Chlamydia trachomatis is an obligate intracellular organism that may be transmitted to neonates from mothers who have cervical infections. This occurs primarily because of delivery through an infected vaginal canal, although documented cases of transmission following c-section are reported. For the neonate, Chlamydia infections are manifested as conjunctivitis, pneumonia, or both. Of neonates who are born to mothers with Chlamydia infections, 25% to 50% will develop conjunctivitis, and 5% to 20% will develop pneumonia. The time of onset for Chlamydia conjunctivitis is 5 to 14 days. The onset of pneumonia is typically 2 weeks to 3 months, with the majority of infants presenting by 2 months. Symptoms may appear earlier, particularly in infants born to mothers with premature rupture of membranes. Of infants who develop Chlamydia pneumonia, 50% had a history of conjunctivitis. Neonates who received prophylaxis with silver nitrate, erythromycin ointment, or tetracycline in the newborn period are still at risk for developing Chlamydia infections because these interventions are ineffective against Chlamydia; neonates receiving these interventions are protected against Neisseria conjunctivitis.

Physical findings of Chlamydia conjunctivitis include a watery discharge that progresses to a purulent discharge with associated eyelid swelling and erythema. The manifestations are generally unilateral but may be bilateral. Untreated Chlamydia infections may result in conjunctiva and corneal scarring over the course of months. The accurate diagnosis of chlamydial conjunctivitis is essential to ensure appropriate management. Because Chlamydia is an intracellular organism, a diagnosis requires obtaining cells by scraping the upper or lower conjunctiva rather than collection of the exudates. Culture is the gold standard for diagnosis, although polymerase chain reaction studies have excellent sensitivities and specificities.