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

Abstract

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.