Predictors of Staphylococcus aureus Rectovaginal Colonization in Pregnant Women and Risk for Maternal and Neonatal Infections.

Background: Staphylococcus aureus infections are increasing among pregnant and postpartum women and neonates, but risk factors for S. aureus colonization in pregnancy and the association between maternal colonization and infant infections are not well defined. We sought to identify risk factors for maternal S. aureus rectovaginal colonization and assess colonization as a risk factor for infections among mothers and infants.

Methods: We conducted a retrospective cohort study of pregnant women and their infants. Demographic and clinical data, including S. aureus infections that occurred in mothers from 3 months before to 3 months after delivery and in infants during the first 3 months of life, were extracted from electronic medical records. Predictors for maternal S. aureus rectovaginal colonization were assessed through multivariable logistic regression analysis.

Results: The cohort included 2702 women and 2789 infants. The prevalence of maternal rectovaginal colonization with methicillin-susceptible S. aureus and methicillin-resistant S. aureus (MRSA) was 13% and 0.7%. Independent predictors of colonization included multigravidity, human immunodeficiency virus seropositivity, and group B Streptococcus colonization. S. aureus colonization was associated with an increased risk of infection in mothers (odds ratio [OR], 3.5; 95% confidence interval [CI], 1.4-8.8) but not in their infants (OR, 1.9; 95% CI, .6-5.6). The frequency of S. aureus infections was 0.8% in mothers and 0.7% in infants.

Conclusions: S. aureus rectovaginal colonization was associated with an increased risk of infections in women but not in their infants. The frequency of MRSA infections was low. These data suggest that routine MRSA screening of pregnant women may not be indicated.