They said diagnoses of these infections could be important in predicting complications in pregnancy.
Researchers analysed birth records from 354,217 women in Australia who gave birth for the first time between 1999 and 2008.
They then checked the women’s health records and found 3,658 had at least one diagnosed chlamydia infection before the birth, while 196 were had been diagnosed with gonorrhoea. Most of these infections were detected before the conception.
Overall, 4% of women had an unplanned premature birth, 12% had babies who were small for their gestational age, and 0.6% of babies were stillborn.
Researchers accounted for the adverse effects of age, social disadvantage, smoking and conditions such as diabetes and high BP. They found women with prior chlamydia infection were 17% more likely to have an unplanned preterm birth and 40% more likely to have a stillborn baby. However, they were at no greater risk of having a baby that was small for the gestational age.
Women with a prior gonorrhoea infection were twice as likely to have an unplanned preterm birth, but faced no extra risk of having a baby that was small for the gestational age. Too few women had the infection in the study to assess how the infection affected the risk of stillbirth.
Women with chlamydia faced the same risks of unplanned preterm birth whether they were diagnosed a year before conception, within a year of conception, or during pregnancy.
Researchers said the findings did not prove a causal relationship. But they concluded: ‘Our results suggest that sexually transmissible infections in pregnancy and the preconception period may be important in predicting adverse obstetric outcomes.’