Development and validation of an individualised nomogram to predict mother-to-child transmission in pregnant women with syphilis in China: a retrospective cohort study.

OBJECTIVES:The elimination of mother-to-child transmission (MTCT) of syphilis has been set as a public health priority. However, an instrument to predict the MTCT of syphilis is not available. We aimed to develop and validate an intuitive nomogram to predict the individualised risk of MTCT in pregnant women with syphilis in China. DESIGN:Retrospective cohort study. SETTING:Data was acquired from the National Information System of Prevention of MTCT of Syphilis in Guangdong province between 2011 and 2020. PARTICIPANTS:A total of 13 860 pregnant women with syphilis and their infants were included and randomised 7:3 into the derivation cohort (n=9702) and validation cohort (n=4158). PRIMARY OUTCOME MEASURES:Congenital syphilis. RESULTS:Among 13 860 pregnant women with syphilis and their infants included, 1370 infants were diagnosed with congenital syphilis. Least absolute shrinkage and selection operator regression and multivariable logistic regression showed that age, ethnicity, registered residence, marital status, number of pregnancies, transmission route, the timing of syphilis diagnosis, stage of syphilis, time from first antenatal care to syphilis diagnosis and toluidine red unheated serum test titre were predictors of MTCT of syphilis. A nomogram was developed based on the predictors, which demonstrated good calibration and discrimination with an area under the curve of the receiver operating characteristic of 0.741 (95% CI: 0.728 to 0.755) and 0.731 (95% CI: 0.710 to 0.752) for the derivation and validation cohorts, respectively. The net benefit of the predictive models was positive, demonstrating a significant potential for clinical decision-making. We have also developed a web calculator based on this prediction model. CONCLUSIONS:Our nomogram exhibited good performance in predicting individualised risk for MTCT of syphilis, which may help guide early and personalised prevention for MTCT of syphilis.