivariate analysis of socio - demographic , clinical and behavioral variables with p values  0.05 by bivariate analysis including age , socioeconomic status , frequent headache , number of deliveries , and national trips showed that seroreactivity to rubella was positively associated only with national trips ( or = 7.39 ; 95% ci : 1.41 - 38.78 ; p = 0.01 ) , and negatively associated only with age ( or = 0.26 ; 95% ci : 0.06 - 0.99 ; p = 0.04 ) . very little is known about the serological status against rubella virus in pregnant women in mexico . therefore , this study aimed to determine the seroprevalence of igg and igm antibodies against rubella virus in pregnant women in the northern mexican city of durango . results indicate that 97.1% of the pregnant women studied had protective (  15 iu / ml ) antibodies against rubella virus infection . in mexico , although the majority of pregnant women tested had protective antibodies , nearly 3% of women were susceptible to rubella . this figure seems low but considering that there are nearly 40,000 births a year in durango state ( http://cuentame.inegi.org.mx/monografias/informacion/dur/poblacion/dinamica.aspx?tema=me&e=10 ) , thus there are about 1,200 pregnant women susceptible to rubella virus just in this mexican state . concerning studies in mexico , the seroprevalence of rubella found in the present study is higher than the 87% seroprevalence of rubella in early puerperium women in the northern mexican city of delicias , chihuahua , the 92.6% seroprevalence of rubella in pregnant women from iztapalapa and nezahualcoyotl areas in the valley of mexico , and the 71% seroprevalence in women of reproductive age in leon , guanajuato . however , this comparison should be taken with care since these studies were performed in different years and laboratory tests used were different from the tests we used . previous seroprevalence studies in mexico were performed from 1993 to 2004 . in those years , the coverage of rubella vaccination was lower than the one in the recent years . we used elfa to detect igg antibodies against rubella virus , whereas in the previous studies , the hemagglutination inhibition method [ 13 , 14 ] was used . in addition , we studied pregnant women in the urban city of durango , whereas rural and urban women were enrolled in the study in delicias , chihuahua . in an international context , the seroprevalence of rubella in pregnant women in durango is higher than the 93.1% seroprevalence of rubella found in pregnant women seen in a tertiary hospital in zaria , nigeria , and 87.5% seroprevalence in pregnant women in osogbo , nigeria   using enzyme - linked immunosorbent assays . similarly , our prevalence is higher than the 85.8% seroprevalence reported in pregnant women in southern italy using a microparticle enzyme immunoassay . the rubella seroprevalence found in our study is comparable with the 95.1% seroprevalence of rubella reported in pregnant women in sudan , the 93.3% seroprevalence in pregnant women in portugal , the 94.4% seroprevalence in pregnant women in oslo , norway , and 95.4% seroprevalence in women of childbearing age in venezuelan yupka indigenous communities . we found that seroreactivity to rubella was positively associated with national trips and negatively associated with age . however , it is possible that rubella exposure occurs also by national trips as results of the present study suggests . therefore , traveling to high endemic rubella regions should be avoided by pregnant women . in the present study , this study has limitations including a small sample size , and enrollment of women in only one clinic of family medicine . further studies with larger sample sizes and in several clinics to determine the seroprevalence of rubella in mexican communities should be conducted . rate of rubella immunity in pregnant women in the northern mexican city of durango is high . risk factors associated with rubella seropositivity found in this study may be useful for optimal design of preventive measures against rubella and its sequelae . rate of rubella immunity in pregnant women in the northern mexican city of durango is high . risk factors associated with rubella seropositivity found in this study may be useful for optimal design of preventive measures against rubella and its sequelae .
backgroundthe seroepidemiology of rubella virus infection in pregnant women in northern mexico is largely unknown . 
 we sought to determine the seroprevalence of rubella virus infection in pregnant women in the northern mexican city of durango , mexico . 
 seroprevalence association with the socio - demographic , clinical and behavioral characteristics of the pregnant women was also investigated.methodsthrough a cross - sectional study , we determined the seroprevalence of igg and igm anti - rubella virus in 279 pregnant women ( mean age 29.17  5.96 years ; range 15 - 43 years ) attending in a clinic of family medicine using enzyme - linked fluorescent assays . 
 a questionnaire was used to obtain the socio - demographic , clinical and behavioral characteristics of the pregnant women . 
 the association of rubella seropositivity and characteristics of the women was assessed by bivariate and multivariate analyses.resultsanti-rubella igg antibodies (  15 iu / ml ) were found in 271 ( 97.1% ) of the 279 pregnant women examined . 
 none of the 279 pregnant women were positive for anti - rubella igm antibodies . 
 multivariate analysis of socio - demographic , clinical and behavioral variables showed that seroreactivity to rubella virus was positively associated with national trips ( or = 7.39 ; 95% ci : 1.41 - 38.78 ; p = 0.01 ) , and negatively associated with age ( or = 0.26 ; 95% ci : 0.06 - 0.99 ; p = 0.04).conclusionsrate of rubella immunity in pregnant women in the northern mexican city of durango is high . 
 however , nearly 3% of pregnant women are susceptible to rubella in our setting . 
 risk factors associated with rubella seropositivity found in this study may be useful for optimal design of preventive measures against rubella and its sequelae .