The co-infection of sexually transmitted infections (STIs) is harmful to pregnant women who live with HIV, as well as the children they are expecting. Particularly, STIs such as human immunodeficiency virus (HIV) , syphilis  and hepatitis B virus (HBV) could be passed from mother to children during gestation period , the adverse pregnancy outcomes of which include miscarriage, stillbirth, preterm delivery and neonatal death. Mother-to-child transmission (MTCT) of STIs are preventable with early intervening approaches. However, without any interventions from gestation, infants who infected congenitally will grow up with pathogens, especially HBV and HIV , and transmit those to others at some stage of their lives. Infection of HIV and syphilis in infants often occur simultaneously due to the similar pathways of transmission (i.e., from the placenta) . Maternal co-infection with HIV and syphilis is dangerous. The secondary infection speeds up the progression of HIV-related conditions. The treatment outcomes of HIV-positive pregnant women are usually not ideal either . The co-infection of HIV and syphilis may compromise the placental barrier and increase the vulnerability of the fetus to both infections . Besides, there is a higher risk of developing early neurological and ophthalmic defects among infants .
STIs are hyperendemic and the co-infection of which remains a significant public health concern in many developing countries. The global incidence of STIs is estimated at over 125 million cases yearly . In Asia, syphilis prevalence was around 2.5% among people living with HIV, for instance, 1.6% among HIV infected women in India . HIV-syphilis co-infection is very prevalent in the developing countries that are suffering from poverty and under-serviced health care because fewer resources and fundings are pointed to healthcare systems in these places . Sub-Saharan countries such as Rwanda, Tanzania, Ethiopia, Uganda, Zambia, and Nigeria are coming across a greater problem of maternal HIV-syphilis co-infection than any other part of the world . In Congo, it was reported that the HIV-syphilis co-infection occurred at the rate of 0.73% among pregnant women attending antenatal clinics. The syphilis-infection in HIV-positive pregnant women increased from 6.0–10.8% from 2002 to 2011 in Rwanda . Another few cross-sectional studies in Tanzania indicated a co-infection rate was found at around 0.7–1.4% in pregnant women . Whereas, it is not a concern in developed countries like the United States - the prevalence of syphilis in women is close to 0.023%, and the co-infection with HIV is already not concentrated in pregnant women .
In China, the STIs have also been spreading widely since the last century . Given the large population base, China is facing severe challenges of MTCT caused by HIV and syphilis infection . Several previous studies reported the prevalence of HIV or syphilis infection in Chinese pregnant women at 0.05–0.10% (2009 to 2013) . In order to curb the epidemics in pregnant women, and to fulfill the international obligation on the elimination of MTCT of HIV and syphilis, from 2001, National Center for women and children’s health Chinese Center for Disease Control and Prevention (China CDC) established a series of pilot study sites in health facilities in the high-risk region to explore the optimal intervention strategies. Followed by that, In 2004, the Central Government started to provide financial support to programsites . In 2010, the National Implementation Guidelines on Integrated Prevention of Mother-to-Child Transmission (iPMTCT) of HIV, syphilis, and HBV program initiated to provide comprehensive service to pregnant women . Starting from 2015, China government invested 1.4 billion RMB (approximately 206 million USD) in the iPMTCT programon an annyal basis, which increased the expansion of coverage nationally. The local clinics offer all pregnant women with free screening, counseling, and testing of HIV, syphilis, and HBV during regular obstetric inspections to pregnant women and follow-up treatment to their exposed children. China is one of the pioneering countries in the world developed the iPMTCT strategies for HIV, syphilis, and HBV. Based on the National iPMTCT Programme, with national effort experts and the support from the elimination of mother-to-child transmission (EMTCT) programled by the United Nation, we expect to see the EMTCT goal of “getting to zero” are largely achieved in the next decade .
We believed, a few years after the iPMTCT programimplementation, it is essential to profile the overall trend of HIV-syphilis co-infection in pregnant women to summarize the phase progression of the early intervention. By identifying the risk factor for co-infection, we may further tailor the program to match the need of pregnant women at different disease stages or from different socioeconomic backgrounds. In this study, we reported the prevalence and trends of maternal HIV-syphilis co-infection among HIV-infected pregnant women in China, as well as socioeconomic factors associated with HIV-syphilis co-infection. We then further explored the risk factors leading to infant death. This work will direct the obstetrics clinical practitioners and STI program managers to adapt the strategies to deliver the care services to pregnant women better.