Scientists from the United Kingdom conducted a case-control study to study the epidemiology and determine the risk factors for infection caused by group B streptococcus, both mother and child. The study included children under 90 days of age with an invasive infection caused by group B streptococcus ("case") and healthy children with the same body weight ("controls"). During the study, demographic and medical information was recorded on the state of the mother and the newborn, the course of pregnancy, childbirth and the neon period.

For the period from 2000 to 2003 138 cases of invasive infection caused by group B streptococcus were identified, and information was collected on 305 healthy children (control group). Most cases (74%) of invasive infection caused by group B streptococcus appeared within the first week of life, 89% of them showed clinical signs of infection on the first day of life. In 65% of cases of infection, one or more factors in the process of its development have occurred (premature birth, prolonged anhydrous period, known carrier of group B streptococcus in the mother, fever during childbirth).

As a result of multivariate regression analysis, it was found that birth weight does not affect the risk of developing an infection caused by group B streptococcus. The most important risk factors for developing an infection caused by group B streptococcus were the known carrier of mother group B streptococcus (odds ratio - OS = 6.9), maternal infection during the perinatal period (OS = 4.2) and fever childbirth (OS = 2.2 for each degree of increase in body temperature).

Invasive infection caused by group B streptococcus was associated with a 2-fold increase in the probability of a prolonged anhydrous period and tachycardia in the newborn (p = 0.05 and p = 0.07 , respectively). Children with an early onset of invasive group B streptococcal infection had lower Apgar scores, a higher likelihood of respiratory distress syndrome and seizures, as well as a need for tube feeding, compared to neonates in the control group.

In infants with invasive infection caused by group B streptococcus, longer hospital stays have been observed at all stages of breastfeeding infants. Thus, the infection caused by group B streptococcus considerably increases the costs of the health system for the care of these newborns.