IAI & Preterm Labor: A serious cause with serious consequences

Intraamniotic infection (IAI) is a serious infection of the amniotic fluid and surrounding fetal membranes. These infections may be dangerous and dramatically increase the risk of infant mortality and morbidity as well as increase the risk of maternal infectious complications, mortality and morbidity.

Recently, IAI has been identified as a major cause of preterm birth. IAI accounts for 50% of preterm deliveries before 30 weeks, and is also associated with 20 to 40% of cases of early onset neonatal sepsis and pneumonia.^4,5

IAI is a serious infection of the amniotic fluid and surrounding fetal membranes.

This infection creates a toxic environment for the fetus; the longer the baby remains untreated, the more serious the potential outcome. The most devastating complications are stillbirth and neonatal death.

These infections are often subclinical with vague or no symptoms before the sudden onset of preterm labor. The risk of IAI in association with preterm labor is inversely related to gestational age—the earlier the onset of preterm labor, the more likely that infection is behind it. IAI is less common beyond 34 weeks of gestation.

Appropriate management of preterm labor requires knowledge of whether or not there is intraamniotic infection. Unfortunately, preterm labor associated with intraamniotic infection typically does not respond to conventional treatments for preterm labor with tocolytic drugs which are used to slow or stop labor. Such treatment can cause significant maternal complications, such as pulmonary edema if used when IAI is present. In addition, most cases of preterm labor caused by IAI have been shown to deliver within one to seven days.

By clearly identifying IAI, appropriate therapy can be initiated—administration of broad-spectrum antibiotics to the mother, transport of the mother to a delivery location with an appropriate level Neonatal Intensive Care Unit (NICU) and facilitating timely delivery of the baby for observation and treatment. Broad-spectrum antibiotics have been shown to reliably cross the placenta and reduce the risk of neonatal sepsis associated with IAI (compared to starting therapy after birth). There is also experimental evidence in animal models that treatment of intraamniotic infection with antibiotics and other immune modulators prolongs gestation and improves pregnancy outcome.^6,7,8

Antibiotics are effective, but they don’t stop the clock. Timely diagnosis is truly needed to allow better patient management, and better outcomes for mothers and their babies.

The Diagnostic Dilemma: Amnio or no amnio?

Ideally, amniocentesis is performed in cases of early preterm labor to identify the presence or absence of IAI so that the appropriate treatment can be followed. Amniocentesis is a procedure that is performed using a needle inserted into the uterus through the abdominal wall to collect amniotic fluid. The amniotic fluid is then subjected to a series of laboratory tests—cultures, Gram stain, glucose concentration—to identify microorganisms causing infection.

Despite recent guidance encouraging use of amniocentesis to diagnose IAI in cases of preterm labor, physicians find it difficult to consistently perform amniocentesis due to a number of different factors. Recent research conducted by the Pregnancy Research Center showed that while many physicians feel it is important to rule in/rule out IAI, the perceived risks associated with the amniocentesis procedure may outweigh the perceived benefit. In addition, many patients will refuse the procedure when recommended due to anxiety about risk to the fetus. Further compounding the limitations associated with performing amniocentesis in these urgent cases is the 48-hour timeframe needed to perform the cultures—clearly limiting their usefulness in helping to guide the physician’s clinical decision making when faced with the emergent need to slow or stop preterm labor. The other lab tests conducted on the amniotic fluid obtained by amniocentesis, e.g. Gram stain & glucose concentrations, have low sensitivity for detecting infection of the amniotic cavity.  For more information, visit Pregnancy Research Center.

Better management of preterm labor requires improved tools to diagnose IAI. There is a significant need for non-invasive diagnostics with a turnaround time that can guide clinical decision making about appropriate treatment to improve both short- and long-term outcomes.