Washington, DC -- Refinements of the definitions, classifications, and interpretations of fetal heart rate (FHR) monitoring methods were issued today in new guidelines released by The American College of Obstetricians and Gynecologists (ACOG). The objective of the guidelines is to reduce the inconsistent use of common terminology and the wide variability that sometimes occurs in FHR interpretations. ACOG's Practice Bulletin, published in the July 2009 issue of Obstetrics & Gynecology, supports the recommendations of the Eunice Kennedy Shriver National Institute of Child and Health Development workshop* on electronic fetal monitoring (EFM) held in April 2008.
The intent of FHR monitoring is to help keep an eye on the status of the fetus during labor and intervene if necessary. There are two main FHR monitoring methods. The most commonly used method is EFM, which detects the fetal heart rate and the length of uterine contractions and the time between them. EFM allows physicians and nurses to measure the response of the fetal heart rate to uterine contractions. A lesser-used method is manual auscultation, which employs either a small handheld Doppler device or a fetoscope (similar to a stethoscope). A normal fetal heart varies between 110 and 160 beats per minute. A heart rate that doesn't vary or is too low or too high may signal a potential problem with the fetus.
"Since 1980, the use of EFM has grown dramatically, from being used on 45% of pregnant women in labor to 85% in 2002," says George A. Macones, MD, who headed the development of the ACOG document. "Although EFM is the most common obstetric procedure today, unfortunately it hasn't reduced perinatal mortality or the risk of cerebral palsy. In fact, the rate of cerebral palsy has essentially remained the same since World War II despite fetal monitoring and all of our advancements in treatments and interventions."
One notable update in the guidelines is the three-tier classification system for FHR tracings (print-outs of the fetal heart rate). Category 1 FHR tracings are considered normal and no specific action is required. Category 2 tracings are considered indeterminate. This category requires evaluation and surveillance and possibly other tests to ensure fetal well-being. Category 3 tracings are considered abnormal and require prompt evaluation, according to ACOG. An abnormal FHR reading may require providing oxygen to the pregnant woman, changing the woman's position, discontinuing labor stimulation, or treating maternal hypotension, among other things. If the tracings do not return to normal, the fetus should be delivered.
"Our goal with the ACOG guidelines was to define existing terminology and narrow definitions and categories so that everyone is on the same page," says Dr. Macones. One of the problems with FHR tracings is the variability in how they're interpreted by different people. The ACOG guidelines highlight a case in which four obstetricians examined 50 FHR tracings; they agreed in only 22% of the cases. Two months later, these four physicians reevaluated the same 50 FHR tracings, and they changed their interpretations on nearly one out of every five tracings.
A meta-analysis study shows that although EFM reduced the risk of neonatal seizures, there is still an unrealistic expectation that a nonreassuring FHR can predict the risk of a baby being born with cerebral palsy. The false-positive rate of EFM for predicting cerebral palsy is greater than 99%. This means that out of 1,000 fetuses with nonreassuring readings, only one or two will actually develop cerebral palsy. The guidelines state that women in labor who have high-risk conditions such as preeclampsia, type 1 diabetes, or suspected fetal growth restriction should be monitored continuously during labor.
Practice Bulletin #106, "Intrapartum Fetal Heart Rate Monitoring: Nomenclature, Interpretation, and General Management Principles," is published in the July 2009 issue of Obstetrics & Gynecology.
* In 2008, The Eunice Kennedy Shriver National Institute of Child Health and Human Development partnered with ACOG and the Society for Maternal-Fetal Medicine to sponsor a workshop focused on EFM.
The American College of Obstetricians and Gynecologists (ACOG) is the nation's leading group of physicians providing health care for women. As a private, voluntary, nonprofit membership organization of approximately 56,000 members, ACOG: strongly advocates for quality health care for women; maintains the highest standards of clinical practice and continuing education of its members; promotes patient education; and increases awareness among its members and the public of the changing issues facing women's health care.