Introduction: Chlamydia trachomatis causes the most frequent bacterial Sexually Transmitted Infection (STI) in the world. Previous results showed that in Buenos Aires, Argentina, adolescent pregnant women have an unusually high prevalence of this infection. Our aim was to define the frequency of C. trachomatis infection among pregnant women, and to describe its association pattern.

Methods Starting on May 2016, voluntary participation for this study was offered to every pregnant woman attending the Hospital Materno Infantil “Ana Goitia” (Avellaneda, Buenos Aires) during her routine pregnancy control. Those who accepted and signed the Informed Consent form were enrolled. Cervico-vaginal lavage and first catch urine samples were collected. Detection of Chlamydia trachomatis was performed using Real Time PCR. This preliminary report shows the results for the first four months of a two years study, which is still ongoing.

Results One hundred and nineteen pregnant women aged between 14 and 39 years-old were enrolled, with a mean age of 22.85 years-old. Sixty four (53.78%) of them were younger than 22 years-old. C. trachomatis infection was detected on 22 (18.49%) women. The majority of the chlamydia infected patients (76.19%) were 21 years-old or less, which is statistically significant related to the age distribution of the whole analysed group OR: 3,27 (1.11–9.62) p<0.05. Eleven out of 16 C . trachomatis infected patients (68.75%) were associated to lack of inflammatory reaction on vaginal content.

Conclusion The frequency of Chlamydia trachomatis infection on the analysed group was high, and was also significantly associated to the age of the studied women, being higher on women younger than 21 years-old (25%) than on the older ones (9.09%). This evidence supports the need of assessing the addition of the detection of C. trachomatis infection to routine pregnancy control of younger women in Argentina.