FHT: Variable decelerations
Advanced, Clinical Subspecialties, Obstetric Anesthesia
Variable decelerations are the most common type of decelerations and are transient decreases in fetal heart rate that characteristically vary in duration, shape/magnitude, and timing/onset. They correspond with uterine contractions and are likely a result of umbilical cord compression against the fetus leading to decreased umbilical blood flow. They can be classified as mild (lasting <30 sec and FHR remains >80 bpm), moderate (FHR <80 bpm), or severe (lasting longer than 60 sec and FHR <70 bpm). Variable decelerations can lead to fetal asphyxia when severe or may progress to late decelerations or severe fetal bradycardia, both of which indicate the need for urgent intervention.