1. Chromosome quantitative abnormalities: common types and risks

Chromosomequantitative abnormalities fall into two categories:
·Aneuploidy abnormalities: such as trisomy 21 (Down's syndrome), trisomy 18, Turner's syndrome (X monomer), etc., account for 50%-60% of IVF abortions.
· Abnormalities related to whole chromosome pairs: Such as trisomies (69 chromosomes) or polyploidy, usually result in embryos being unable to survive.
Research indicates that older women (aged 35 and above) have a significantly increased risk of chromosomal abnormalities during egg formation. In addition, male age (>40 years old) may also affect chromosomal distribution indirectly, through an increase in sperm DNA fragmentation.
The second and four core causes: from meiosis to environmental interference

.1. Meiotic error: a "misallocation" during egg or sperm formation
Eggaging: Female oocytes are stored at birth. As they age, chromosome "subpackaging" during meiosis is prone to errors (such as chromosome 21 not being evenly divided), resulting in one more or one less chromosome in the gamete.
Abnormal sperm: When the sperm DNA fragmentation rate exceeds 30%, the risk of chromosomal abnormalities increases significantly. This may affect the chromosomal distribution of embryos after fertilization.
2. The "replication accident" of fertilization and early division
Even if the initial chromosomes of a fertilized egg are normal, mitotic errors during cell division after fertilization may lead to abnormal chromosome numbers in some embryonic cells (such as amputation).
3. "Hidden interference" between environment and genetics
·Environmental factors: Radiation, chemical poisons (such as formaldehyde, pesticides), and viral infections (such as rubella virus) may disrupt the chromosomal stability of meiosis or early embryos.
·Genetic susceptibility: If parents have chromosomal balanced translocations or inversions (structural abnormalities), even though they themselves appear to be normal, they may still produce gametes with chromosomal imbalances, thereby increasing the rate of embryonic abnormalities.
4. Influence of laboratory culture conditions
Duringthe in vitro culture of IVF babies, fluctuations in the composition, temperature or pH value of the culture medium may interfere with the division of embryonic cells, but existing technology has greatly reduced such risks.
3. Coping strategies: How to reduce abnormal risks?
III. Strategies for dealing with risks: How to reduce abnormal risks?

·Scientific preparation for pregnancy: Women are advised to complete childbearing before 35; men need to improve their lifestyles (quit smoking and alcohol, avoid high temperatures).
·Third-generation IVF technology (PGT-A): This technique involves pre-implantation chromosome screening of embryos, allowing for the selection of healthy embryos for transfer.
·Pre-pregnancy examinations include chromosomal analysis for both spouses, sperm DNA fragmentation testing, and management of chronic diseases (such as thyroid function issues).
·Environmental protection: Avoid exposure to radiation and chemical toxins. During the preconception period, it is recommended to take folic acid to reduce the risk of neural tube defects.
Chromosomal abnormalities are mostly random events, and there is no need to be overly anxious about a miscarriage.
,.Through third-generation IVF technology and strict pre-pregnancy management, the probability of healthy pregnancies can be significantly improved.