What are the risks of early and late onset Group B Streptococcus (GBS) disease in a 6-day-old newborn born at 37 weeks gestation to a mother with a history of GBS positivity in a previous pregnancy, without GBS testing or antibiotic prophylaxis during labor?

Risk Assessment for GBS Disease in a 6-Day-Old Infant

At 6 days of age with no signs of sepsis and no fever in mother or baby, the risk of early-onset GBS disease has essentially passed, but this infant remains at ongoing risk for late-onset GBS disease through 3 months of age, particularly given the maternal history of GBS colonization in a previous pregnancy and lack of intrapartum antibiotic prophylaxis.

Early-Onset GBS Disease Risk (Now Minimal)

The window for early-onset GBS disease has effectively closed. Early-onset GBS disease is defined as isolation of GBS from a normally sterile site within the first 6 days of life, though it typically presents within 12-24 hours after delivery 1. At day 6 of life with no clinical signs, this infant has passed through the highest-risk period.

Why This Infant Was at Elevated Risk Initially

This infant had multiple risk factors that should have triggered intrapartum antibiotic prophylaxis:

• Unknown GBS status at delivery - The mother was not screened at 35-37 weeks gestation (current pregnancy), which is the recommended screening window 1, 2
• History of GBS positivity in previous pregnancy - While this alone doesn't mandate prophylaxis (as GBS colonization can be transient between pregnancies), it increased suspicion 1
• Prolonged rupture of membranes - 20-30 minutes does NOT meet the ≥18 hours threshold that would have mandated empiric prophylaxis for unknown GBS status 2, 3
• No intrapartum fever - Temperature remained <100.4°F, so this risk factor was absent 2, 3
• Term delivery at 37 weeks - This is not a risk factor; prophylaxis for unknown GBS status is only indicated if delivery occurs <37 weeks 2, 3

The mother should have received intrapartum antibiotic prophylaxis IF she had tested positive for GBS in this pregnancy, but since she was not tested and had no intrapartum risk factors (fever, prolonged rupture ≥18 hours, or preterm delivery), prophylaxis was not indicated by current guidelines 2, 3.

Current Early-Onset Risk Assessment

The infant is now well-appearing at 6 days with no fever and no signs of sepsis. Signs of early-onset GBS disease include tachycardia, tachypnea, lethargy, and can progress to severe cardiorespiratory failure 1. Since none of these signs are present at day 6, early-onset disease is highly unlikely.

Late-Onset GBS Disease Risk (Ongoing Through 3 Months)

This infant remains at risk for late-onset GBS disease, which is defined as identification of GBS from a normally sterile site from 1 week to less than 3 months of age 1.

Key Differences from Early-Onset Disease

• Maternal colonization at birth is less responsible for late-onset disease - The average incidence of late-onset GBS did not change from 2006 to 2015 despite widespread implementation of intrapartum antibiotic prophylaxis 1
• Acquisition from non-maternal caregivers may contribute to late-onset disease 1
• Higher rate of meningitis - Meningitis occurs in 31% of late-onset cases compared to only 10% of early-onset cases 1
• Bacteremia is common - Found in 93% of infants with late-onset GBS disease 1

Risk Factors Present in This Case

• Positive maternal GBS screening in a previous pregnancy - This is strongly associated with late-onset GBS disease 1
• Term birth - While preterm birth increases risk, term infants still develop late-onset disease 1

Clinical Presentation to Monitor For

Parents and providers should watch for signs of late-onset GBS disease through 3 months of age 1:

• Fever ≥100.4°F - Most common presenting sign 1
• Lethargy or poor feeding 1
• Irritability 1
• Respiratory symptoms - Tachypnea, grunting, or apnea 1
• Signs of meningitis - Irritability, vomiting, temperature instability, bulging fontanelle, or seizures 1

If Late-Onset Disease is Suspected

Evaluation should include 1:

• Blood culture
• Urine culture
• Cerebrospinal fluid culture and analysis
• Inflammatory markers

Empiric treatment with ampicillin plus an aminoglycoside is recommended for infants up to 7 days of age, with broader coverage if needed for infants 8-28 days of age 1.

Critical Pitfall to Avoid

Do not assume that the absence of symptoms at 6 days means this infant is "out of the woods" for GBS disease. The risk profile has shifted from early-onset to late-onset disease, and vigilance must continue through 3 months of age 1. Parents should be counseled to seek immediate medical attention for any fever or signs of illness during this period.