What intrapartum antibiotic prophylaxis is recommended for a pregnant woman with Group B Streptococcus colonization or risk factors, and how should the newborn be managed based on adequacy of prophylaxis, gestational age, and clinical signs?

Management of Group B Streptococcus Risk in Neonates

For pregnant women with GBS colonization, administer intravenous penicillin G (5 million units initial dose, then 2.5-3.0 million units every 4 hours) starting at least 4 hours before delivery, and manage the newborn based on a risk-stratified algorithm that considers adequacy of prophylaxis, gestational age, duration of membrane rupture, and clinical appearance. 1, 2

Intrapartum Antibiotic Prophylaxis for Mothers

First-Line Regimen

• Penicillin G is the preferred agent due to its narrow spectrum, universal GBS susceptibility, and proven efficacy 1
• Dosing: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery 1, 2
• Ampicillin (2g IV initial, then 1g IV every 4 hours) is an acceptable alternative but has broader spectrum activity 1, 2

Penicillin-Allergic Patients

• For non-severe penicillin allergy: Cefazolin 2g IV initial dose, then 1g IV every 8 hours until delivery 1
• For severe penicillin allergy: Obtain susceptibility testing for clindamycin and erythromycin on the GBS isolate 1
• If susceptible, use clindamycin 900mg IV every 8 hours until delivery 1
• Erythromycin is no longer acceptable due to increasing resistance 2
• Reserve vancomycin only when no other options exist 1

Critical Timing Requirement

• Adequate prophylaxis requires ≥4 hours of IV penicillin, ampicillin, or cefazolin before delivery 3, 2
• Only these three agents at this duration qualify as adequate prophylaxis for neonatal management purposes 3
• This 4-hour threshold achieves adequate fetal tissue levels and significantly reduces vertical transmission 2

Neonatal Management Algorithm

Well-Appearing Infants with Adequate Maternal Prophylaxis (≥4 hours)

• Observation for ≥48 hours with no routine diagnostic testing, regardless of gestational age 3
• Term infants (≥37 weeks) may be discharged home as early as 24 hours if discharge criteria met, ready access to medical care exists, and a responsible person will be present for home observation 3, 2
• If any signs of sepsis develop, immediately perform full diagnostic evaluation and initiate antibiotics 3

Well-Appearing Term Infants (≥37 weeks) with Inadequate/No Prophylaxis

If membrane rupture <18 hours:

• Observation for ≥48 hours with no routine diagnostic testing 3

If membrane rupture ≥18 hours:

• Limited evaluation (blood culture at birth, CBC with differential and platelets at birth and/or 6-12 hours) 3
• Observation for ≥48 hours 3

Well-Appearing Preterm Infants (<37 weeks) with Inadequate/No Prophylaxis

• Limited evaluation (blood culture, CBC with differential and platelets) plus observation for ≥48 hours, regardless of membrane rupture duration 3

Preterm Infants Born <35 Weeks' Gestation

Highest risk scenarios (requiring blood culture and empiric antibiotics even with adequate prophylaxis):

• Cervical insufficiency 3
• Preterm labor 3
• Premature rupture of membranes 3
• Intra-amniotic infection 3
• Acute or unexplained nonreassuring fetal status 3

Lower risk preterm scenarios (maternal/fetal indications like preeclampsia, fetal growth restriction):

• If adequate prophylaxis given and no labor/membrane rupture before cesarean delivery: no empiric antibiotics needed unless signs of sepsis 3
• If inadequate prophylaxis: administer empiric antibiotics 3
• Blood cultures are a reasonable option in these lower-risk preterm infants 3

Any Infant with Signs of Sepsis

• Full diagnostic evaluation immediately: blood culture, CBC with differential and platelets, chest radiograph if respiratory abnormalities present, lumbar puncture if stable enough and sepsis suspected 3
• Initiate antibiotic therapy immediately: IV ampicillin plus aminoglycoside for infants up to 7 days of age 3
• Broader-spectrum therapy if ampicillin resistance is a concern, particularly in very low birth weight infants 3

Maternal Chorioamnionitis

• Limited evaluation (blood culture, CBC) plus antibiotic therapy regardless of GBS prophylaxis status 3
• Consultation with obstetric providers is important as chorioamnionitis signs can be nonspecific 3

Alternative Risk Assessment Approaches

The 2020 AAP guidelines offer three options for managing well-appearing term and late-preterm infants (≥35 weeks) 3:

Multivariate Risk Assessment

• Use online calculators like the Neonatal Early-Onset Sepsis Calculator (https://neonatalsepsiscalculator.kaiserpermanente.org/) 3
• Enter a previous probability of 0.5 per 1,000 (national risk) unless local incidence known 3
• Only penicillin, ampicillin, and cefazolin count as specific for GBS treatment when using these calculators 3

Clinical Condition-Based Assessment

• Good clinical condition at birth in term infants reduces early-onset infection risk by 60-70% 3
• Infants born after insufficient prophylaxis or maternal intrapartum temperature ≥100.4°F should be monitored for 36-48 hours 3

Clinical Presentation to Monitor

Early-Onset GBS Disease (First 7 Days)

• Tachycardia, tachypnea, lethargy 3
• Can progress to severe cardiorespiratory failure, persistent pulmonary hypertension, perinatal encephalopathy 3

Late-Onset GBS Disease (After 7 Days)

• Most commonly presents as bacteremia without focus 3
• Temperature ≥100.4°F, lethargy, poor feeding, irritability, tachypnea, grunting, apnea 3
• Meningitis signs: irritability, vomiting, temperature instability, bulging fontanelle, seizures 3
• Can cause discrete infections: pneumonia, bone/joint infections, cellulitis, adenitis 3

Critical Pitfalls to Avoid

• Do not use oral antibiotics to treat GBS colonization outside of active labor—this is ineffective in eliminating carriage and promotes resistance 1
• Do not delay medically necessary obstetric procedures solely to achieve 4 hours of prophylaxis 2
• Many EOGBS cases occur in infants whose mothers screened GBS-negative, so remain vigilant for sepsis signs in all newborns 4
• Procedural errors include failure to recognize documented GBS colonization or failure to evaluate infants with intrapartum risk factors 4
• Infants with intrapartum clinical risk factors require evaluation even when mothers screened GBS-negative 4