Infection with chlamydia or gonorrhea before or during pregnancy was associated with an risk of birth complications, researchers reported.
In a retrospective cohort study, chlamydia infection diagnosed before or during a first pregnancy was linked with an increased risk of spontaneous preterm birth (OR 1.17, 95% CI 1.01-1.37) and stillbirth (OR 1.40, 95% CI 1.00-1.96), according to Bette Liu, MBBS, DPhil, of the University of New South Wales in Sydney, Australia, and colleagues.
Gonorrhea was associated with preterm birth but not stillbirth, and neither infection was linked to having babies small for their gestational age, Liu and colleagues reported online in Sexually Transmitted Infections.
Diagnoses of sexually transmitted lower genital tract infections -- and especially chlamydia -- have been rising among young adults, the researchers noted. Evidence is mixed on whether infections such as chlamydia and gonorrhea diagnosed during pregnancy predispose women to adverse obstetric outcomes. And there is little evidence on the effect of infections diagnosed before conception, Liu and colleagues added.
To help fill the gap, they turned to two databases in New South Wales, the most heavily populated state in Australia, to understand the link between chlamydia and gonorrhea and three adverse outcomes -- preterm birth, stillbirth, and an infant small for gestational age.
The state's Notifiable Conditions Information Management System contained data on sexually transmitted diseases, while the Perinatal Data Collection yielded information on births. De-identified records for both were available from 1999 through 2008.
During those 10 years, analysis showed, 354,217 women had a singleton first birth, including 3,658 (or 1.0%) with at least one chlamydia diagnosis before the birth and 196 (or 0.06%) who had at least one gonorrhea diagnosis.
Most of the diagnoses occurred before the estimated time of conception -- 81.3% for chlamydia and 84.7% for gonorrhea, Liu and colleagues reported. Half of those diagnosed with gonorrhea had also been infected with chlamydia.
Overall, the investigators found, 4% of the women had an unplanned premature birth, 12% had babies small for their gestational age, and 0.6% of the babies were stillborn.
In an analysis adjusted for range of confounding factors, including ages, socioeconomic status, and ethnicity, Liu and colleagues found that in addition to the increased odds of complications for patients with chlamydia, those with a prior diagnosis of gonorrhea had an odds ratio for preterm birth of 2.50 (95% CI 1.39-4.50).
Because of the small number of cases, the researchers could not investigate the impact of the timing of gonorrhea infection on adverse obstetric outcomes. But Liu and colleagues reported that the timing of a chlamydia infection had little effect on the risk of an unplanned premature birth.
Liu and colleagues cautioned that the findings give no insight into cause and effect. In particular, it is possible that chlamydia and gonorrhea are "markers of a higher-risk obstetric population" with unmeasured causal factors that explain the associations.
But, they concluded, the findings suggest that "sexually transmissible infections in pregnancy and the preconception period may be important in predicting adverse obstetric outcomes."
Primary source: Sexually Transmitted Infections
Source reference: Liu B, at al "Chlamydia and gonorrhoea infections and the risk of adverse obstetric outcomes: a retrospective cohort study" Sex Transm Infect 2013; DOI: 10.1136/sextrans-2013-051118.