Fetal Heart Monitoring

Fetal Heart Monitoring

Alternate Names

  • external fetal monitoring
  • fetal heart rate tracing
  • intrapartum fetal monitoring
  • internal fetal monitoring

Definition

Fetal monitoring is the recording of the baby's heart rate and the mother's contractions during labor. Devices are connected to the mother's abdomen and to the baby.

Who is a candidate for the test?

The contractions of the uterus during labor decrease the amount of blood flowing to the placenta, the organ that normally attaches to the uterus, connecting the developing child to the mother and supplying nutrition and oxygen to the unborn baby.
Contractions also decrease the blood flow to the umbilical cord, which inserts into the developing baby's navel and connects the baby to the placenta. The decreased blood flow cuts down on the amount of oxygen getting to the baby.

Labor and delivery can be risky to the unborn child under normal conditions, but presents even more risk if the placenta is not functioning fully. In most hospital settings, the majority of women in labor undergo fetal monitoring to ensure a good outcome.

Conditions that require fetal monitoring include:
  • diabetes in the mother
  • intrauterine growth restriction, a condition in which the unborn child is not growing at an appropriate rate
  • past due pregnancy, of more than 42 weeks
  • preeclampsia, a toxic condition of pregnancy that may cause increased blood pressure, excessive swelling in the arms or legs, abnormal kidney function and disturbances in vision
  • eclampsia, a condition in which seizures develop in a woman with preeclampsia
  • chronic hypertension in the mother
  • multiple babies in the womb, such as twins or triplets
  • use of epidural anesthesia, a type of anesthesia in which the pain medication is given directly into the compartment that contains the spinal cord
  • use of drugs given to cause labor and delivery. These include oxytocin and prostaglandins.
  • suspected fetal distress
  • presence of green amniotic fluid due to meconium, or fetal bowel movement, which may cause meconium aspiration syndrome.
Electronic fetal monitoring can also be used to evaluate the strength of uterine contractions in cases such as:
  • preterm or early labor
  • placenta abruptio, a condition in which the placenta starts to detach from the wall of the uterus before the child is born
  • failure of labor to progress

How is the test performed?

Only external fetal monitoring is conducted if the fluid-filled membrane surrounding the fetus, known as the amniotic sac, has not broken. This is more common in early term or pre-term labor. The woman should lie on her left side if possible. This allows the maximum amount of blood to reach the infant.
For external electronic fetal monitoring, two belts are placed around the abdomen. One belt will monitor the baby's heartbeat. The other measures the strength and frequency of uterine contractions.
Internal monitors can be placed once the amniotic sac has broken. These provide may a more accurate picture of fetal distress during the progress of labor. Internal monitoring involves two devices.
The first is a small wire placed directly on the baby's scalp, called the fetal scalp electrode. It measures the baby's heart rate.
The second is an intrauterine pressure catheter. This is a narrow plastic tube inserted through the vagina, past the cervix and into the uterus. It is attached to a pressure gauge that measures the timing and strength of the uterus' contractions.
Both of these devices are attached to a computerized fetal monitor. This instrument converts the heart rate and uterine contractions into a readable graph chart.

What is involved in preparation for the test?

A woman should discuss the use of fetal monitoring with her healthcare professional during her prenatal visits in order to understand the risks and benefits of the testing.

What do the test results mean?

Fetal heart rate during labor varies. The normal range is from 120 to 160 beats per minute. Heartbeat speeds up and slows down slightly during and after a contraction.
Abnormal heartbeat patterns may indicate:
  • fetal distress. It can be either an ongoing problem or develop suddenly.
  • fever in either the woman or the unborn child. This usually indicates an infection.
  • an umbilical cord wrapped around the baby's neck or compressed during a contraction.
  • inability of the baby to withstand the stress of labor.
Abnormal uterine contraction patterns may indicate:
  • slow progress of labor. This may be due to dehydration or insufficient amounts of oxytocin, a medicine used to cause labor and delivery.
  • abnormally prolonged and intense contractions. This may be due to placenta abruptio or the use of too much oxytocin.
  • irritable uterus, or a uterus that contracts too frequently due to irritation. This may be the result of premature labor or fever.
Any of these results may require an immediate cesarean section or other form of intervention to prevent serious complication for mother or baby.

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