Final answer:
Early Decelerations are most often caused by fetal head compression, Variable Decelerations by umbilical cord compression, and Late Decelerations by uteroplacental insufficiency. Contractions of the uterus push the fetus out during birth, and the umbilical cord is cut to help the newborn transition to independent breathing.
Step-by-step explanation:
The most common causes of early, variable, and late decelerations relate to specific fetal heart rate patterns observed during labor. Each type of deceleration is associated with different physiological events.
- Early Decelerations are typically due to head compression during contractions, triggering a vagal response that leads to a temporary slowing of the heart rate.
- Variable Decelerations are usually caused by umbilical cord compression, resulting in a rapid decrease in heart rate with a variable recovery period.
- Late Decelerations are generally a sign of uteroplacental insufficiency, indicating that the fetus is not receiving adequate oxygen during contractions.
The terms like atrial depolarization, ventricular repolarization, ventricular depolarization, and atrial repolarization refer to different phases of the cardiac cycle and are not directly related to fetal heart decelerations.
Review Questions
1. The fetus is pushed out of the uterus during birth primarily due to the contractions of the uterine muscles, which are part of the birthing process.
2. The umbilical cord is cut before a newborn has started to breathe on its own to allow the newborn to transition from receiving oxygen via the placenta to breathing air independently.