Compare HIV/syphilis infections between age groups and explore associated factors of HIV/syphilis co-infections among men who have sex with men in Shenzhen, China, from 2009 to 2017.

The aim of this study is to assess the HIV/syphilis epidemic among men who have sex with men (MSM) aged <50 years and ≥50 years in Shenzhen, and explore the associated factors of HIV/syphilis co-infections among MSM in Shenzhen, in order to help prevention and intervention programs determine their target sub-group. A serial cross-sectional study was conducted on MSM in Shenzhen city, China from 2009 to 2017. A questionnaire was used to collect demographic characteristics, history of HIV testing, history of blood donation and sexual behaviors. 5 ml of venous blood were collected for syphilis and HIV tests. The overall prevalence of HIV, syphilis, HIV/syphilis co-infection was 9.40%, 18.97%, and 4.91%, respectively. The prevalence of HIV (15.26%), syphilis (27.71%), HIV/syphilis co-infection (9.24%) in aged ≥50 years MSM was significantly higher than aged <50 years MSM (9.15%, 18.59% and 4.72%, respectively). The following factors were found to be significantly associated with HIV/syphilis co-infections (P<0.05): age≥50 years (OR = 1.78, 95% CI = 1.10-2.87), high school or lower (OR = 1.49, 95% CI = 1.10-2.01), monthly income ≤436.2 USD (OR = 1.74, 95% CI = 1.25-2.42), monthly income 436.4-727.2 USD (OR = 1.46, 95% CI = 1.05-2.03), ≥2 anal sex partners in the past 6 months (OR = 1.59, 95% CI = 1.02-2.49), ≥2 oral sex partners in the past 6 months (OR = 1.60, 95% CI = 1.08-2.36), inconsistent condom use during anal sex in the past 6 months (OR = 1.50, 95% CI = 1.11-2.03). We found that aged <50 years and ≥50 years MSM in Shenzhen had a high prevalence of HIV/syphilis infection in a period from 2009 to 2017. Age-specific sexually transmitted diseases education, prevention, and intervention programs for aged ≥50 years MSM should be implemented urgently and integrated interventions of both HIV and syphilis infections on MSM are needed in the future.

Correction: Population-based study of chlamydial and gonococcal infections among women in Shenzhen, China: Implications for programme planning.

[This corrects the article DOI: 10.1371/journal.pone.0196516.].

Population-based study of chlamydial and gonococcal infections among women in Shenzhen, China: Implications for programme planning.

This study was aimed to estimate the prevalences of chlamydia (CT) and gonococcal (NG) infections and explore risk factors associated with the CT infection among women in Shenzhen, China. We collected socio-demographic and clinical data from women (aged 20-60) and determined positivity of CT or NG by nucleic acid amplification test (NAAT) with self-collected urine specimens. We estimated prevalence of CT and NG and determined risk factors associated with CT infection. Among 9,207 participants, 4.12% (95% confidence interval [CI], 3.71%-4.53%) tested positive for CT and 0.17% (95% CIs, 0.09%-0.25%) for NG. Factors significantly associated with CT infection included being an ethnic minority (ethnicity other than Han China) (Adjusted odds ratio [AOR], 1.9; 95% CI, 1.2-3.0), using methods other than condom for contraception (AOR, 1.5; 95% CI, 1.2-1.8), having a history of adverse pregnancy outcomes (AOR, 1.4; 95% CI, 1.1-1.8), and experiencing reproductive tract symptoms in the past three months (AOR, 1.3; 95% CI, 1.0-1.7). we found that CT infection is prevalent among women in Shenzhen, China and associated with both demographic and behavioral factors. A comprehensive CT screening, surveillance and treatment programme targeting this population is warranted.

Risk of Congenital Syphilis (CS) Following Treatment of Maternal Syphilis: Results of a CS Control Program in China.

Background: Early screening for syphilis among pregnant women and the effective treatment of maternal syphilis is fundamental to prevent congenital syphilis (CS). Methods: We obtained data from the Shenzhen Program for Prevention of CS (SPPCS) and estimated incidence rates of CS among infants born to syphilis-seropositive women treated with different regimens or untreated for maternal syphilis. Results: A total of 4746 matched cases of syphilis-seropositive mothers and their infants were included for analyses, and 162 infants were diagnosed with CS, providing an overall incidence of 3.41% (95% confidence interval [CI], 2.91%-3.98%). Among infants born to syphilis-seropositive women who had syphilis and were adequately treated before pregnancy, the incidence was 0.22% (95% CI, .05%-.66%). There were 159 cases of CS occurring in 3519 infants born to women who were syphilis-seropositive during their pregnancies, for an incidence of 4.52% (95% CI, 3.84%-5.28%). The incidence of CS was 1.82%-11.90% lower among infants born to the women treated with early benzathine penicillin G (BPG) compared with those treated with late BPG (adjusted odds ratio [aOR], 8.06 [95% CI, 2.93-22.21]; P < .001), other antibiotics (aOR, 7.71 [95% CI, .86-69.28]; P = .068), or those untreated (aOR, 68.28 [95% CI, 29.64-157.28]; P < .001). The incidence rates were 0.22% (95% CI, .06%-.80%) and 0.59% (95% CI, .35%-1.02%) in infants born to women treated with 2 courses and 1 course of BPG, respectively, corresponding to a risk difference of 0.37% (aOR, 1.74; 95% CI, .37-8.26). Conclusions: Treatment of syphilis-seropositive pregnant women with 1 course of intramuscular BPG before 28 gestational weeks is critical for prevention of CS.

HPV infections among MSM in Shenzhen, China.

BACKGROUND: An increasing incidence of anal cancer among men, especially men who have sex with men (MSM) suggests a need to better understand anal human papillomavirus (HPV) infection among this group. METHODS: A cross-sectional study was conducted among MSM in Shenzhen, China. Blood was collected for HIV serological testing and syphilis serological screening, and anal swabs were collected for HPV genotyping. Difference of HPV prevalence between HIV seropositive and HIV seronegative MSM was assessed by chi-square test. Factors associated with anal canal HPV infection were assessed by univariate and multivariate logistic regression. RESULTS: A total of 408 MSM were recruited. HIV and HPV prevalence were 6.9% and 36.4%, respectively. HPV was detected in the anal canal in 71.4% of the HIV-positive MSM and in 33.8% of the HIV-negative MSM (P<0.001). Oncogenic types were seen more often in anal specimens of HIV-positive MSM than in specimens of HIV-negative MSM (P = 0.001). The HPV genotypes detected most frequently were HPV06 (8.2%), HPV16 (7.2%), HPV11 (6.4%), HPV18 (4.7%), HPV58 (4.7%), and HPV52 (4.2%). CONCLUSIONS: In this study, HIV positive MSM had a higher burden of HPV infection, especially oncogenic HPV infection. HPV types 52 and 58 were as popular as those types designed for the currently available vaccine (HPV6, 11, 16, 18).

Reduction in mother-to-child transmission of syphilis for 10 years in Shenzhen, China.

BACKGROUND: Untreated maternal syphilis can result in the fetuses being infected. Severe adverse pregnancy outcomes include stillbirth, perinatal death, low birth weight, and congenital syphilis (CS). The World Health Organization has already classified global elimination of CS as a priority. However, this preventable disease is still threatening people's health in the world. METHODS: A Programme of Prevention of Mother-to-Child Transmission of Syphilis in Shenzhen was launched in 2002. All pregnant women in Shenzhen were screened for syphilis by serological methods at their first prenatal care visit. The infected individuals were treated with 3 weekly injections of 2.4 million units of benzathine penicillin. The babies were followed up until 18 months old to diagnose CS. RESULTS: Up to 2011, the Programme of Prevention of Mother-to-Child Transmission of Syphilis in Shenzhen screened 2,077,362 pregnant women and intervened in 7668 mothers infected with syphilis. The screened rate among pregnant women increased from 89.8% in 2002 to 97.4% in 2011. The proportion of those having adverse pregnant outcomes (including spontaneous abortion, premature delivery, and stillbirth) decreased from 27.3% in 2003 to 8.2% in 2011. The incidence of CS decreased from 115/100,000 in 2002 to 10/100,000 (live births) in 2011. CONCLUSIONS: In 2002, in the face of rising CS numbers, Shenzhen adapted a syphilis control program that involved cost-free testing for pregnant women, commitment and collaboration at multiple levels of the health system, and strong supervision and government guidance. Local program and surveillance data suggest that the program has been very successful in reducing CS incidence.

Risk factors for congenital syphilis and adverse pregnancy outcomes in offspring of women with syphilis in Shenzhen, China: a prospective nested case-control study.

BACKGROUND: Despite existence of a highly effective intervention, maternal syphilis still causes substantial perinatal morbidity and mortality, even in China, where antenatal health services are strong. This study sought to address personal, programmatic, and other risk factors for congenital syphilis (CS) and adverse pregnancy outcomes (APOs) among pregnant women in Shenzhen, China. METHODS: Pregnant women attending antenatal services were offered serologic tests, and those diagnosed as having syphilis were recruited from April 2007 to October 2012. In a nested case-control study for the pregnancy outcomes of syphilis-infected women, we assessed risk factors comparing infants born with CS (group II) and with any APOs (group III) to infants without CS or APOs (group I). RESULTS: During the 66-month study period, we screened 279,334 pregnant women and identified 838 (0.3%; 95% confidence interval, 0.28%-0.32%) women infected with syphilis. Among infants born to syphilitic mothers, 8.2% (34/417) were diagnosed as having CS and 24.7% (103/417) were diagnosed as having APOs. Compared with group I, maternal baseline titers of nontreponemal antibodies (adjusted odds ratio [aOR], 2.13), stage of syphilis (aOR, 21.56), length of time between the end of the first treatment to childbirth (aOR, 11.93), gestational week at treatment (aOR, 2.63), and fathers' cocaine use (aOR, 15.44) and syphilis infection status (aORpositive vs. negative, 5.84; aORunknown vs. negative, 5.55) were positively associated with CS, but prenatal care (aOR, 0.11) and complete treatment (aOR, 0.20) were negatively associated with CS. Maternal age (aOR, 1.43), marriage (aOR, 2.41), history of cocaine use (aOR, 3.79) and ectopic pregnancy (aOR, 5.91), baseline titers of nontreponemal antibodies (aOR, 1.30), stage of syphilis (aOR, 8.89), length of time between the end of the first treatment to childbirth (aOR, 2.52), gestational week at treatment (aOR, 1.78), and fathers' syphilis infection status (aORunknown vs. negative, 2.02) were also positively associated with APOs, but maternal history of syphilis (aOR, 0.44), prenatal care (aOR, 0.29), and complete treatment (aOR, 0.25) were negatively associated with APOs, CONCLUSIONS: Syphilis was an important cause of pregnancy loss and infant disability, particularly among women who did not receive prenatal care or had late or inadequate treatment. These study results can inform antenatal programs on the importance of early syphilis testing and prompt and appropriate treatment. Some strategies targeted at other risk factors areas may be helpful.

[Primary drug resistance of HIV-1 infected men who have sex with men in Shenzhen, China].

OBJECTIVE: To evaluate the status of drug resistance among treat-naive HIV-1 infected men who have sex with men (MSM) in Shenzhen during the period of 2008 - 2010. METHODS: Plasma samples of 227 treatment-naive HIV-1 infected MSM were collected in Shenzhen. HIV-1 pol genes (RT and PR) were amplified by nested-polymerase chain reaction (PCR) from RNA. Phylogenetic and drug resistance analyses were performed on the nucleotide sequence data. RESULTS: A total of 164 pol gene sequences were amplified. The prevalence of primary genotypic drug resistance was 14.6%. The overall prevalence of drug-resistant mutations was 22.6%, corresponding to 8.54% for protease inhibitors (PI) minor drug resistance mutation, 1.22% for nucleotide reverse transcriptase inhibitors (NRTI) drug resistance mutation and 13.41% for non-nucleotide reverse transcriptase inhibitors (NNRTI) drug resistance mutation. The prevalence of drug-resistant mutations was 30.88% for CRF01_AE strain and 19.23% for B strain. CONCLUSION: The prevalence of drug resistance is relatively moderate in the treat-naive HIV-1 infected MSM in Shenzhen. The prevalence of drug-resistant HIV-1 among MSM in Shenzhen should raise a high alert.

[Study on the molecular-epidemiological characteristics of HIV-1 in Shenzhen, 1992-2008].

OBJECTIVE: To investigate the epidemiological characteristics of HIV-1 subtype in Shenzhen from 1992 to 2008. METHODS: 489 HIV-1 positive plasma samples were collected from 1992 to 2008 in Shenzhen. HIV-1 env genes were amplified by nested-PCR from RNA. Phylogenetic analysis was performed on data regarding the nucleotide sequence. RESULTS: A total of 464 sequences were amplified and genotyped. Data from this study revealed that CRF01_AE was a predominant HIV-1 subtype in Shenzhen (64.4%, 299/464), followed by subtypes CRF_BC (17.5%, 81/464), B' (14.7%, 68/464) and B (2.4%, 11/464). Subtype C (0.4%, 2/464), A1 (0.2%, 1/464), CRF02_AG (0.2%, 1/464) and CRF06_cpx (0.2%, 1/464) were also prevalent in Shenzhen. CRF01_AE and CRF_BC were predominant among heterosexuals, homosexuals and injection drug users, while B' was predominant among blood donors. Results from phylogenetic tree analysis showed that some of the HIV-1 clusters had been defined in CRF01_AE strains at different time or groups with different transmission routes. Cross-infections were also seen. CONCLUSION: CRF01_AE was the predominant HIV-1 subtype in Shenzhen while CRF_BC, B, B', C, A1, CRF02_AG and a small amount of CRF06_cpx or recombinant subtypes were prevalent in this city. Different subtypes showed great variation in the process of epidemics.

Molecular epidemiology of genital Chlamydia trachomatis infection in Shenzhen, China.

OBJECTIVE: To investigate molecular epidemiology of Chlamydia trachomatis infection among patients recruited from different clinic settings in Shenzhen, China. METHODS: A total of 2534 patients from the sexually transmitted disease (STD) clinics, obstetrics and gynaecology (OBGYN) clinics and genitourinary medicine (GUM) clinics in 34 hospitals participated in the study. The C trachomatis infection was determined using COBAS Amplicor system. DNA extracted in C trachomatis-positive samples was amplified using a nested PCR based on ompA gene and then genotyped using a microsphere suspension array. RESULTS: The overall prevalence of genital C trachomatis infection was 17.7%. The prevalence in patients at STD or GUM clinics was significantly higher than that in patients at OBGYN clinics. Being male (adjusted OR (AOR) 2.5, 95% CI 1.8 to 3.4), having no consistent use of a condom with casual partners in the past 3 months (AOR 1.7, 95% CI 1.1 to 2.8) and having any STD symptoms (AOR 3.3, 95% CI 2.0 to 5.4) were independently associated with C trachomatis infection. Eight genotypes were identified. The most prevalent genotypes were F (22.3%), E (22.0%) and D/Da (12.7%). Other genotypes were G/Ga (8.0%), J (7.3%), K (2.7%), H (2.7%) and I/Ia (0.4%). Eighty-two samples (18.3%) were infected with multiple genotypes. Genotype D/Da among patients from GUM clinics was more common than those from STD or OBGYN clinics. Infections with genotypes G and F were statistically associated with abnormal vaginal discharge (p=0.001) and being married (p=0.014), respectively. Infection with multiple genotypes was more common among patients with a higher income (p=0.011). CONCLUSION: A substantial prevalence of genital C trachomatis infection in Shenzhen suggests the importance of detection and treatment of the infection in high-risk groups.

Prevalence of anorectal Chlamydia trachomatis infection and its genotype distribution among men who have sex with men in Shenzhen, China.

To investigate the prevalence and genotype distribution of Chlamydia trachomatis infection among men who have sex with men (MSM), 145 MSM from two sauna settings in Shenzhen, China were invited to participate in this study during September 2008 and May 2009. Anorectal swab and urine samples were collected and tested for chlamydial infection, and positive samples were genotyped. The prevalence of anorectal chlamydial infection was 24% in the study population and was significantly associated with proctitis symptoms. Up to 50% of the anorectal infections were asymptomatic. The most prevalent genotypes were G (39%) and D (37%), followed by J (11%). Genotypes related to lymphogranuloma venereum were not found in the study population. The high prevalence of anorectal infection in MSM suggests the importance of detecting and treating the infection in this population.

[Spatial and temporal patterns of primary and secondary syphilis in Shenzhen, China].

OBJECTIVE: To learn the spatial and temporal patterns of primary syphilis and secondary syphilis in Shenzhen and to provide evidence for carrying out further research on syphilis. METHODS: Primary syphilis and secondary syphilis cases among residents in Shenzhen between 2005 and 2009 (n = 11 303) were geocoded at street office level (n = 55) based on residence at the time of diagnosis. Both spatial and space-time scan statistics were used to identify clusters of street office by using SaTScan software. RESULTS: In the purely spatial analyses, clusters were seen in the junction of the Baoan district and Nanshan district (Xinan, Xixiang, Nanshan and Nantou street office) and in the region near Hong Kong (Dongmen, Shekou, and Futian street office), as well as in the other streets where entertainment industry was relatively developed (Longhua, Huafu, Huangbei and Cuizu street office). The clusters had not changed much in the first four years, but nine clusters appeared in 2009. Annually, the most likely clusters were located in Longhua (2005, P ≤ 0.001, RR = 3.34), Bamboo (2006, P ≤ 0.001, RR = 9.59), Huafu (2007, 2008 years, P ≤ 0.001, RR values were 4.18 and 4.75) and Cuizu (2009, P ≤ 0.001, RR = 8.02). In the space-time scan analysis, we found 16 significant clusters, which were similar to the pure spatial analyses. However, regional difference were also found, with the most likely cluster was the Guiyuan street office in 2006. CONCLUSION: Spatial and space-time scan statistics seemed to be effective ways in describing the circular disease clusters. We have had a better understanding on spatial and temporal patterns of primary syphilis and secondary syphilis in Shenzhen through spatial and space-time scan statistics of syphilis surveillance data in the recent years. The changes of spatial and temporal patterns of primary syphilis and secondary syphilis were also described by SaTScan software, which also provided useful reference for the preventive strategies on sexually transmitted diseases as well as on HIV. Useful information was also provided for financial investment and cost-effective studies.

Congenital syphilis: refining newborn evaluation and management in Shenzhen, southern China.

INTRODUCTION: Consistent definitions of congenital syphilis are critical for determining true incidences and setting up targets of elimination. This study aimed to assess the evaluation and management of infants at high risk of congenital syphilis with an antenatal syphilis-screening programme in the Shenzhen SEZ and to develop feasible definitions for the detection of congenital syphilis in China. METHODS: A retrospective study was conducted of all standardised records of pregnant women with positive syphilis between 2003 and 2007. Infants at high risk of congenital syphilis were evaluated by laboratory tests at birth and longitudinal follow-up. A screening test-positive congenital syphilis case was defined based on a positive 19S-IgM-FTA-ABS result at birth. Assuming that 19S-IgM-FTA-ABS was the gold standard, the sensitivity and specificity of the ascertainment methods were calculated. RESULTS: During the study period, 1010 live infants were born to women with active syphilis during pregnancy. 19S-IgM-FTA-ABS detected 42 screening-positive congenital syphilis cases and another nine cases were identified by longitudinal follow-up only. Using 19S-IgM-FTA-ABS as the gold standard, 'fourfold rapid plasma reagin (RPR) titres' had the highest sensitivity and specificity compared with the other two follow-up methods. DISCUSSION: 19S-IgM-FTA-ABS makes congenital syphilis case classification simpler and faster for newborns. In areas where 19S-IgM-FTA-ABS is not available, comparing newborn RPR titres with maternal titres can be an alternative method. Meanwhile, positive follow-up results act as treatment indicators for older infants. As congenital syphilis definitions vary over the country, the Shenzhen programme suggested a practical model for surveillance and treatment in areas with or without available 19S-IgM-FTA-ABS testing.

A risk model for congenital syphilis in infants born to mothers with syphilis treated in gestation: a prospective cohort study.

OBJECTIVE: To explore the risk factors underlying congenital syphilis (CS) and to build a hazards model to assess the risk of CS in offspring born to mothers with syphilis treated in gestation. METHODS: This prospective study observed 554 pregnant women with syphilis and their offspring recruited from August 2002 to May 2007 in Shenzhen Centre for Chronic Disease Control and Prevention. After treatment, all the women were followed up until the diagnosis of CS in their offspring was confirmed or denied. Comparisons were made between women bearing infants with CS and women bearing infants without CS to reveal the risk factors for CS. ORs and their 95% CI were calculated for each risk factor by using logistical regression analysis. RESULTS: Twenty-nine (5.2%) infants were diagnosed with CS. Univariable analyses showed that the reciprocal logarithm of the titre of non-treponemal antibodies in mothers (log (1/T); OR=11.18, p<0.001), gestational week (GW) at treatment (OR=1.10, p<0.001) and the interaction between these two variates (OR=1.09, p<0.001) was associated with CS. Multivariable analysis showed that only the interaction was significantly associated with CS (OR=1.09, p=0.047). CONCLUSIONS: The risk of CS could be predicted by the interaction between GW x log (1/T). Early treatment given to women with syphilis during antenatal care may be the only effective method to decrease the risk of CS.

Congenital syphilis: an economic evaluation of a prevention program in China.

BACKGROUND: Until now there has been no data to show the effectiveness or benefits of screening for syphilis in gravidas in China. This study was to assess the effectiveness of a program preventing mother-to-child-transmission of syphilis and to reveal factors impacting the benefit. METHODS: A cohort of 159,017 gravidas were screened for syphilis by serologic methods and infected individuals were treated with 3 injections of 2.4 million units of benzathine penicillin in Shenzhen in 2005. The pregnancy outcomes were compared for this cost-effectiveness analysis in 2 scenarios, intervention with screening and treatment versus no intervention. RESULTS: Eight hundred twenty-seven pregnant women (0.52%) were diagnosed with syphilis and treated subsequently. Of these, 200 gestations ended in miscarriage. Four babies were diagnosed with congenital syphilis; 25 neonates with low birth weight; 1 died after birth. The total cost was $636,748. On average, every $770 identified 1 infected mother. Every $4391 prevented 1 congenital syphilis; every $5135 prevented 1 low birth weight; and every $7075 prevented 1 death. One disability adjusted life year could be saved by $215. In total the program reached a benefit to cost ratio of 21.76. Sensitivity analyses revealed that this ratio was mainly impacted by the prevalence of syphilis in pregnant women and the rate of miscarriage. CONCLUSIONS: Screening for antenatal syphilis combined with intervening during gestation is highly effective in China. Reducing the percentage of spontaneous/induced abortion would be one of the most effective methods of further increasing the benefits of this screening.

[Study on the status of syphilis infection and its influence factors on pregnant women in Shenzhen].

OBJECTIVE: Through questionnaire and screening, epidemiology of syphilis in pregnant women and related risk factors were studied, to develop effective policy and reducing the negative impact of the disease. METHODS: All pregnant women who appeared at the hospitals the first time, were included, in Shenzhen city. Tolulized Red Unheated Serum Test (TRUST) method was used for primary screening and positive results were confirmed by the Treponema Pallidum Particle Agglutination (TPPA) test at the Shenzhen Center for Disease Control and Prevention (SZCDC). Positive patients were informed and treated and the pregnancies were managed accordingly at the SZCDC. RESULTS: From 2003-2005, 418,871 (94.7%) pregnant were screened. Epidemiological and treatment data were collected from 2019 positive cases of infectious syphilis (0.48%). Among them, 94.2% were between 20 and 35 years old, with 93.6% of them had only junior high school education and 63.4% of them worked as commercial services or jobless which was significantly higher than other occupations (OR = 8.628). 89.5% of them were from other cities, significantly higher than from local residents (OR = 8.733). Gestational weeks at original diagnosis was longer and the infection rate higher. CONCLUSION: The infection rate of syphilis in Shenzhen was still at a high level which was related to occupation, education level, place of residency, gestational weeks at first diagnosis etc. Further screening measures and early intervention were important.

Risk factors for syphilis infection among pregnant women: results of a case-control study in Shenzhen, China.

BACKGROUND: China has been experiencing a rapidly growing syphilis epidemic since the early 1990s, with the reported incidence of congenital syphilis increasing from 0.01 cases per 100,000 live births in 1991 to 19.7 cases per 100,000 live births in 2005. Detailed studies of risk factors for syphilis in pregnant women are needed to inform new preventive interventions. OBJECTIVE: To investigate factors associated with recent syphilis infection among pregnant women and recommend strategies for improved preventive interventions in the community. METHODS: A case-control study was conducted among women attending antenatal clinics in Shenzhen City, South China. Cases were antenatal clinic women testing positive for early syphilis, based on laboratory results, with those testing negative being controls. All participants completed the same anonymous questionnaire covering demographics, lifestyle, sexual behaviour, and sexual partnerships. RESULTS: 129 cases and 345 controls were recruited. Syphilis was significantly associated with unmarried status, less education, multiple sex partners, travel of sex partner in the past 12 months, a history of induced abortion, and previous sexually transmitted infections. Overall, there were no differences between syphilis-positive and negative women in household registration status (hukou), living district and duration in Shenzhen, monthly income, and age at first sex. CONCLUSIONS: Many demographic and behavioural risk factors are associated with syphilis among pregnant women. In the government congenital syphilis control programme, comprehensive preventive interventions should be provided in all clinical settings in addition to the current procedures for syphilis screening among antenatal women.