Welcome back to another episode of the OB/GYN Resident Survival Guide. In today’s episode, we’re reviewing intraamniotic infection—formerly known as chorioamnionitis. Throughout this episode, I’ll use the abbreviation IAI to refer to intraamniotic infection.

IAI is defined as infection of the placenta, amniotic fluid, membranes, decidua, and/or fetus. It most commonly develops when microorganisms from the lower genital tract ascend into the amniotic cavity which is normally sterile. Less commonly, it can occur following invasive procedures such as amniocentesis, chorionic villus sampling, or cerclage placement, or via hematogenous spread during systemic maternal infection.

Although intraamniotic infection is relatively uncommon, it’s critical to recognize and treat promptly because it carries significant risks for both maternal and neonatal outcomes. Maternal complications include dysfunctional labor, postpartum hemorrhage, endometritis, and sepsis, which may progress to ARDS, septic shock, or death. Neonates exposed to IAI are at increased risk for pneumonia, meningitis, cerebral palsy, bronchopulmonary dysplasia (particularly in preterm infants), and sepsis, with associated morbidity and mortality.

Risk Factors for Intraamniotic Infection

Several factors increase the risk of developing IAI, including prolonged labor and prolonged rupture of membranes (typically defined as rupture lasting 18 hours or more). Additional risk factors include nulliparity, use of intrauterine monitors such as fetal scalp electrodes (FSE) or intrauterine pressure catheters (IUPC), preexisting lower genital tract infections or sexually transmitted infections, meconium-stained amniotic fluid, and GBS colonization.

Historically, frequent digital cervical exams have also been considered a risk factor. Interestingly, a 2012 study evaluating over 2,000 laboring patients found no association between exam frequency and intrapartum fever, regardless of membrane status. While this represents only one study, its size and relatively recent publication make it worth noting.

Diagnosis of Intraamniotic Infection

Definitive diagnosis of IAI requires analysis of amniotic fluid or pathologic evaluation of the placenta. In clinical practice, however, treatment is initiated based on clinical suspicion rather than invasive testing.

Suspected IAI is diagnosed when one of the following is present:

A single maternal temperature of 39°C (102.2°F) or higher
A maternal temperature of 38.0–38.9°C (100.4–102.1°F) plus at least one of the following:
- Maternal leukocytosis
- Fetal tachycardia
- Purulent cervical drainage

If the maternal temperature reaches 39°C or higher, treatment for IAI should be initiated even in the absence of additional findings.

Management of Intraamniotic Infection

Management centers on rapid initiation of intravenous antibiotics and treatment of maternal fever with antipyretics such as acetaminophen. Early antibiotic therapy reduces neonatal infection risk, decreases maternal morbidity related to fever, and is associated with shorter maternal hospital stays.

Many institutions also activate maternal sepsis protocols when IAI is suspected. These often mirror standard adult sepsis pathways and may include IV fluid resuscitation, laboratory evaluation (CBC with differential, blood cultures, lactate, electrolytes), and more frequent vital sign monitoring.

It’s also essential to notify pediatrics or the NICU team so they can be present at delivery and assess the newborn.

Antibiotic Regimens

Standard treatment consists of IV ampicillin and IV gentamicin. For patients with penicillin allergy, gentamicin is typically continued while ampicillin is replaced with cefazolin, clindamycin, or vancomycin depending on allergy severity.

High-risk penicillin allergies—such as prior hives, flushing, angioedema, or anaphylaxis—generally warrant use of clindamycin or vancomycin rather than cefazolin. ACOG Committee Opinion 797 provides a helpful table outlining antibiotic selection based on allergy type.

Duration of Therapy

At minimum, antibiotics should be continued through labor. For patients who deliver vaginally, antibiotics may be discontinued after delivery. For those who undergo cesarean delivery, one additional postoperative dose is recommended due to the increased baseline risk of endometritis associated with uterine instrumentation.

If fevers persist postpartum, or if there is concern for sepsis or bacteremia, extended antibiotic therapy is appropriate regardless of delivery mode. As with other infections, source control is key—in this setting, delivery of the fetus and placenta—but clinical improvement may take time even after delivery.

Key Takeaways

Intraamniotic infection involves infection of the placenta, membranes, amniotic fluid, decidua, and/or fetus. Diagnosis is based on maternal fever alone (≥39°C) or fever between 38–38.9°C with additional clinical findings such as leukocytosis, fetal tachycardia, or purulent cervical drainage. Management includes prompt IV antibiotics, antipyretics, sepsis protocols when indicated, and early involvement of pediatrics. Standard therapy is ampicillin and gentamicin, with alternatives guided by penicillin allergy status and clinical severity.

That’s it for today, I’ll see you next week with another episode!