Group B Streptococcus colonization at delivery is associated with maternal peripartum infection.

Background: Group B Streptococcus (GBS) is a major cause of serious neonatal infection but its role in maternal morbidity has received little investigation. The aim of this study was to determine whether GBS colonization at delivery is associated with increased risk of maternal peripartum infection.

Methods: In this prospective cohort study, 1746 unselected women had a vaginal-rectal culture taken at the onset of labor. Diagnosis of maternal peripartum infection was based on a combination of two or more signs or symptoms including fever, breast pain, severe wound or pelvic pain, purulent discharge and abnormal laboratory tests including C-reactive protein and white blood cell count occurring from labor until 2 weeks postpartum. The main outcome measure was the proportion of women with maternal peripartum infection according to GBS colonization status.

Results: A total of 25.9% (452/1746) women were colonized with GBS. The rate of peripartum infection was almost twice as high in colonized women (49/452 [10.8%]) vs. non-colonized women (81/1294 [6.3%]); OR 1.82 [1.26-2.64], p = 0.002). This association was confirmed in a multivariable model (OR 1.99 [1.35-2.95], p = 0.001). Women diagnosed with peripartum infection had a significantly longer hospital stay compared to women without peripartum infection (4 days (median) vs. 3 days, p < 0.001). Length of hospital stay did not differ between colonized and non-colonized women. Serotype IV GBS was more frequent in colonized women with peripartum infection than in women without peripartum infection (29.3% vs. 12.5%, p = 0.003).

Conclusions: GBS colonization at delivery is associated with increased risk of peripartum infection. Whether this increase is due directly to invasion by GBS or whether GBS colonization is associated with a more general vulnerability to infection remains to be determined.