Fetal bradycardia refers to an abnormally slow heart rate in a fetus and is usually temporary. Symptoms include a fetal heart rate of under 110 and slowed fetal movement. A major cause of this condition is medication taken during labor by the mother. These medications include narcotic analgesics, synthetic hormones and medications that are injected into the epidural space of the spinal cord to achieve pain relief.
Other causes for fetal bradycardia include maternal low blood pressure and compression of the umbilical cord. When the fetus does not get enough oxygen, it can cause fetal distress, leading to fetal bradycardia. When the mother lies on her back, pressure is exerted on a major blood vessel known as the superior vena cava. This can cut off fetal oxygen and result in a low heart rate. Many health care providers recommend that pregnant women avoid lying on their backs and endorse lying on their left when approaching the second trimester of pregnancy.
Sometimes umbilical compression and fetal bradycardia can become severe and even life-threatening. In these cases, an emergency Cesarean section might be indicated to restore oxygen to the baby and increase the heart rate. Monitoring of the fetal heart rate is typically done with either an internal or external fetal heart monitor. These monitors are routinely applied once the patient goes into labor and can detect even the subtlest of cardiac deviations.
When maternal narcotics are the cause of fetal bradycardia, certain medications can be administered to the mother to counteract the effects. These medications often work rapidly to normalized the fetal heart rate, but can sometimes cause side effects. Other causes of fetal bradycardia can include maternal medical conditions such as lupus. This autoimmune condition can cause cardiac arrhythmias in the fetus as well as the mother. Treating the underlying condition in the mother can often alleviate the arrhythmia in the fetus.
Congenital conditions can also cause a slow heart rate in the developing fetus. These include structural abnormalities and can often be detected by a medical diagnostic test known as an echocardiogram. This test uses sound waves, or ultrasound, to capture cardiac images in real time. The health care provider can determine if the heart is structurally sound by examining the chambers and valves, and he can also determine if the heart is contracting adequately to promote optimal circulation. Abnormal rhythms such as bradycardia and tachycardia, which is an abnormally high heart rate, can also be determined.