When does the fetal heartbeat and fetal bud appear in early pregnancy?

Fetal heart rate refers to the gradual formation of various organs during the development of the fertilized egg. It is formed at 30-40 days of pregnancy, the embryo bud is formed at 40-50 days, and the fetal heart is formed at 50-60 days. So there is only a dozen days in between, but it needs to develop slowly to have a complete little life. During this formation process, the body will also undergo some different changes, which we need to understand and recognize.

The embryonic bud and fetal heart refer to the first two weeks of the development of the fertilized egg, which is called the pregnant egg. Later, various organs gradually form. Before 8 weeks of pregnancy, it is called the embryo (or fetal bud); the third to first month and four weeks of pregnancy is called the fetal bud period.

As the embryo develops, the gestational sac is formed in 30-40 days, the fetal bud is formed in 40-50 days, and the fetal heart is formed in 50-60 days. Therefore, B-ultrasound should generally be done around 60 days. At this time, you can see whether the gestational sac, fetal bud, and fetal heart are normal.

Developmental process

Formation time

The period from the third trimester to the first month and four weeks of pregnancy is called the embryonic stage. The embryo is 0.5-1 cm long and shaped like a small seahorse.

Embryo size

4 weeks: The fetus is only 0.2 cm. The amniotic cavity is formed just after the fertilized egg has implanted and its volume is very small. Ultrasound cannot show clear signs of pregnancy.

5 weeks: The fetus grows to 0.4 cm and enters the embryonic period. The amniotic cavity expands and primitive cardiovascular system appears, which may beat. B-ultrasound can show a small gestational sac, which occupies less than 1/4 of the uterine cavity, or a fetal bud can be seen.

6 weeks: The fetus grows to 0.85 cm, and the head, brain alveoli, facial organs, respiratory, digestive, and nervous organs are differentiated. The fetal sac is clearly visible on B-ultrasound, and the fetal bud and fetal heartbeat are seen.

7 weeks: The fetus grows to 1.33 cm. The embryo has the rudiments of a human being. The body segments are fully differentiated, the limbs are separated, and all systems are further developed. B-ultrasound clearly shows the embryo and fetal heartbeat, and the gestational sac occupies about 1/3 of the uterine cavity.

8 weeks: The fetus grows to 1.66 cm. The fetal shape is determined, and the head, body and limbs can be distinguished. The head is larger than the trunk. B-ultrasound shows that the gestational sac occupies about 1/2 of the uterine cavity, the fetal shape and fetal movement are clearly visible, and the yolk sac can be seen.

9 weeks: The fetus grows to 2.15 cm, the head is larger than the body, the various parts are clearer, the skull begins to calcify, and the placenta begins to develop. B-ultrasound shows that the gestational sac almost fills the uterine cavity, the fetal outline is clearer, and the placenta begins to appear.

10 weeks: The fetus grows to 2.83 cm, all fetal organs have been formed, and the rudiments of the placenta are formed. B-ultrasound shows that the gestational sac begins to disappear, a crescent-shaped placenta is visible, and the fetus is active in the amniotic fluid.

11 weeks: The fetus grows to 3.62 cm, the fetal organs develop further, and the placenta develops. B-ultrasound showed that the gestational sac had completely disappeared and the placenta was clearly visible.

12 weeks: The fetus grows to 4.58 cm, the external genitalia begin to develop, any deformities will be revealed, and the calcification of the skull becomes more complete. The skull halo is clear, the biparietal diameter can be measured, obvious deformities can be diagnosed, and the internal organs tend to become more complete afterwards.

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Embryo characteristics

The first month of pregnancy is the embryonic stage, during which the new life grows the fastest in its life. The sperm and egg combine at the end of the second week of pregnancy. About 4 days after fertilization, the sperm and egg, which have split into cell clusters, travel along the fallopian tube to the uterus. In the third week, the cell mass sheds its outer membrane in preparation for implantation.

By the fourth week, the blastocyst has been firmly implanted in the uterus. During this period, the prototypes of the fetal nervous system and circulatory organs (the basic tissues) have almost appeared, and the liver begins to develop significantly from this period; the prototypes of the eyes and nose have not yet been generated, but the prototypes of the mouth and chin can be seen; the umbilical cord connected to the mother also begins to develop from this period.

Fetal heart rate

The fetal heart rate is the heartbeat of the fetus, which can usually be heard in the abdomen with a normal stethoscope between 17 and 20 weeks. The fetal heart rate is 120-160 beats/minute, sometimes even faster and less regular. It becomes more regular towards the end of pregnancy. Sometimes there may be a brief pause in the heartbeat, or the heart rate may reach 180 beats per minute, which is normal. However, if this phenomenon occurs frequently or for a long time, you should seek medical attention in time.

Normal range

The normal fetal heart rate is regular and strong, like the ticking of a clock, at 120-160 beats/minute. If it is <120 beats/minute or >160 beats/minute, you can listen to it again at intervals of 10-20 minutes. If it is still abnormal, it indicates fetal intrauterine hypoxia. If the fetal heart rate is within the abnormal range and is accompanied by irregular fetal heart rhythm, it indicates that the fetal hypoxia is more serious.