Rui Gao, MD, PhD; Buyun Liu, MD, PhD; Wenhan Yang, MD, PhD; Yuxiao Wu, MS; Bo Wang, MD, PhD; Mark K. Santillan, MD, PhD; Kelli Ryckman, PhD; Donna A. Santillan, PhD; Wei Bao, MD, PhD

IMPORTANCE Maternal infection has been implicated in the pathogenesis of preterm birth through intrauterine inflammatory response. Chlamydia, gonorrhea, and syphilis are among the most common sexually transmitted infections worldwide, but studies on their association with preterm birth are sparse.

OBJECTIVE To examine the association between maternal chlamydia, gonorrhea, and syphilis infections in pregnancy and the risk of preterm birth in a large population-based study in the US.

DESIGN, SETTING, AND PARTICIPANTS This population-based retrospective cohort study examined nationwide birth certificate data from the US National Vital Statistics System between 2016 and 2019. All mothers who had a singleton live birth and available data on chlamydia, gonorrhea, or syphilis infection before or during pregnancy and gestational age at birth were included in analysis

EXPOSURES Sexually transmitted infection (chlamydia, gonorrhea, or syphilis) occurring before or during pregnancy.

MAIN OUTCOMES AND MEASURES Preterm birth, defined as gestational age less than 37 weeks.

RESULTS This study included 14 373 023 mothers (mean [SD] age 29 [5.8] years; Hispanic, 3 435 333 [23.9%]; non-Hispanic Asian, 912 425 [6.3%]; non-Hispanic Black, 2 058 006 [14.3%]; and non-Hispanic White, 7 386 568 [51.4%]). Among the mothers, 267 260 (1.9%) had chlamydia, 43 147 (0.3%) had gonorrhea, and 16 321 (0.1%) had syphilis. Among the newborns, 1 146 800 (8.0%) were preterm births. The rate of preterm birth was 9.9%, 12.2%, and 13.3% among women with chlamydia, gonorrhea, and syphilis infection, respectively. After adjustment for sociodemographic and medical and/or health factors, the adjusted odds ratio of preterm birth was 1.03 (95% CI, 1.02-1.04) for chlamydia, 1.11 (95% CI, 1.08-1.15) for gonorrhea, 1.17 (95% CI, 1.11-1.22) for syphilis, and 1.06 (95% CI, 1.05-1.07) for any of these sexually transmitted infections comparing mothers with these conditions and those without.

CONCLUSIONS AND RELEVANCE Maternal sexually transmitted infections (gonorrhea, syphilis, or chlamydia) were associated with an increased risk of preterm birth. Pregnant women with sexually transmitted infections before or during pregnancy might benefit from targeted prevention for preterm birth.

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