Risk Factors for Chlamydia trachomatis Infection and Preterm Birth in Pregnant Japanese Women: Does Chlamydial Infection Cause Preterm Birth?

The aim of this study was to clarify the risk factors for chlamydial infection and determine whether infection during pregnancy is associated with preterm birth in Japanese women. The subjects were women who underwent Chlamydia trachomatis polymerase chain reaction testing during a singleton pregnancy and delivered after the 22nd week of gestation at a tertiary care center between January 1, 2000 and December 31, 2016. We compared Chlamydia-positive (n = 259) and Chlamydianegative (n = 1,974) groups and evaluated the pregnancy outcomes. The Chlamydia-positive group had a higher rate of public assistance coverage, smoking during pregnancy, nulliparity, lack of a partner, presence of other sexually transmitted infections, high-risk social status, and younger age (P < 0.01). The incidence of preterm births was not different between the groups, with an odds ratio of 0.95 (95% confidence interval: 0.62-1.46). The incidences of low birth weight deliveries, premature rupture of membranes, and preterm premature rupture of membranes prior to the 37th week were also comparable between the groups. Chlamydial infection during pregnancy had no effect on preterm birth, even after adjustment for confounding factors.