**5. Risk factors**

It seems that young women (<25 years old) are more prone to chlamydial infection due to anatomic differences in the cervix, such as cervical ectropion [16, 26]. In this condition, the glandular cells that line the endocervix are present on the ectocervix, leading to exposure of the glandular cells to the vaginal milieu and C. trachomatis has a preference for the glandular epithelium [5, 27].

Other factors associated with an increased risk of infection are numerous sexual partners, sexual intercourse with non-condom use, absence of barrier contraceptives, use of oral contraceptives, partner with concurrent partners or sexually-transmitted disease or non-gonococcal urethritis, non-gonococcal mucopurulent cervititis, sterile pyuria, other sexually transmitted diseases, unmarried status, nulliparity, African/American/Hispanic ethnicity and poor socio-economic condition [5, 23, 28].

Regarding infants, the main risk factor is vertical transmission (mother-tochild) after vaginal birth. Transmission after a cesarean section is unusual, unless premature rupture of the membranes of an infected mother is reported.
