Info from : Baby's Heart Rate
The heart is one of the earliest
developing organs in a new baby, and hearing that tiny heartbeat is one
of the first pregnancy memories for many new parents. During pregnancy,
a baby's heart goes through many changes during development that affect
its size, function and rate.
Early Heart Formation
In
the rapidly growing fetus, the heart begins to beat at approximately 22
days after conception, often before the mother even realizes she is
pregnant. During this early stage of development, the heart grows from a
simple tube shape into a four-chambered beating heart. It is during
this period that the growing heart is at most risk for cardiac defects
and the baby is at highest risk for a miscarriage from those defects.
First Trimester
Shortly
after formation, the tiny heart has a beat that is similar to an
adult's heart rate, then it begins increasing at a few beats a week
through the ninth week. The heart first begins to beat at a rate of
about 80 beats per minute around five-weeks gestation, then steadily
increases to a mean of 175 bpm by the ninth week. The increase in fetal
heart rate at this point in the pregnancy is so steady that a study by
medical sonographers published a formula to help determine the fetal age
based on heart rate: Embryonic age in days = EHR(0.3)+6.
After that point, it begins to slow again throughout the pregnancy.
After that point, it begins to slow again throughout the pregnancy.
Gender Predictor?
Pregnancy
myth suggests that an unborn baby's heart rate can predict the baby's
gender, with faster heart rates (above 140 bpm) indicating a girl and
slower heart rates indicating a boy. The basis for this is the faster
metabolism of baby girls. There have been several studies, including a
large study by Austin Radiological Associates in the 1990s, but none has
shown a statistical correlation.
Second and Third Trimesters
Starting
at the end of the first trimester (around 10 weeks) the baby's heart
rate should be audible by a hand-held Doppler instrument. Prior to
this, the only way to confirm the heartbeat is by visualization on a
sonogram. With the Doppler instrument, the heartbeat will sound
surprisingly fast to most people, with an average rate of 120 to 160
bpm. New parents often describe the sound as similar to galloping
horses.
By 20 weeks of gestation, the baby's heart rate will be audible by a stethoscope or fetoscope, but this method can be more difficult if the placenta is attached to the anterior of the uterus or if the baby is positioned in such a way that her back is to the mother's back.
By 20 weeks of gestation, the baby's heart rate will be audible by a stethoscope or fetoscope, but this method can be more difficult if the placenta is attached to the anterior of the uterus or if the baby is positioned in such a way that her back is to the mother's back.
Labor and Delivery
Labor
and delivery are hard work for both mother and baby. The work that the
baby does to move into position and withstand uterine contractions is
evidenced by the normal fluctuations in heart rate that occur during
this time. Fetal heart rate can be monitored either externally or
internally, continuously or intermittently, during this time. A baby's
heart rate will normally accelerate during a contraction, then slow as
the mother and baby recover. If the baby's heart rate fails to recover
adequately, shows significant deviations from his normal baseline, or
does not respond to the work of the contraction, it could indicate a
problem that warrants medical attention.
0 comments:
Post a Comment