Generalized abnormal embryonic development in missed abortion: embryoscopic and cytogenetic findings.

A direct view of the embryo by means of transcervical embryoscopy prior to evacuation in 154 cases of missed abortion showed general embryonic maldevelopment in 48 cases (31%). A successful cytogenetic evaluation of these growth-disorganized embryos was performed in 37. Chromosomal abnormalities were found in 26 cases (70%), with autosomal trisomies in 24 cases (92%). Trisomies involved chromosome 3 (one case), 6 (one case), 8 (two cases), 10 (one case), 12 (two cases), 14 (one case), 16 (11 cases), 20 (one case), and 22 (four cases). Most of these chromosome abnormalities represented nonviable defects, and their presence explained the minimal embryonic development observed embryoscopically. An apparently normal karyotype was observed in 11 growth-disorganized embryos whose maldevelopment was similar to that resulting from the trisomies listed above. The factors responsible for embryonic maldevelopment with a normal karyotype are presently unknown and require further study, including investigation of imprinting defects, subtelomeric abnormalities, and cryptic mosaicism.