How should a newborn be managed when the mother is Group B Streptococcus‑positive, including whether to give empiric antibiotics based on intrapartum antibiotic timing and maternal penicillin allergy?

Management of Newborns Born to GBS-Positive Mothers

The management of newborns born to GBS-positive mothers depends primarily on whether the infant shows signs of sepsis, whether maternal chorioamnionitis was present, and whether the mother received adequate intrapartum antibiotic prophylaxis (≥4 hours of penicillin, ampicillin, or cefazolin before delivery). 1

Immediate Full Evaluation and Treatment Required

Any newborn with clinical signs of sepsis requires immediate full diagnostic evaluation and empiric antibiotic therapy, regardless of maternal GBS status or adequacy of intrapartum prophylaxis. 1, 2

• Full diagnostic evaluation includes blood culture, complete blood count with differential and platelets, chest radiograph if respiratory abnormalities present, and lumbar puncture if the patient is stable enough to tolerate the procedure 1
• Empiric therapy should include ampicillin for GBS coverage plus gentamicin for gram-negative coverage, accounting for local resistance patterns 1
• Clinical signs warranting this approach include respiratory distress, temperature instability, hemodynamic instability, or altered consciousness 3

Maternal Chorioamnionitis Present

If the mother received intrapartum antibiotics for suspected chorioamnionitis, the newborn requires limited evaluation and empiric antibiotic therapy pending culture results, regardless of clinical condition at birth, duration of maternal antibiotics, or gestational age. 1

• Limited evaluation includes blood culture at birth and CBC with differential and platelets at birth and/or at 6-12 hours of life 1
• Empiric therapy should be ampicillin and gentamicin 1, 2

Well-Appearing Infant, No Chorioamnionitis, Adequate IAP

For well-appearing infants born at ≥37 weeks gestation whose mothers received adequate intrapartum antibiotic prophylaxis (≥4 hours of penicillin, ampicillin, or cefazolin) and had membrane rupture <18 hours, observation for ≥48 hours is sufficient. 1, 2

• Adequate prophylaxis is defined as ≥4 hours of IV penicillin, ampicillin, or cefazolin before delivery 1, 2
• Beta-lactam prophylaxis given ≥4 hours before delivery is 91% effective in preventing early-onset GBS disease in term infants and 86% effective in preterm infants 4
• Observation may occur at home after 24 hours if the infant is >38 weeks gestation, other discharge criteria are met, access to medical care is readily available, and a responsible person capable of monitoring and transporting the infant is present 1
• If these conditions are not met, the infant should remain hospitalized for at least 48 hours 1

Well-Appearing Infant, No Chorioamnionitis, Inadequate or No IAP

For well-appearing infants born at ≥37 weeks with membrane rupture <18 hours whose mothers received <4 hours of IAP, observation for ≥48 hours is recommended. 1

For well-appearing infants born at <37 weeks OR with membrane rupture ≥18 hours, limited evaluation plus observation for ≥48 hours is required. 1

• Limited evaluation includes blood culture at birth and CBC with differential and platelets at birth and/or at 6-12 hours of life 1
• These infants require hospital observation for at least 48 hours 1

Critical Considerations Regarding IAP Duration

Recent evidence suggests that even "inadequate" IAP with beta-lactams (less than 4 hours) provides substantial protection, though not as robust as ≥4 hours. 5

• Prophylaxis of 2 to <4 hours with penicillin or ampicillin has 47% effectiveness, while <2 hours has 38% effectiveness, both significantly lower than the 91% effectiveness of ≥4 hours 4
• However, newborns exposed to any duration of intrapartum beta-lactams who are asymptomatic at birth are likely uninfected 5
• The 4-hour threshold remains the standard benchmark in current CDC guidelines 1, 2

Special Considerations for Penicillin-Allergic Mothers

For mothers with penicillin allergy not at high risk for anaphylaxis, cefazolin ≥4 hours before delivery is considered adequate prophylaxis. 1, 2

For mothers at high risk for anaphylaxis who received clindamycin or vancomycin, the effectiveness is uncertain and no data support a specific duration threshold. 1

• Clindamycin effectiveness is only 22%, significantly lower than beta-lactams 4
• These infants may warrant more intensive monitoring even if the mother received antibiotics for >4 hours 4

Critical Pitfalls to Avoid

Do not conflate duration of maternal antibiotics with number of doses—duration (≥4 hours) is the critical metric, not dose count. 1

• Duration of prophylaxis is more practical and more strongly associated with efficacy than number of doses 1

If signs of sepsis develop during the observation period, immediately conduct full diagnostic evaluation and initiate antibiotic therapy. 1

• Intrapartum antibiotic prophylaxis does not change the clinical spectrum of neonatal illness or delay onset of clinical signs among infants who develop GBS disease despite prophylaxis 1
• Over 90% of early-onset GBS disease presents within the first 24 hours of life 1

Do not provide routine prophylactic antibiotics to all newborns born to GBS-positive mothers who received adequate IAP—this promotes antibiotic resistance and unnecessary treatment. 2