Glossary of Terms
Glossary of Terms
1. Early decelerations are normal and common. These decelerations are called early because they occur early during a uterine contraction. These FHR decelrations usually occur after labor is well established (4-7 cm of cervical dilatation). The FHR rarely goes below 100 beats per minute. The cause of these decelerations is head compression during uterine contractions.
2. Late decelerations cause more concern. They are called late because they first appear at or after the peak of the uterine contraction. The FHR improves only after the contraction has stopped. These FHR decelerations may be mild or severe based on how low the FHR goes and how long it takes for the FHR to recover. It is thought to be caused by reduced blood flow to the uterus and placenta during a during a contraction.
3. Variable decelerations are a common type of FHR deceleration in labor and are caused by umbilical cord compression. Up to 80% of fetuses will have variable decelerations during labor. the significance of the these decelerations depends on how low the heart rate drops and how long the episode lasts.
When referring to a newborn baby bradycardia is usually associated with apnea or cessation of breathing. Apnea and bradycardia spells are most common in prematurely born infants. During these spells the infant will stop breathing for at least 15 seconds and the heart rate will start to slow. Gentle touching or other stimulation almost always restarts the breathing and increases the heart rate. Medications (theophylline or caffeine) are often used to treat these spells in newborn babies. Apnea of prematurity does not cause sudden infant death syndrome (SIDS). However, prematurely born babies are at greater risk for SIDS, just not because of apnea of prematurity. The exact reasons why premature babies have a higher risk of SIDS is not known.