Do you give antibiotics intravenously prior to a normal spontaneous (vaginal) delivery?

Intravenous Antibiotics Prior to Normal Spontaneous Vaginal Delivery

Intravenous antibiotics are NOT routinely given to all women prior to normal spontaneous vaginal delivery—they are selectively administered during labor only to women who meet specific high-risk criteria for Group B Streptococcus (GBS) colonization or infection. 1

Universal Screening Approach

All pregnant women should undergo vaginal-rectal GBS screening at 36 0/7 to 37 6/7 weeks' gestation (updated from the previous 35-37 week window). 2 The screening involves a single swab taken first to the vagina and then through the anal sphincter to the rectum. 3

Who Receives Intrapartum Antibiotic Prophylaxis

Intravenous antibiotics during labor are indicated for women with:

• Positive GBS screening culture at 36-37 weeks' gestation 1, 3
• GBS bacteriuria at any concentration during the current pregnancy (regardless of colony-forming units) 3, 4
• Previous infant with invasive GBS disease 3
• Unknown GBS status at term (≥37 weeks) with membrane rupture >18 hours 3
• Preterm labor or rupture of membranes (<37 weeks) with unknown or positive GBS status 1
• Intrapartum fever with signs of chorioamnionitis (regardless of GBS status) 3

Who Does NOT Receive Prophylaxis

Women undergoing planned cesarean delivery before labor onset with intact membranes do NOT require routine GBS prophylaxis, regardless of colonization status, because the risk of transmission is extremely low in this specific circumstance. 1 However, these women should still undergo routine screening at 36-37 weeks because labor or membrane rupture may occur before the planned procedure. 1

Recommended Antibiotic Regimens

First-Line Therapy

• Penicillin G: 5 million units IV initially, then 2.5 million units IV every 4 hours until delivery 4, 1
• Ampicillin: 2 g IV initially, then 1 g IV every 4 hours until delivery 4, 1

Penicillin G is preferred due to its narrower antimicrobial spectrum, which reduces selection pressure for resistant organisms. 1

For Penicillin-Allergic Patients (Non-Anaphylaxis Risk)

• Cefazolin: 2 g IV initially, then 1 g IV every 8 hours until delivery 4, 2

For Severe Penicillin Allergy (High Anaphylaxis Risk)

• Clindamycin: 900 mg IV every 8 hours (only if isolate confirmed susceptible) 4, 2
• Vancomycin: 1 g IV every 12 hours (if susceptibility unknown or clindamycin-resistant) 4, 2

Susceptibility testing must be performed on GBS isolates from women with significant penicillin allergy to guide appropriate alternative therapy. 3, 4

Timing and Duration

Antibiotics should be administered at least 4 hours before delivery to achieve optimal prevention of vertical GBS transmission and early-onset neonatal disease. 1 This duration allows adequate antibiotic levels in fetal circulation and amniotic fluid. 1 Shorter durations (≥2 hours) may provide some protection but are less effective. 1

Effectiveness

Intrapartum antibiotic prophylaxis reduces early-onset GBS disease by 86-89% when administered appropriately. 1, 5 Early clinical trials demonstrated near 100% efficacy, with subsequent real-world effectiveness remaining very high. 1 This strategy has prevented an estimated 70,000 cases of early-onset GBS disease in the United States from 1994 to 2010. 5

Critical Pitfalls to Avoid

• Do NOT treat asymptomatic GBS vaginal colonization with antibiotics outside of labor—prenatal antibiotic treatment does not eliminate colonization, does not prevent neonatal disease, and may promote antibiotic resistance. 4, 6
• Do NOT withhold screening from women planning cesarean delivery—they remain at risk if labor begins or membranes rupture before the scheduled procedure. 1
• Do NOT assume negative cultures remain valid indefinitely—GBS screening results are only valid for 5 weeks. 1
• Do NOT use oral or intramuscular antibiotics for prophylaxis—only intravenous administration during labor has proven effective. 1

Special Considerations for Preterm Delivery

For women with threatened preterm delivery (<37 weeks), initiate GBS prophylaxis immediately while obtaining vaginal-rectal cultures, then continue if true labor progresses or discontinue if labor is successfully arrested. 1 Antibiotics given for latency prolongation in preterm premature rupture of membranes (ampicillin 2 g IV, then 1 g IV every 6 hours for 48 hours) provide adequate GBS coverage. 1