Chromosomes and Miscarriage

50 to 80% of first trimester losses are caused by chromosomal abnormalities

The earlier the pregnancy loss occurs, the greater the likelihood of genetic causation. Among first trimester miscarriages, 50% to 80% show chromosomal abnormalities, usually aneuploidy. This is greater than all other causes combined. Chromosomal numerical abnormalities can be recurrent and sporadic; failure to take this into account is a major pitfall in many reports addressing causation. Moreover, many causes of fetal wastage that are traditionally considered to be "nongenetic" are actually the result of perturbations of gene products-proteins.

http://www.ncbi.nlm.nih.gov/pubmed/17304022

Aneuploidy is found in 59% of miscarriages

A total of 204 miscarriages were included, from women with a mean age of 34.5 years. The overall rate of aneuploidy was 59%.

http://www.ncbi.nlm.nih.gov/pubmed/20190263

2 to 4% of recurrent miscarriages are caused by genetic abnormalites

Between 0.5 and 1.0% of couples experience recurrent miscarriage, which is defined as three or more consecutive miscarriages. Genetic abnormalities are responsible for recurrent miscarriage in 2-4% of these couples.

http://www.ncbi.nlm.nih.gov/pubmed/15749068

Chromosomal abnormalities less common in recurrent miscarriage

Among 59 samples from first miscarriage we found 25 abnormal karyotypes (42%). In the 61 samples from the second, third and the next miscarriages we found 20 chromosomal abnormalities (33%). CONCLUSIONS: Frequency of chromosomal aberrations in the tissue from the first miscarriage is significantly higher than in samples from second or following miscarriages, which means that genetic factors are less likely to induce recurrent miscarriages. Genetic results confirm that most chromosomal abnormalities arise de-novo.

http://www.ncbi.nlm.nih.gov/pubmed/21395079

In couples with recurrent miscarriage, 8% of females, 5% of males found to have abnormal karotype

This study determined the frequency of chromosomal aberrations in a series of couples with two or more miscarriages. Methods : This was a descriptive study conducted on 100 couples with recurrent miscarriage. Both partners were karyotyped as part of the primary investigation. Other probable causes of miscarriage were also investigated. Results : Chromosomal aberrations were found in 8 (8%) of the females and 5 (5%) of the males. The prevalence of chromosomal abnormalities was as follows: 4 (30.8%) balanced reciprocal translocations, 3 (23%) Robertsonian translocations, 3 (23%) pericentric inversions, 1 (7.7%) paracentric inversion, 1 (7.7%) chromosomal marker, and 1 (7.7%) polymorphism 9qh+.