Master Acceleration and Deceleration with VEAL CHOP

A variable deceleration is characterized by an abrupt decrease in FHR below the baseline with the onset to lowest point (nadir) less than 30 seconds. They can occur any time during the contraction cycle and last at least 15 seconds. They happen in approximately half of all labors and are usually transient and correctable. They have a characteristic U, V, or W shape on the fetal monitor and are noted by their rapid descent and ascent from the lowest point (nadir) of the deceleration.

Variable decelerations can occur at any time during uterine contractions and are caused by compression of the umbilical cord often because of an abnormal cord position. The umbilical cord can get wrapped around the fetal neck, chest, arm, or leg. When the cord is between the fetus and maternal pelvis, it can lead to compression.

An early deceleration is identified as a gradual decrease (onset to lowest point is ≥ 30 seconds) in fetal heart rate with return to the baseline associated with a contraction. These are most commonly associated with compression of the fetal head and is often considered a normal finding with no intervention required other than continued monitoring.

Head compression, especially during uterine contractions, is the most common cause of an early deceleration that occurs during labor as the fetal head advances in the birth canal. This compression can be correlated to uterine contractions, vaginal examinations, applying pressure to the fundus, and the placement of internal monitoring instruments.

Increases of the fetal heart rate of at least 15 beats per minute above baseline that start and peak within 30 seconds, but not less than 15 seconds are termed accelerations. These should subside within 2 minutes. Accelerations are common and are associated typically with any direct or indirect fetal movement. Accelerations are used as an indicator of fetal well being.

Accelerations are often used as a measure of fetal well being and normal acid base balance.

A late deceleration is a gradual decrease of the FHR during the contraction with the lowest point (nadir) occurring after the peak of the contraction. It does not return to the FHR baseline until after the contraction is over. They correspond with placental insufficiency.

When there is insufficient oxygenation between the placenta and fetus, uteroplacental insufficiency occurs and causes late decelerations. This can occur due to conditions such as uterine tachysystole, which happens when there are more than 5 contractions in 10 minutes. Frequent contractions do not allow sufficient recovery and adequate oxygen exchange in the placenta. Other conditions are maternal supine hypotension, placental previa, hypertensive disorders, diabetes mellitus, intraamniotic infection, intrauterine growth restriction, epidural or spinal anesthesia, and postmaturity.