Risk Factors for Late-Onset Group B Streptococcal Disease Before and After Implementation of Universal Screening and Intrapartum Antibiotic Prophylaxis.

BACKGROUND: It is unclear whether risk factors for late-onset Group B Streptococcus disease (LOD) have changed since the introduction of universal screening and treatment in 2002.

METHODS: We conducted a case-control study using linked birth certificates and hospital discharge records. All infants born in Washington State from 1992 to 2011 and hospitalized between 7 and 89 days of life with a Group B Streptococcus (GBS)-related International Classification of Diseases (ICD)-9 code were included. Controls were matched 4:1 by birth year. Multivariate logistic regression was used to evaluate the association between clinical characteristics and LOD. We compared differences in the effect of risk factors on LOD between infants born before and after 2002 using likelihood ratio tests.

RESULTS: We identified 138 cases of LOD. In multivariate analyses, prematurity and young maternal age were significantly associated with risk of LOD throughout the study period; positive GBS screen was associated with LOD from 2003 to 2011. Each week of decreasing gestation was associated with a 1.24 (95% confidence interval: 1.15-1.35) times greater likelihood of LOD. We did not detect differences in the association between prematurity or young maternal age and LOD comparing infants born before and after 2002. Compared with infants of non-Hispanic white mothers, risk of LOD among infants of non-Hispanic black mothers decreased after 2002 (adjusted odds ratio [aOR] = 2.74 vs 0.64; pinteraction = 0.02), whereas risk of LOD among infants of Hispanic mothers increased (aOR = 0.80 vs 2.23; pinteraction ≤ 0.001).

CONCLUSIONS: Our results confirm studies conducted before 2002, which found that prematurity and young maternal age were associated with increased risk of LOD. Ethnicity-associated LOD risk differed before and after 2002, which may be related to healthcare access.