Background Chlamydia trachomatis (CT) is the commonest STI in the UK with high prevalence in pregnancy. CT testing is not routinely recommended for pregnant women in the UK despite adverse effects on pregnancy, neonate and mother. Countries with recommended CT screening in pregnancy have good results despite suboptimal uptake.

Aim(s) To determine the prevalence of CT and treatment uptake in pregnant and non-pregnant women who have attended a large, busy urban integrated sexual health service.

Methods Retrospective observational cohort study of all patient encounters with women of child bearing age (15 to 49) between 2012 and 2015 who were tested for CT. Women with a positive pregnancy and STI testing 2 weeks prior and 9 months post STI test were included (n = 837). Women with terminations were excluded. Socio-demographic factors and clinical factors were compared to 20,629 women who had a CT test but no pregnancy.

ResultsPregnant women were on average younger (25 vs 28) and had higher CT prevalence across all age groups (12 vs 5%), peaking between 15 and 25 years (21 vs 10%). Being pregnant doubled the odds of having CT after controlling for age (adjusted OR 1.96; CI 1.64–2.30).

Discussion The national opportunistic screening programme is deemed to cover CT detection in an age group where both STIs and pregnancy rates are high. However, the results of our study support additional targeted CT screening during pregnancy, particularly in the youngest age group.