Chromosome analysis of 303 pregnancy losses in Mexico.

Background: Chromosomal abnormalities are present in 50 to 60% of miscarriages and in 6 to 19% of stillbirths. Although microarrays are preferred for studying chromosomal abnormalities, many hospitals cannot offer this methodology.

Objective: To present the results of the cytogenetic analysis of 303 products of conception (POC), which included 184 miscarriages, 49 stillbirths and 17 cases of undefined age.

Frequent copy number variants in a cohort of Mexican-Mestizo individuals.

Background: The human genome presents variation at distinct levels, copy number variants (CNVs) are DNA segments of variable lengths that range from several base pairs to megabases and are present at a variable number of copies in human genomes. Common CNVs have no apparent influence on the phenotype; however, some rare CNVs have been associated with phenotypic traits, depending on their size and gene content. CNVs are detected by microarrays of different densities and are generally visualized, and their frequencies analysed using the HapMap as default reference population.

Detection of mosaicism in lymphocytes of parents of free trisomy 21 offspring.

Down syndrome (DS) resulting from free trisomy 21 (FT21) has been largely associated with advanced maternal age. However, approximately 60% of FT21 cases are born to young couples. Thus, the etiological factors responsible for these FT21 children must differ from those proposed for maternal age-related FT21.