A new emphasis on interpretative systems and recommended management strategies, as set forth by the recent 2008 joint workshop, is also included and reviewed in detail. Fundamental Principles When Using NICHD Terminology6 A set of overarching operational principles was sellckchem outlined prior to presenting the actual definitions of terms integral to the interpretation of cardiotocography. The most germane principles are: Although the development of computerized interpretation programs is underway, the definitions are to be used for visual interpretation of CTG. The definitions apply to patterns produced from either an external Doppler ultrasound device or a direct transcervical fetal electrode detecting the fetal electrocardiogram. The documentation of both CTG and tocodynamometry should be of adequate quality for visual interpretation.

The chief emphasis is on intrapartum patterns, although the definitions are applicable to antepartum observations. The patterns to be defined are categorized as either baseline, periodic, or episodic. Periodic patterns are associated with contractions, whereas episodic patterns are independent of uterine contractions. Periodic patterns are distinguished based on waveform, with accelerations or decelerations defined as abrupt versus gradual onset in relation to the adjacent baseline CTG. No differentiation is made between short-term variability (or beat-to-beat variability or R-R wave period differences in the electrocardiogram) and long-term variability because in practice, they are visually determined as a unit.

The definition of variability is based visually on the amplitude of the complexes, with exclusion of the regular, smooth sinusoidal pattern. CTG patterns are gestational age-dependent and can differ based on fetal physiologic status and maternal physiologic status, making each of these critical interpretive factors in the evaluation of a CTG pattern. Maternal medical status, prior fetal assessments, use of medications, and other factors also warrant consideration. The individual components of CTG that are defined do not occur in isolation and generally evolve over time. A full description of a CTG requires a qualitative and quantitative description of uterine contractions, baseline fetal heart rate, baseline CTG variability, presence of accelerations, periodic or episodic decelerations, and changes or trends of CTG patterns over time.

Uterine Contractions6 The number of contractions present in a 10-minute window, averaged over 30 minutes, is the manner by which uterine contractions are quantified. When assessing uterine activity, equal importance should be given to contraction frequency, duration, intensity, and relaxation time between contractions. GSK-3 Normal uterine contractions are 5 contractions or less in 10 minutes, averaged over a 30-minute window. Tachysystole is defined as more than 5 contractions in 10 minutes, averaged over a 30-minute window.