Seroepidemiology of Syphilis Infection among 2 Million Reproductive-age Women in Rural China: A Population-based, Cross-sectional Study.

Background:: Quantifying syphilis prevalence is important for planning interventions and advocating for resources on syphilis. However, data on large sample studies regarding the prevalence of syphilis among reproductive-age women in rural China were not available for analysis. The aim of the study was to determine the prevalence, epidemiological characteristics, and related factors of syphilis infection among reproductive-age women in rural China.

Methods:: Data were obtained from a nationwide, population-based, cross-sectional study under the National Free Preconception Health Examination Project which covered all the 31 provinces in Mainland China. Women intending to get pregnant within the next 6 months were enrolled between January 1, 2010, and December 31, 2012. Sociodemographic, gynecological and obstetric characteristics, and other relevant information were obtained through face-to-face interviews. Treponema pallidum particle agglutination assay test was used to detect positive samples of syphilis. Univariate and multivariate logistic regressions were performed to assess the associations between syphilis seropositivity and related factors.

Results:: The overall seroprevalence of syphilis (SPS) among the 2,044,126 women who received syphilis screening test during 2010-2012 was 0.37% (95% confidence interval [CI]: 0.36-0.37%). The SPS appeared 0.24% (95% CI: 0.23-0.26%) and 0.66% (95% CI: 0.59-0.72%) in women at 21-24 and 40-44 years of age, respectively, showing an increase of SPS, parallel with age, and the difference was significant. SPS was significantly higher in ethnic minorities than that in Han nationality (0.58% vs. 0.35%, respectively, odds ratio [OR] = 1.41, 95% CI: 1.30-1.53) and higher in workers than that in farmers (0.45% vs. 0.36%, respectively, OR = 1.27, 95% CI: 1.14-1.41). Women with primary school or below level had a higher SPS as compared to those with college or above educational level (0.61% vs. 0.32%, respectively, OR = 2.49, 95% CI: 2.14-2.89), and the increase reversely correlated with the levels of education. Women whose spouses were syphilis seropositive had significant greater risk (OR = 48.26, 95% CI: 44.38-52.48) as compared those whose spouses were seronegative. Women who reported having had a history of sexually transmitted infections were more likely to be tested positive for serological syphilis (OR = 27.17, 95% CI: 20.44-36.11) as compared to those without.

Conclusions:: High SPS is seen among reproductive-age women in rural China that calls for targeted interventions on syphilis prevention and control in this target population, with emphasis on those who are 35 years of age and above, less educated, being minor ethnicity, workers, and living in the western regions of China.