Introduction
Hearing the heartbeat of the baby is a thrilling experience for the parents. It can be detected by the vaginal ultrasound as early as six weeks after gestation, and the heart rate keeps changing till birth.
When Can Baby's Heartbeat Heared First?
The fluttering of cells can be heard and seen for the first time when the mother is about six weeks pregnant during an early ultrasound exam. Otherwise, the baby's heartbeat can be first heard with a fetal doppler at a regular prenatal check-up. The sound can be heard depending on the baby's position in the uterus, the weight, and the accuracy of the due date. The health care provider may be able to hear it with the doppler as early as 12 weeks. Checking the baby's heartbeat will become a regular routine in every prenatal visit.
What Is the Device Used to Listen to a Baby's Heartbeat?
1) Doppler - A fetal doppler, called Daptone, uses sound waves to check the baby's heartbeat. A handheld device is used to detect changes in movement that are represented as sound. A fetal Doppler test normally takes place during the second trimester. The device is covered with ultrasound gel and moved around the belly until a spot is found where the heartbeat can be detected. The doppler forwards and receives sound waves that bounce from the baby's heart. This way, the fetal Doppler makes the baby's heartbeats loud enough to hear.
2) Stethoscope - A stethoscope is a medical tool that amplifies internal noises, like the heart and lungs. Depending on factors like the mother's weight, the location of the placenta, and the baby's position, the baby's heartbeat can be heard at about 18 to 20 weeks.
3) Fetoscope - The fetoscope is a combination of the stethoscope and the Pinard horn. It does not use ultrasound. It is designed in such a way that the practitioner's forehead is used to conduct sound, which often gives better results. Using this device requires skill. The heartbeat sounds like a watch under a pillow, and the placenta produces a whooshing sound.
What Are the Methods of Monitoring a Baby's Heartbeat?
The average heart rate of a fetus is between 110 and 160 beats per minute. It can differ by 5 to 25 beats per minute. There can be changes in fetal heart rate depending on the conditions of the uterus. An abnormal fetal heart rate may happen if the fetus does not get enough oxygen or due to other problems.
There are two methods of monitoring fetal heart rate, that includes:
-
External Fetal Heart Monitoring - In this method, a device is used to listen to and record the baby's heartbeat through the abdomen. It counts the baby's heart rate during prenatal and labor visits. The baby's heart rate is continuously checked during labor and birth, and this is done with the help of the ultrasound probe fastened to the mother's belly. It sends the sounds of the baby's heart to a computer, and then the rate and pattern of the baby's heart rate are displayed on a screen and printed on paper.
-
Internal Fetal Heart Monitoring - In this method, a thin wire (electrode) is put on the baby's scalp. The wire runs from the baby through the cervix and is connected to the monitor. This method provides better readings because things like movement do not affect it. But it can only be done if the amniotic sac (the fluid surrounding the baby) has ruptured and the cervix is opened. The doctors may use this method when external monitoring is not giving a correct reading or to watch the baby more closely during labor.
What Is the Importance of Fetal Heart Rate Monitoring?
Fetal heart rate monitoring is helpful in high-risk pregnancies like diabetes or high blood pressure. It is also used to check how preterm labor medicines affect the baby. These medicines are used to keep labor from starting too early.
Fetal heart rate monitoring is also used in other tests, including:
-
Nonstress Test - This measures the fetal heart rate as the baby moves.
-
Biophysical Profile (BPP) - This test combines a nonstress test and ultrasound.
-
Contraction Stress Test - This test measures the fetal heart rate and uterine contractions.
Factors that may affect the fetal heart rate during labor:
-
Uterine contractions.
-
Tests were done during labor.
-
Pain medicines or anesthesia are given during labor.
-
Pushing during the second stage of labor.
What Are Fetal Arrhythmias or Dysrhythmias?
A healthy fetus has a heartbeat of 120 to 160 beats per minute, beating at a regular rhythm. Arrhythmia most often refers to an irregular heartbeat, while dysrhythmia represents all types of abnormal heartbeats; the heartbeat can be either too fast (tachycardia) or too slow (bradycardia).
How Is the Development of a Baby's Heart?
Fetal heart development begins early in pregnancy, and the baby's heartbeat continues to change even after birth so that the baby can adjust outside the womb.
First-Trimester Development
-
Week 4 - A distinct blood vessel will be formed inside the embryo, which will develop into the baby's heart and blood system in the future.
-
Week 5 - The developing heart is made up of two tubes that join in the center, which creates a trunk with four tubes branching away to eventually form the heart and valves. The preliminary structures that make up the baby's heart begin spontaneously beating, and it is possible to detect with the help of vaginal ultrasound.
-
Week 6 - By this period, the baby's heart develops four hollow chambers, each with an entrance and an exit, to allow blood to flow in and out.
-
Week 12 - Circulatory development continues during this week when the baby's bone marrow begins to produce blood cells.
Second-Trimester Development
-
Week 17 - the fetus's brain begins to regulate the heartbeat in preparation for life in the outside world. Increased capillaries develop during the second trimester. These teeny-tiny blood vessels provide oxygenated blood to the tissues in the baby's body, and then deoxygenated blood is brought back into the circulatory system.
-
Between 18 and 24 Weeks - With the help of a fetal echocardiogram, better listening and view of the baby's heart is possible. The doctor can look at the structure of the baby's heart and check for any congenital heart defects.
Third-trimester Development
The baby's heart and circulatory system will continue to grow in a slow and steady phase during the last trimester so that by 40 weeks, the heart is completely ready to work outside the womb.
When Can a Fetal Heart Rate Not Heard Properly?
Certain factors may make fetal heart rate monitoring less accurate.
These include:
-
Polyhydramnios (too much amniotic fluid).
-
Obesity of the mother.
-
Position of the baby or mother.
-
When the amniotic sac is not broken.
-
When the cervix is not dilated.
Conclusion
Listening to the heartbeat of the baby is comforting to the parents. The heartbeat can be detected from six weeks of gestation and provides more information about the baby's health, so doctors check it during most prenatal check-ups.
