Fetal Heart Monitoring
Alternate Names : External Fetal Monitoring, Fetal Heart Rate Tracing, Intrapartum Fetal Monitoring, Internal Fetal Monitoring
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.
This is done in two ways:
External monitoring uses external belts around the mother's abdomen.
Internal monitoring involves placing a monitor electrode on the baby's scalp. A thin tube or catheter is also inserted into the uterus via the vagina to monitor contractions.
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 fetus to the mother and supplies nutrition and oxygen to the fetus. Contractions also decrease the blood flow to the fetal umbilical cord, which inserts into the developing baby's belly button and connects the fetus 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 fetus 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 retardation, a condition in which the fetus 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 fetuses, 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.
Fetal monitoring is also used to evaluate the strength of uterine contractions in cases such as:
preterm or early labor
placenta abruptio, a condition in which the placenta detaches from the wall of the uterus at an inappropriately early time
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. 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. Internal monitors provide a more accurate picture of 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.