The use of antibiotics during pregnancy to prevent infection of the newborn with group B β-hemolytic streptococcus reduces the frequency of infections in newborns caused by this pathogen. However, the relationship between the intrauterine effect of antibiotics on the fetus and the frequency of severe bacterial infections of different etiology in newborns has remained unexplored until recently.

American scientists conducted a case-control study to assess the relationship between the risk of developing serious bacterial infections in term infants aged 7 to 90 days and intrauterine exposure to antibiotics. The study included 90 infants with serious infections that developed between 7 and 90 days and 92 healthy children who were the control group.

Infants who developed the infection were more likely to have intrauterine exposure to antibiotics than healthy children (41% vs 27%) (standardized odds ratio [SOS ] 1.96; 95% confidence interval [CI] 1.05-3.66). This relationship was more pronounced if the pregnant woman received a broad-spectrum antibiotic (SOS 4.95; 95% CI 2.04-11.98). Infectious agents had a higher level of resistance to ampicillin (grade 5.7; 95% CI 2.3-14.3) in children whose mothers took antibiotics during pregnancy. Intrauterine exposure to antibiotics increased the risk of urinary tract infections, meningitis, omphalitis, and bacteremia caused by ampicillin-resistant pathogens.

Thus, infants with severe bacterial infections that developed from the 7th to 90th day of life were more likely to be exposed to antibiotics in utero than healthy children, and the agents responsible for these infections are characterized by a higher level of resistance to ampicillin.