6 Fetal heart rate patterns

37. What is the normal fetal heart rate pattern during labour?

1. A baseline rate of 110–160 beats per minute
2. No decelerations during or after contractions

38. What is the importance of a normal fetal heart rate pattern?

A normal fetal heart rate pattern is reassuring as it suggests that the fetal condition is good. Fetal distress is very unlikely if the fetal heart rate pattern is normal.

39. Which fetal heart rate patterns are not normal during labour?

1. A baseline tachycardia
2. A baseline bradycardia
3. Early decelerations
4. Late decelerations
5. Variable decelerations

40. What is a baseline tachycardia?

A baseline fetal heart rate (between contractions) of more than 160 beats per minute.

41. What are the causes of a baseline tachycardia?

1. Maternal pyrexia
2. Maternal exhaustion
3. Salbutamol (Ventolin) administration
4. Chorioamnionitis (infection of the placenta and membranes)
5. Fetal haemorrhage or anaemia

42. What is a baseline bradycardia?

A baseline fetal heart rate (between contractions) of less than 110 beats per minute.

A baseline fetal heart rate of less than 110 beats per minute must be distinguished from the maternal heart rate. If the mother is asked to take a deep breath and then bear down as in delivery her heart rate, but not that of her fetus, will slow.

43. What is the cause of a baseline bradycardia?

A baseline bradycardia of less than 110 beats per minute usually indicates fetal distress which is caused by severe fetal hypoxia. If late decelerations are also present, a baseline bradycardia indicates that the fetus is at great risk of dying.

44. What are early decelerations?

Early decelerations are characterised by a slowing of the fetal heart rate starting at the beginning of the contraction, and returning to the baseline by the end of the contraction. Therefore the fetal heart rate during an early deceleration is slowest during the middle of the contraction. Early decelerations are usually due to compression of the fetal head during contractions. This causes the heart rate to slow during the contraction only.

Early decelerations only occur during the middle of a contraction.

45. What is the significance of early decelerations?

Early decelerations do not indicate the presence of fetal distress. However they may indicate very strong contractions. Therefore, these fetuses must be carefully monitored as they are at an increased risk of fetal distress.

46. What are late decelerations?

A late deceleration is a slowing of the fetal heart rate during a contraction, with the rate only returning to the baseline 30 seconds or more after the contraction has ended. They are present with every contraction.

Late decerations continue after the end of the contraction.

47. What is the significance of repeated late decelerations?

Repeated late decelerations are a sign of fetal distress and are caused by fetal hypoxia. The degree to which the heart rate slows is not important. The timing of the deceleration is what must be carefully observed. Late decelerations must always be taken seriously.

Repeated late decelerations indicate fetal distress.

48. What are variable decelerations?

Variable decelerations have no fixed time relationship to uterine contractions. Therefore, the pattern of decelerations changes from one contraction to another. Variable decelerations are usually caused by compression of the umbilical cord and do not indicate the presence of fetal distress. However, these fetuses must be carefully monitored as they are at an increased risk of fetal distress.

Variable decelerations are not easy to identify when a fetal monitor is used.

49. How should you assess the condition of the fetus on the basis of the fetal heart rate pattern?

1. The fetal condition is good (reassuring) if a normal fetal heart rate pattern is present.
2. The fetal condition is suspicious (non-reassuring) if the fetal heart rate pattern indicates that there is an increased risk of fetal distress.
3. The fetal condition is poor (abnormal) if the fetal heart rate pattern indicates fetal distress.

50. Which fetal heart rate patterns indicate an increased risk of fetal distress during labour?

1. A baseline tachycardia
2. Early decelerations

These fetal heart rate patterns do not indicate fetal distress but warn that the woman should be closely observed as there is an increased risk that fetal distress may develop. If electronic monitoring is available, all these high risk fetuses should be monitored continuously by CTG.

51. What fetal heart rate patterns indicate fetal distress during labour?

1. Repeated late decelerations
2. A baseline bradycardia

52. What questions should be asked when the fetal heart rate pattern is assessed during labour?

The fetal heart rate must be assessed before, during and after a contraction. The following questions must be answered and recorded on the partogram:

1. What is the baseline fetal heart rate?
2. Are there any decelerations?
3. If decelerations are observed, what is their relation to the uterine contractions?
4. If the fetal heart rate pattern is abnormal, how must the woman be managed?

53. What fetal heart rate pattern is abnormal during the second stage of labour?

Early decelerations occurring while the mother is pushing are common and do not necessarily indicate fetal distress. However, the baseline rate should benormal. A baseline bradycardia between contractions and before the mother pushes suggests fetal distress and is an indication for urgent delivery. The fetal heart rate should be normal before and after each bout of pushing.