An Observational Cohort Study of Chlamydia trachomatis Treatment in Pregnancy LISA RAHANGDALE, MD,* SARAH GUERRY, MD,† HEIDI M. BAUER, MD, MPH,† LAURA PACKEL, MPH,† MIRIAM RHEW, MD, MPH,‡ ROGER BAXTER, MD,§ JOAN CHOW, MPH, DRPH,† AND GAIL BOLAN, MD† Background and Objectives: Currently, azithromycin is not consid- ered a first-line treatment for Chlamydia trachomatis in pregnant women. We evaluated the use, efficacy, and safety of azithromycin compared with erythromycin and amoxicillin in the treatment of genital chlamydial infection during pregnancy. Methods: This was a retrospective cohort study of pregnant women with genital chlamydial infection. Data on antibiotics prescribed, test- of-cure (TOC) results, and maternal and infant complications were collected from medical records. Results: Of the 277 women in the study sample, 69% were initially prescribed azithromycin, 9% amoxicillin, and 19% erythromycin. Eight-one percent of subjects had a TOC 7 or more days after diag- nosis and before delivery. Treatment efficacy, as defined by a negative TOC, was 97% (95% confidence interval [CI], 92.9 –99.2) for azithro- mycin, 95% (95% CI, 76.2–99.9) for amoxicillin, and 64% (95% CI, 44.1– 81.4) for erythromycin. The efficacy of azithromycin was signif- icantly higher than erythromycin (P <0.0001). There were no signif- icant differences in efficacy by age, race/ethnicity, concurrent sexually transmitted disease diagnosis, partner treatment, or substance use. Furthermore, there was no difference in complications for women or infants exposed to azithromycin compared with those treated with other regimens. Conclusion: Clinical outcome data from this study population of women and infants support both efficacy and safety of azithromycin for treatment of C. trachomatis in pregnancy. EACH YEAR IN THE UNITED STATES, 2.8 million people are infected with chlamydia and more than 155,000 infants are born to chlamydia-infected mothers. 1,2 These newborns are at increased risk of developing eye and lung complications such as conjunctivitis and pneumonia. 3–6 In addition, chlamydial infec- tion has been associated with an increased risk of obstetric complications such as preterm labor and endometritis. 2,7 There- fore, identification and appropriate treatment of infected women are critical during pregnancy. The Centers for Disease Control and Prevention (CDC) cur- rently recommends weeklong courses of erythromycin (500 mg orally 4 times a day for 7 days) or amoxicillin (500 mg orally 3 times a day for 7 days) as first-line therapy for pregnant women. 8 A single dose of 1 g of azithromycin is considered an alternative treatment. 8 Erythromycin can have diminished efficacy secondary to the high frequency of gastrointestinal side effects. 9 –13 There- fore, many physicians prefer treatment with azithromycin. 13–15 Although there have been several studies illustrating the efficacy of azithromycin for the treatment of chlamydia during preg- nancy, 10,12,16 –20 it is not considered a first-line treatment in preg- nant women. Obstetric and neonatal safety data are limited, 17 and there are small numbers of subjects in published studies. This study reviewed physician practice and evaluated efficacy and ma- ternal and infant outcomes associated with different treatment regimens to assess whether the use of azithromycin for treatment of chlamydia during pregnancy as a first-line agent is appropriate. Materials and Methods This was a retrospective cohort study comparing antibiotics used in pregnant women infected with chlamydia at 44 Northern California Kaiser-Permanente clinical facilities. The administra- tive laboratory database was queried for female patients with a positive chlamydia test within 280 days after a positive pregnancy test during the time period of July 1, 1999, to December 31, 2000. Chlamydia testing was performed using cervical swabs analyzed by DNA hybridization probe (PACE2; GenProbe, San Diego, CA). Exclusion criteria included women who had spontaneous abortions (pregnancy loss before 20 weeks), therapeutic abortions, and ec- topic pregnancies. Trained study investigators reviewed patient and infant records using standardized abstraction forms to obtain data on patient demographics, medical history, sexually transmit- ted disease (STD) testing results, medications prescribed, partner management, and maternal and infant complications. To determine whether physician antibiotic-prescribing prac- tices were influenced by patient characteristics, basic demo- graphic information and aspects of patients’ medical histories The authors thank Maggie Chartier, Holly Howard, and MiSuk Kang for assistance with medical record abstraction; Denise Gilson for data entry; Rene Gindi and Deborah Johnston for preliminary data analysis; Michael Samuel for assistance with statistical analysis; and Deborah Cohan and Jody Steinauer for critical review of the manuscript. This project was supported in part by the Centers for Disease Control and Prevention (Comprehensive STD Prevention Systems and Infertility Prevention Project grant no. H25/CCH904362) and the California Depart- ment of Health Services. Correspondence: Lisa Rahangdale, MD, Department of Obstetrics, Gy- necology & Reproductive Sciences, University of California, San Fran- cisco, 1001 Potrero Ave., Ward 6D-8, San Francisco, CA 94110. E-mail: RahangdaleL@obgyn.ucsf.edu. Received for publication May 5, 2005, and accepted July 17, 2005. From the *Department of Obstetrics, Gynecology, & Reproductive Sciences, University of California, San Francisco, California; the †California Department of Health Services Sexually Transmitted Disease Control Branch; the ‡Preventive Medicine Residency, University of California, San Francisco, California; and the §Department of Infectious Diseases, Kaiser-Permanente, Oakland, California Sexually Transmitted Diseases, February 2006, Vol. 33, No. 2, p.106 –110 DOI: 10.1097/01.olq.0000187226.32145.ea Copyright © 2006, American Sexually Transmitted Diseases Association All rights reserved. 106