Preconception reproductive tract infections status and adverse pregnancy outcomes: a population-based retrospective cohort study

BACKGROUND: Reproductive tract infections can cause serious adverse outcomes for pregnant women such as spontaneous abortion and preterm birth. However, it is unclear whether maternal reproductive tract infection before pregnancy would also be related to any adverse pregnancy outcomes. This study aims to investigate the association of maternal preconception reproductive tract infections with subsequent adverse pregnancy outcomes. METHODS: A retrospective cohort study was conducted in the Chongqing Municipality of China between April 2010 and December 2016. A total of 57,586 women (57,708 pregnancies) from all 39 counties of Chongqing who participated in the National Free Preconception Health Examination Project were included. They all took preconception examinations for gonorrhea, chlamydia, trichomoniasis, syphilis, bacterial vaginosis and candidiasis before pregnancy within one year. Primary outcomes included spontaneous abortion (< 28 weeks gestation), preterm birth (< 37 weeks gestation), macrosomia and low birthweight. RESULTS: Of the 57,708 pregnancies, 2438 (4.22%) had at least one type of reproductive tract infections. Compared with women who were not infected with any reproductive tract infection before pregnancy, women with reproductive tract infections had a higher rate of spontaneous abortion (7.88% vs. 5.62%, p < 0.001). After analyzing by each infection, there were few significant associations between pre-pregnancy infections and adverse outcomes. Preconception syphilis infection was significantly associated with increased odds of spontaneous abortion (aOR = 2.07, 95%CI 1.50–2.85), induced abortion/labour due to medical reasons (aOR = 1.60, 95%CI 1.01–2.54) and preterm birth (aOR = 1.60, 95%CI 1.12–2.30) after adjusting for potential confounders. Preconception trichomoniasis was intended to relate to a higher risk of spontaneous abortion (aOR = 1.65, 95%CI 1.01–2.71), but its impact seemed to be attributed to its co-infection with other RTIs. Women who were chlamydia or bacterial vaginosis positive before pregnancy showed higher odds of macrosomia (aOR = 2.00, 95% CI 1.07–3.74 for chlamydia; aOR = 1.58, 95% CI 1.06–2.34 for bacterial vaginosis). Preconception bacterial vaginosis might also be associated with higher risks of very preterm birth (aOR = 2.16, 95%CI 1.23–3.78) and large for gestational age (aOR = 1.36, 95%CI 1.02–1.81). CONCLUSIONS: Women with infections of the genital tract before pregnancy might also have increased risks of subsequent adverse outcomes including spontaneous abortion, preterm birth and macrosomia. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12884-022-04836-3.