Abstract

Objectives: To determine the risk factors associated with chlamydial infection in pregnancy and the sensitivity and specificity of these when used for selective screening.

Methods: A prospective, cross-sectional study of pregnant women aged 16-25 years attending four major public antenatal services across Melbourne, Australia. Between October 2006 and July 2007, women were approached consecutively and asked to complete a questionnaire and to provide a first-pass urine specimen for Chlamydia trachomatis testing using polymerase chain reaction.

Results: Of 1180 eligible women, 1087 were approached and 1044 (88%) consented to participate. Among the 987 women for whom a questionnaire and a definitive diagnostic assay were available, the prevalence of chlamydia was 3.2% (95% CI: 1.8-5.9). In a multiple logistic regression model, younger age (≤20 years) (adjusted odds ratio (AOR): 2.1 (95% CI: 0.6, 7.9)) and reporting more than one sex partner in the prior 12 months (AOR: 11.5 (95% CI: 7.1, 18.5)) were each associated with chlamydia infection. The use of any antibiotic within 3 months (AOR: 0.2 (95% CI: 0.1, 0.6)) was associated with reduced odds for infection. Screening restricted to women who reported more than one sex partner in the prior 12 months would have detected 44% of infections in women aged 16-25 years, with only 7% of women being screened. The addition of women aged 20 and under would have detected 72% of infections, requiring 27% of women to be screened.

Conclusions: Selective chlamydia screening of pregnant women based on risk factors can improve the yield from screening. However, the potential harm of missed infections among excluded women would need to be considered.