What is the probability of fetal arrest after the presence of fetal heartbeat?

There is no definite value for the probability of fetal arrest after the presence of fetal heartbeat. There are usually many reasons that may cause fetal arrest, such as endocrine disorders, progesterone and estrogen are not in a balanced state, which is not conducive to the development of the embryo, and uterine abnormalities and chromosomal problems may also cause fetal arrest.

1. Endocrine disorders

Embryo implantation and continued development depend on the coordination of a complex endocrine system. Any abnormality in any link can lead to miscarriage. During the early development of the embryo, three important hormone levels are required: estrogen, progesterone, and human chorionic gonadotropin. As for the mother, if her own endogenous hormones are insufficient, it cannot meet the needs of the embryo and may cause embryo arrest and miscarriage. The most common of these is luteal dysfunction, which can cause delayed endometrial development and a short luteal phase, thereby affecting the implantation of the fertilized egg or early pregnancy miscarriage. People with luteal insufficiency are often accompanied by other glandular dysfunctions, such as hyperthyroidism or hypothyroidism, diabetes, relative androgenism and hyperprolactinemia. These factors are not conducive to embryonic development and are closely related to miscarriage.

2. Uterine abnormalities

Both the internal environment of the uterus and the overall environment of the uterus may have an impact on the embryo. The internal environment is the endometrium. If it is too thin or too thick, it will affect implantation. About 10% to 15% of miscarriages are caused by uterine defects. Common ones include (1) congenital abnormalities of the Müllerian duct, including unicornuate uterus, didelphic uterus, septate uterus, and bicornuate uterus, which result in a narrow uterine cavity and restricted blood supply. Abnormal development of the uterine arteries can lead to asynchrony of decidualization and abnormal implantation. (2) Intrauterine adhesions, which are mainly caused by intrauterine trauma, infection or residual placental tissue, leading to intrauterine adhesions and fibrosis. Hinders normal decidualization and placental implantation. (3) Uterine fibroids and endometriosis cause reduced blood supply, leading to ischemia and venous dilatation, asynchronous decidualization, abnormal implantation, and hormonal changes caused by fibroids, which can also cause pregnancy failure. (4) Congenital or traumatic cervical relaxation and abnormal cervical development caused by intrauterine treatment with diethylstilbestrol often lead to mid-term miscarriage.

3. Chromosome problems

If the chromosomes are abnormal, it may cause the embryo to not develop and lead to early miscarriage. Chromosomal abnormalities include quantitative and structural abnormalities. Quantitative abnormalities can be divided into aneuploidy and polyploidy. The most common abnormal karyotype is aneuploid trisomy, and trisomy 16 accounts for 1/3 and is often lethal. 25-67% of pregnancies with trisomy 21, 4-50% of pregnancies with trisomy 13, and 6-33% of pregnancies with trisomy 18 are bound to result in miscarriage. Others include haploid (45, XO) and tetraploid, which result in embryonic underdevelopment due to abnormal cleavage. Structural abnormalities include deletions, balanced translocations, inversions, overlaps, etc.