From the Guidelines
Loss of an X chromosome can indeed cause miscarriage, as approximately 99% of pregnancies with monosomy X end in spontaneous miscarriage, usually during the first trimester. This is due to the essential genes on the X chromosome that are necessary for fetal development, and the absence of a second sex chromosome disrupts normal embryonic growth. According to the study by 1, nearly all non-mosaic chromosomal abnormalities, including those involving the X chromosome, result in early miscarriage.
The high miscarriage rate associated with X chromosome loss can be attributed to the critical role of the genetic material on this chromosome in proper organ development and overall viability. While some fetuses with Turner syndrome, which is characterized by monosomy X, do survive to birth, they represent only a small percentage of conceptuses with this chromosomal pattern.
Key points to consider include:
- The severity of the impact of X chromosome loss depends on which specific genes are affected and at what developmental stage the chromosomal loss occurs
- Mosaicism, where the chromosomal abnormality is present in some but not all cells, can have a wide range of phenotypic consequences, as noted in the study by 1
- The incidence of mosaic chromosomal abnormalities, including those involving the X chromosome, is relatively rare, occurring in about 1% to 2% of pregnancies, according to 1.
In clinical practice, pretest counseling is critical in allowing individuals to make well-informed decisions about pursuing non-invasive prenatal screening (NIPS) or other diagnostic testing options, as recommended by 1. Consultation with a genetics healthcare professional would be prudent in any case when NIPS is being considered as an alternative to diagnostic testing.
From the Research
X Chromosome Loss and Miscarriage
- X chromosome loss, also known as 45,X, is a chromosomal abnormality that can occur in fetuses.
- According to a study published in 2021 2, 45,X was one of the most frequent chromosomal abnormalities detected in chorionic villus sampling (CVS).
- Another study from 2003 3 found that chromosomal abnormalities, including those affecting the X chromosome, were more common in couples with recurrent miscarriage.
- The study published in 2000 4 reported that numerical chromosomal abnormalities, which include X chromosome loss, account for about 50% of first-trimester pregnancy losses.
- While these studies suggest a link between X chromosome loss and miscarriage, the exact mechanisms and risks are not fully understood and may vary depending on individual circumstances.
Chromosomal Abnormalities and Miscarriage
- Chromosomal abnormalities are a well-documented cause of miscarriage, with numerical abnormalities being the most common type 4, 5.
- A study from 2008 5 highlighted the importance of considering gestational age and fetal development when studying miscarriage-associated factors.
- The role of genetic counseling and prenatal diagnosis, such as CVS and amniocentesis, in identifying chromosomal abnormalities and managing pregnancy risks is also crucial 6, 2.
- However, the relationship between X chromosome loss and miscarriage is complex and may involve various genetic and environmental factors.