Drug Therapy During Labor and Delivery, Part 1

Gerald G. Briggs; Stephanie R. Wan

Disclosures

Am J Health Syst Pharm. 2006;63(11):1038-1047. 

In This Article

Treatment of Chorioamnionitis

Chorioamnionitis is an infection of the amniotic fluid and its surrounding membrane (or placental tissues) that occurs before, during, or immediately after (within 24 hours) birth. It occurs in approximately 1-5% of term pregnancies and in as many as 25% of preterm deliveries.[39,40]

Chorioamnionitis is associated with maternal bacteremia and post-cesarean wound infection, neonatal sepsis, pneumonia, meningitis, and complications related to premature delivery, such as intraventricular hemorrhage and respiratory distress syndrome.[41] It is commonly associated with an ascending infection caused by organisms from the normal vaginal flora. Risk factors for developing chorioamnionitis include preterm labor, prolonged active labor, PROM, rupture of membranes greater than 12 hours, and maternal chronic autoimmune disease. Its diagnosis is typically made by clinical findings alone (maternal temperature, maternal and fetal tachycardia, uterine tenderness, or purulent amniotic fluid), in the absence of other signs of infection. In a majority of cases, an elevated maternal temperature may be the only symptom. Oftentimes, fetal heart rate changes (specifically tachycardia or variable decelerations) will accompany the diagnosis of chorioamnionitis, indicating the adverse fetal response to such an infectious environment. Laboratory confirmation (i.e., Gram's staining and culturing of amniotic fluid) for chorioamnionitis is usually not necessary before, and in fact may delay, initiation of treatment. Performing an amniocentesis for this purpose may only be indicated when chorioamnionitis is suspected at a gestational age remote from term. Once chorioamnionitis is diagnosed, expeditious delivery, along with empiric antibiotic administration, is the treatment of choice.[42]

Parenteral antibiotic treatment is aimed primarily toward the most common pathogens involved in chorioamnionitis, GBS, and E. coli. For this reason, ampicillin (2 g i.v. every 6 hours) plus gentamicin (1.5 mg/kg i.v. every 8 hours or per institution-specific pharmacy guidelines) is a common treatment regimen; clindamycin (900 mg i.v. every 8 hours) or metronidazole (500 mg i.v. every 8 hours) may be added to provide additional anaerobic coverage if cesarean delivery is performed.[42] In penicillin-allergic patients, vancomycin (1 g i.v. every 12 hours or per institution-specific pharmacy guidelines) may replace ampicillin. Single-agent broad-spectrum cephalosporins and extended-spectrum penicillins have not been shown to be superior to and are more expensive than the above-noted regimens.[35]

The duration of antibiotic therapy in chorioamnionitis should continue until the patient has been afebrile and asymptomatic for at least 24-48 hours postoperatively.[35] After vaginal delivery, antibiotics may be discontinued shortly after, usually within 24 hours of being afebrile. Evidence for shorter-course therapy also exists; a recent study of 292 patients with chorioamnionitis showed no difference in the primary outcome of postpartum maternal temperature between women who received antibiotics (ampicillin and gentamicin, plus clindamycin if delivered by cesarean section) until 24 hours afebrile and women who received just one additional dose of each after delivery.[43] In cases where chorioamnionitis is diagnosed before vaginal delivery, some clinicians will discontinue therapy once the baby is born. Outpatient oral antibiotics after treatment of chorioamnionitis or postpartum endometritis are rarely indicated.[42] If fever persists after 24 hours of starting the antibiotics, addition of a third agent (i.e., clindamycin, or metronidazole if not already added) should be considered. Special attention to local susceptibility reports is important to rule out the presence of treatment-resistant organisms. If the patient continues to be febrile, other sources for infection must be included in the differential diagnosis. Septic pelvic thrombosis, abscesses, wound infection, retained parts of conception, urinary tract infection, and vaginitis are examples of other sources to be ruled out.[35]

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