Variability therefore,Р’В is the single most important indicator of an adequately oxygenated fetus. Conditions that alter theР’В integrity of this neuro-cardiac axis, such as hypoxemia,Р’В result in loss of heart rate variability. The interaction between these systems results in a difference in the beat-to-beat intervals resulting in variability of the fetal heart rate tracing.Р’В In the term fetus, moderate variability is considered normal as it indicates a normally functioning central nervous system. These systems exert their control via the cerebral cortex, the medulla oblongata, the sympathetic ganglia and the vagus nerve. In the normal fetus, there is an interplay between the sympathetic (acceleration) and parasympathetic (deceleration) nervous systems in the control of heart rate.

Marked: amplitude range greater than 25 beats per min (NICHD).

Moderate (normal): amplitude range 6-25 beats per min.

Minimal: amplitude range detectable but 5 beats per min or fewer.

Variability is visually quantitated as the amplitude of peak-to-trough in beats per min.

Fluctuations in the FHR of 2 cycles per min or greater.

Parasympathetic tone becomes more dominant with advancing gestational age, and a post-term fetus may have a FHR between 110-120 beats/min.

The baseline FHR is normally set by the atrial pacemaker and the beat-to-beat differences in the heart rate are governed by a balance between the sympathetic and parasympathetic branches of the autonomic nervous system.Р”Р„s the central nervous system matures, the baseline FHR gradually drops, and the normal ranges for a mid-trimester fetus are between 150-170 beats/min. The normal FHR baseline should range between 110 beats/min to 160 beats/min. All changes are therefore, based on a deviation from that fetusРІР‚в„ў resting norm. In order to determine whether there are changes in the fetusРІР‚в„ў physiologic status, a baseline heart rate must first be determined as a reference. The baseline must be for a minimum of 2 min in any 10-min segment (NICHD).Segments of baseline that differ by more than 25 beats per min.The mean FHR rounded to increments of 5 beats per min during a 10 min segment, excluding: Uterine contractions are dealt with at the end of this section.Р”Вemonstrated below is a picture from a typical EFM display and a sample EFM strip. Also, because uterine contractions can affect placental exchange, evaluation of contraction patterns may provide clues as toР’В the potential effects of the contraction rate and force on the fetus. Uterine contraction patterns can provide information about the progress of labor. In addition to monitoring fetal heart rate patterns, information about the effects of labor on the fetus can also be learned by observing the pattern of uterine contractions. Identify changes or trends in FHR patterns over time.

Determine the presence of accelerations or decelerations from baseline.

Identify the baseline fetal heart rate and presence of variability.

Identify the type of monitor used РІР‚вЂњ external versus internal: second generation versus first generation.Evaluate the recording: is it continuous and adequate for interpretation?.To appropriatelyР’В interpret a fetal monitoring tracing, theР’В systematic approach below should be followed: These definitions and descriptions are the terminology used by the National Institute of Child Health and Human Development and have been adopted by the American College of Obstetrics and Gynecology (ACOG) and the Association of WomenРІР‚в„ўs Health, Obstetric, and Neonatal Nurses (AWHONN). These areas include fetal heart rate patterns with specific definitions and descriptions. Changes or trends of FHR patterns over time.In order to accurately assess a FHR pattern, a description of the pattern should include qualitative and quantitative information in the following five areas: Accurate fetal heart rate (FHR)Р’В assessment may help in determining the status of the fetus and indicate management steps for a particular condition.

Marked variability