Recommended Strategies for
  Intrapartum Antimicrobial Prophylaxis (IAP)
  for Perinatal Group B Streptococcal Disease

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      Obstetric-care practitioners, in conjunction with supporting laboratories and labor and delivery facilities, should adopt the following strategy for the prevention of perinatal GBS disease based on prenatal screening for GBS colonization. The risk-based approach is no longer an acceptable alternative except for circumstances in which screening results are not available before delivery.


    • Colonization during a previous pregnancy is not an indication for intrapartum prophylaxis in subsequent deliveries. Screening to detect GBS colonization in each pregnancy will determine the need for prophylaxis in that pregnancy.
    • All pregnant women should be screened at 35--37 weeks' gestation for vaginal and rectal GBS colonization.

      Exceptions include:

      • Women who have previously given birth to an infant with invasive GBS disease should receive intrapartum chemoprophylaxis; prenatal culture-based screening is not necessary for these women
      • Women with GBS isolated from the urine in any concentration during their current pregnancy should receive intrapartum chemoprophylaxis. Prenatal culture-based screening at 35--37 weeks' gestation is not necessary for women with GBS bacteriuria.

    • Culture techniques that maximize the likelihood of GBS recovery are required for prenatal screening. If susceptibility testing is ordered for penicillin-allergic women, specimen labels should also identify the patient as penicillin allergic and should specify that if GBS is isolated, it should be tested for susceptibility to clindamycin and erythromycin. (Box 1)
    • Health-care providers should inform women of their GBS screening test result and the recommended interventions.


    • In the absence of GBS urinary tract infection, antimicrobial agents should not be used before the intrapartum period to treat GBS colonization. Such treatment is not effective in eliminating carriage or preventing neonatal disease and may cause adverse consequences.
    • Women with symptomatic or asymptomatic GBS urinary tract infection detected during pregnancy should be treated according to current standards of care for urinary tract infection during pregnancy.
    • GBS-colonized women who have a planned cesarean delivery performed before rupture of membranes and onset of labor are at low risk for having an infant with early-onset GBS disease. These women should not routinely receive intrapartum chemoprophylaxis for perinatal GBS disease prevention
      • Patients expected to undergo planned cesarean deliveries should nonetheless still undergo routine vaginal and rectal screening for GBS at 35--37 weeks because onset of labor or rupture of membranes may occur before the planned cesarean delivery. In rare situations in which patients or providers opt for intrapartum prophylaxis before planned cesarean deliveries, administration of antibiotics at the time of incision rather than at least 4 hours before delivery may be reasonable.


    • At the time of labor or rupture of membranes, intrapartum chemoprophylaxis should be given to all pregnant women identified as GBS carriers.
    • Women with known negative results from vaginal and rectal GBS screening cultures within 5 weeks of delivery do not require prophylaxis to prevent GBS disease even if any of the intrapartum risk factors develop (Table 1)

      Table 1. Indications for intrapartum antibiotic prophylaxis to prevent perinatal GBS disease under a universal prenatal screening strategy based on combined vaginal and rectal cultures collected at 35-37 weeks' gestation from all pregnant women
      Intrapartum prophylaxis indicated Intrapartum prophylaxis not indicated
    • Previous infant with invasive GBS disease.
    • GBS bacteriuria during current pregnancy
    • Positive GBS screening culture during current pregnancy (unless a planned cesarean delivery, in the absence of labor or amniotic membrane rupture, is performed)
    • Unknown GBS status (culture not done, incomplete, or results unknown) and any of the following:
    • Delivery at < 37 weeks gestation*
    • Amniotic membrane rupture >18 hours
    • Intrapartum temperature > 100.4 o F (> 38.0o C)**
    • Previous pregnancy with a positive GBS screening culture(unless a culture was also positive during the current pregnancy)
    • Planned cesarean delivery performed in the absence of labor or membrane rupture (regardless of maternal GBS culture status)
    • Negative vaginal and rectal GBS screening culture in late gestation during the current pregnancy, regardless of intrapartum risk factors
    • *If onset of labor or rupture of amniotic membranes occurs at < 37 weeks' gestation and there is a significant risk for preterm delivery (as assessed by the clinician), a suggested algorithm for GBS prophylaxis is provided (Table 2).
      **If amnionitis is suspected, broad-spectrum antibiotic therapy that includes an agent known to be active against GBS should replace GBS prophylaxis.

      Table 2. Sample algorithm for GBS prophylaxis for women with threatened preterm delivery. This algorithm is not an exclusive course of management. Variations that incorporate individual circumstances or institutional preferences may be appropriate.
      No GBS Culture
    • Obtain vaginal and rectal GBS culture and initiate IV penicillin.

      If culture is positive for GBS, then

    • Penicillin IV for > 48 hours (during tocolysis)
    • Intrapartum antibiotic prophylaxis at delivery

      If culture shows no growth after 48 hours, then stop penicillin

    • GBS Positive
    • Penicillin IV for > 48 hours
      (during tocolysis)
    • Intrapartum antibiotic prophylaxis at delivery
    • GBS Negative
    • No GBS prophylaxis
    • Penicillin should be continued for a total of at least 48 hours, unless delivery occurs sooner. At the physician's discretion, antibiotic prophylaxis may be continued beyond 48 hours in a GBS culture-positive woman if delivery has not yet occurred. For women who are GBS culture positive, antibiotic prophylaxis should be reinitiated when labor likely to proceed to delivery occurs or recurs.
    • If delivery has not occurred within 4 weeks, a vaginal and rectal GBS screening culture should be repeated and the patient should be managed as described, based on the result of the repeat culture.

       Recommended regimens for intrapartum antimicrobial
       prophylaxis for perinatal GBS disease prevention*

      Recommended Penicillin G, 5 million units IV initial dose, then
      2.5 million units IV every 4 hours until delivery
      Alternative Ampicillin, 2 g IV initial dose, then 1 g IV every 4 hours until delivery
      If penicillin-allergic
      Patients not at high risk for anaphylaxis Cefazolin 2 g IV initial dose, then
      1 g every 8 hours until delivery
      Patients at high risk for anaphylaxis
      GBS susceptible to clindamycin and erythromycin
      Clindamycin, 900 mg IV every 8 hrs until delivery

      Erythromycin, 500 mg IV every 6 hrs until delivery
      Patients at high risk for anaphylaxis
      GBS resistant to clindamycin or erythromycin or susceptibility unknown
      Vancomycin** 1 g IV every 12 hours until delivery

      * Broader-spectrum agents, including an agent against GBS, may be necessary for treatment of chorioamnionitis.

       History of penicillin allergy should be assessed to determine whether high risk for anaphylaxis is present. Penicillin-allergic patients at high risk for anaphylaxis are those who have experienced immediate hypersensitivity to penicillin (e.g., angioedema or urticaria) including a history of penicillin-related anaphylaxis; other high-risk patients are those with asthma or other diseases that would make anaphylaxis more dangerous or difficult to treat, such as persons being treated with beta-adrenergic-blocking agents.

       If laboratory facilities are adequate, clindamycin and erythromycin susceptibility testing (Box 1) should be performed on prenatal GBS isolates form penicillin-allergic women at high risk for anaphylaxis.

       Resistance to erythromycin is often but not always associate with clindamycin resistance. If a strain is resistant to erythromycin but susceptible to clindamycin, it may still have inducible resistance to clindamycin.

      **Cefazolin is preferred over vancomycin for women with a history of allergy other than immediate hypersensitivity reactions, and pharmacologic data suggest it achieves effective intraamniotic concentrations. Vancomycin should be reserved for penicillin-allergic women at high risk for anaphylaxis.




  • MMWR August 16, 2002 / 51(RR-11);1-22 .Prevention of Perinatal Group B Streptococcal Disease Revised
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    Created: 11/30/2002
    Updated: 1/30/2003