Abdominal examination auscultation for fetal heart sounds

Although the fetal circulatory system begins to develop very early, the fetal heart sounds are heard under normal circumstances, usually until four and a half months after pregnancy.

The fetal heart sound is like the "drip" sound of the clock, the speed is very fast, about 120 to 160 times per minute, which is significantly faster than the adult heart rate, the rhythm is uniform, and it is easy to distinguish. If an electronic fetal tone amplifier is placed in the abdomen of a pregnant woman, the heart sounds of the fetus can be heard at the time of two months of pregnancy. If the fetal heart sound has not been heard for more than five months of pregnancy, care must be taken to observe whether the fetus is in a normal condition. Before the six months of pregnancy, the fetal heart sounds are mostly heard in the middle or left and right of the pregnant woman's lower umbilicus, and the fetal heart sounds after six months of pregnancy are generally heard most clearly in the position of the fetus's back. This suggests that listening to the fetal heart sounds, in addition to determining whether the fetal growth and development is normal, is helpful in diagnosing the fetal position. If more than two fetal heart sounds can be heard, combined with methods such as B ultrasound, it can be diagnosed whether it is a multiple pregnancy.

When listening to fetal heart sounds, you must learn to distinguish between several other sounds:

⊙ umbilical cord murmur. If the blood circulation of the fetal cord is blocked by some reason, it can cause a sound that resembles a blowing wind, that is, an umbilical cord murmur. It is a monophonic tone at the same rate as the fetal heartbeat, which is heard by about 15% of pregnant women.

⊙ uterine murmur. When blood flows through the enlarged uterine blood vessels, a wind-blowing sound of a low, powerful tone can occur. This uterine vascular murmur has the same rate as the pulse rate of pregnant women.

⊙ abdominal aortic sounds. Pregnant women's abdominal aorta can also produce a sound similar to the uterine vascular murmur, but this arterial vascular sound is like a drum "clucking" sound, and the rate is also the same as the maternal pulse.

⊙ fetal movement. When a fetal limb hits the uterine wall, it can cause a murmur that does not have a certain regularity, and the part is varied and sometimes absent.

Excerpt from "280 Days of Prenatal Education Every Day Reading", Hebei People's Publishing House, 2007, edited by Wang Xinliang

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