Genital Tract Methicillin-Resistant Staphylococcus aureus: Risk of Vertical Transmission in Pregnant Women

Andrews, William W. PhD, MD; Schelonka, Robert MD; Waites, Ken MD; Stamm, Alan MD; Cliver, Suzanne P.; Moser, Stephen PhD

Obstetrics & Gynecology:
doi: 10.1097/01.AOG.0000298344.04916.11
Original Research

OBJECTIVE: To estimate the frequency of genital tract colonization by methicillin-resistant Staphylococcus aureus (MRSA) among pregnant women and evaluate the association of such colonization with infant outcome.

METHODS: Between July 2003 and July 2006, anovaginal screening cultures for group B Streptococcus (GBS) were prospectively obtained in the third trimester (35 to less than 37 weeks of gestation) and were also processed for identification of Staphylococcus aureus including methicillin-resistant strains. Maternal colonization by MRSA was linked to a computerized database of invasive neonatal infections that occurred at our center during the study period.

RESULTS: Among 5,732 mothers (who delivered 5,804 infants) with GBS screening cultures and infant infection data available, 22.9% were GBS-positive and 14.5% were positive for Staphylococcus aureus. A total of 24.3% of the Staphylococcus aureus isolates were MRSA. The overall MRSA colonization rate was 3.5%. Colonization by any Staphylococcus aureus (relative risk 1.6, 95% confidence interval 1.4–1.9) as well as MRSA (relative risk 2.2, 95% confidence interval 1.6–2.8) was significantly more common among GBS-positive than among GBS-negative women. No cases of early-onset invasive neonatal infection by MRSA occurred among infants in the study.

CONCLUSION: Genital tract colonization with MRSA affected 3.5% of pregnant women. Such MRSA colonization is associated with colonization by GBS but does not predispose to a high risk of early-onset neonatal MRSA infection.


In Brief

Genital tract methicillin-resistant Staphylococcus aureus colonization is common, but it is not associated with a high risk of vertically transmitted, invasive, early-onset neonatal infection.

Author Information

From the Departments of 1Obstetrics and Gynecology, 2Pediatrics, 3Pathology, and 4Internal Medicine, Center for Research in Women's Health, University of Alabama at Birmingham.

Supported in part by a grant from the University of Alabama at Birmingham Health Services Foundation General Endowment Fund.

Corresponding author: William W. Andrews, PhD, MD, Department of Ob/Gyn, University of Alabama at Birmingham, OHB 458, 619 19th Street South, Birmingham, AL 35249-7333; e-mail:

Financial Disclosure The authors have no potential conflicts of interest to disclose.

© 2008 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.