What is the reason for having yolk sac but no germ?

It is very important to have relevant checkups during pregnancy for the fetus. When we check in early pregnancy and find that there is a yolk sac but no embryo, we must be very worried. Doctors usually recommend a follow-up checkup after a while, as pregnant women must be very depressed during this period. Therefore, it is necessary for pregnant women to understand the reasons for having a yolk sac but no germ. So what is the situation with having yolk sac but no germ? Please see the detailed introduction below.

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. If an ultrasound examination is performed during this period and a yolk sac is found but no germ, what is going on?

1. The pregnancy time is too short and the embryo has not yet formed. After a follow-up examination after a period of time, most people will be able to detect the embryo, so there is no need to worry too much.

2. Abnormal embryonic development is the most common cause of early miscarriage, and miscarriage caused by chromosomal abnormalities accounts for about 50-60%.

3. Placental abnormalities: due to incomplete development of the trophoblast, degeneration of the placental villi, or the placenta being attached too low, fetal-placental circulation may be impaired, leading to miscarriage.

4. Acute infectious diseases may cause fetal death due to the invasion of pathogens or toxins through the placenta.

5. Severe anemia or heart failure may cause fetal death due to lack of oxygen.

6. Endocrine disorders, such as corpus luteum insufficiency, lead to decidua hypoplasia and affect the development of fertilized eggs.

7. Uterine hypoplasia, uterine fibroids or deformities can also hinder embryonic development.

8. Exposure to toxic substances such as cadmium, lead, organic mercury, DDT and other radioactive substances. These toxic substances may act directly on the fetal somatic cells or may affect the fetus through the placenta and cause miscarriage.

9. After the mother becomes pregnant, the immune system of both mother and child is not compatible, which causes the mother to reject the fetus and lead to miscarriage. The relevant immune factors that have been discovered include the spouse's tissue compatibility antigens, fetal antigens, blood type antigens, imbalance in maternal cellular immune regulation, maternal blocking antibodies during pregnancy, and lack of maternal cytotoxic antibodies against paternal lymphocytes.

The above is the introduction about what happens when there is a yolk sac but no germ. If a pregnant woman finds herself in this situation, it is recommended to wait a week before checking again. If the re-examination results are still the same, there may be a problem with the embryo, and you need to consult an obstetrician and gynecologist.