BACKGROUND: Chlamydia trachomatis is a common sexually transmitted bacteria pathogen which might be implicated in miscarriage. OBJECTIVES: To evaluate the frequency of chlamydia trachomatis antibodies among women who experienced spontaneous miscarriage and compare it with those women without miscarriage. DESIGN: A comparative cross sectional study comparing 130 cases of women with spontaneous abortion to the control group which comprised of pregnant women without miscarriage that were matched for age, parity and gestational age. SETTING: This study was conducted in the Obstetrics and Gynecology Department of Lagos University Teaching Hospital. METHODS: Patients with spontaneous abortions were studied and antenatal patients in the first and second trimester of normal pregnancy served as the comparative group. Information on the socio demographic factors was obtained using a proforma. Serum was collected from each participant to detect IgG specific Chlamydia antibodies.