Global & Regional Estimates of Preterm and/or Low Birthweight Infants attributable to Gestational Syphilis, 2015 & 2020

Abstract

Introduction: Premature birth and low birthweight are adverse outcomes of gestational syphilis. Preterm or low birthweight infants often experience health issues such as respiratory infections, diarrheal diseases, encephalopathy due to birth asphyxia, hemolytic disease, and other neonatal disorders. In addition to these immediate human consequences, their management also translates to financial distress on both the family and healthcare system. It is necessary for estimates of preterm and low birthweight infants to be included in conversations about the burden of syphilis during pregnancy. This analysis focuses on estimating the number of preterm and/or low birthweight infants attributable to gestational syphilis on a global and regional level. It also compares estimates generated within this study to those estimated in a previous study. Methods: Data from a systematic review including studies on preterm/low birthweight infants exposed to gestational syphilis were reviewed for inclusion. Measurements of the rate of preterm/low birthweight among women with syphilis during pregnancy and among women without syphilis during pregnancy were extracted. An excess rate and relative risk approach were used to estimate the outcome. Meta-analyses were conducted with covariates on maternal treatment status. Results of the excess rate and relative risk meta-analyses were applied separately to estimate the number of preterm/low birthweight infants attributable to syphilis during pregnancy by each approach. Results: The excess rate approach estimated 503,799 preterm/low birthweight infants attributable to syphilis globally in 2020. The relative risk approach estimated 116,124 preterm/low birthweight infants attributable to syphilis globally in 2020. For both approaches, estimates of the outcome were highest in the African region and lowest in the European & Eastern Mediterranean regions. Comparing the results of this analysis and previous estimates of preterm/low birthweight attributable to syphilis, estimates from each approach used in this analysis exceed previous estimates of the outcome on a global and regional level. Discussion: Considering the excess rate and relative risk approaches, the relative risk approach is the more rigorous, and thus preferred estimation methodology, as it requires an additional indicator to estimate the outcome. Further investigation is needed to assess other aspects of each methodology that contribute to differences in final values. Between the excess rate approach used for this study and the excess rate approach used in a previous study, differences in the treatment-specific excess rate values utilized for each lend themselves to differences in final values. Disparity in the excess rate values between untreated women are due to a disparate number of data sources between each study, and between partially or fully treated women, variation in the analysis techniques. Alignment of data sources and innovation in data processing are a vital starting point for aligning estimates at a regional and global level across research groups. Comprehensive treatment of pregnant women with syphilis is beneficial for the reduction of preterm and/or low birthweight infants, and must be preceded by early screening of syphilis during antenatal visits.