Objective: To estimate the prevalence of group B streptococci (GBS) colonization in a subsequent pregnancy in women with and without GBS colonization in an index pregnancy.
Methods: A retrospective cohort study of women who had two consecutive deliveries with the availability of GBS culture result at 35 to 37 weeks of gestation or the diagnosis of GBS colonization by urine culture for both pregnancies was undertaken. Women in the index pregnancy with GBS genitourinary tract colonization were compared by culture date with the next woman that screened negative for GBS colonization. To detect a doubling of GBS colonization from 20% to 40% would require 91 women in each arm at P<.05 with a power of 80%. Risk factors for GBS colonization were ascertained. Univariable and conditional logistic regression analyses were performed. P<.05 was considered statistically significant.
Results: A total of 102 women positive for GBS genitourinary colonization were compared with controls. The rate of recurrence for GBS colonization (53%) was significantly higher when judged against women GBS negative in their index pregnancy (15%) (adjusted odds ratio 11.7, 95% confidence interval 3.5-38.9, P<.01). Women who were GBS positive in the index pregnancy were more often of African-American race and less likely to be nulliparous or smoke tobacco.
Conclusion: Women with GBS colonization are at increased risk of GBS colonization in a subsequent pregnancy. Prior GBS colonization should be considered in the algorithm to treat unknown GBS status during term labor.