The most common cause of first trimester spontaneous miscarriage is chromosomal abnormalities, accounting for approximately 50-70% of early pregnancy losses.
Chromosomal abnormalities
- The most frequent chromosomal abnormalities include trisomies, monosomy X (Turner syndrome), and polyploidy.
- Trisomy 16 is the most common specific trisomy associated with first trimester miscarriages.
- These abnormalities typically arise from errors during gametogenesis, such as nondisjunction during meiosis, leading to an abnormal number of chromosomes in the embryo.
- Chromosomal abnormalities were observed in 50.94% of cases in a study of Thai pregnant women, including 38.11% miscarriages and 12.83% intrauterine survivals
- In a Romanian cohort, chromosome abnormalities were detected in 58.7% of cases, with the most common type being single autosomal trisomy (52.6%), followed by monosomy (monosomy X being the only one detected, 17.8%), and polyploidy (17.0%)
Other causes
- Other less common causes of first trimester miscarriage include maternal factors such as uterine abnormalities (e.g., septate uterus, fibroids), endocrine disorders (e.g., uncontrolled diabetes mellitus, thyroid disease), infections (e.g., cytomegalovirus, toxoplasmosis), and thrombophilic disorders (e.g., antiphospholipid syndrome).
- Lifestyle factors such as smoking, excessive alcohol consumption, and illicit drug use can also contribute to the risk of miscarriage.
In conclusion, while there are several causes of first trimester spontaneous miscarriage, chromosomal abnormalities are the most common cause.