Mosaicism in chorionic villus sampling: an association with poor perinatal outcome

Area of Science:

• Prenatal diagnosis
• Cytogenetics
• Reproductive medicine

Background:

• First-trimester chorionic villus sampling (CVS) is a key method for prenatal diagnosis.
• Chromosomal abnormalities detected via CVS require accurate interpretation to guide clinical management.
• Understanding the implications of mosaicism found in placental tissue is crucial for fetal assessment.

Purpose of the Study:

• To evaluate the incidence of chromosomal mosaicism detected through chorionic villus sampling.
• To determine the correlation between placental mosaicism and fetal chromosomal constitution.
• To assess the impact of placental mosaicism on perinatal loss rates.

Main Methods:

• Conducted prenatal diagnosis using first-trimester chorionic villus sampling in 4319 pregnancies (4395 fetuses).
• Obtained cytogenetic information using rapid cytotrophoblastic preparation and monolayer mesenchymal tissue culture.
• Analyzed chromosomal constitution in both placental cytotrophoblast and fetal mesenchymal core samples.

Main Results:

• Chromosomal mosaicism was identified in 55 of 4319 pregnancies (1.3%).
• Abnormal cell lines were predominantly found in the cytotrophoblast (79.6% of mosaic cases).
• Placental mosaicism was associated with a significantly higher perinatal loss rate (16.7%) compared to non-mosaic cases (2.7%).

Conclusions:

• Cells from the mesenchymal core more accurately reflect the fetus's chromosomal constitution than cytotrophoblast cells.
• Placental mosaicism detected by CVS, even when the fetus is chromosomally normal, is linked to increased perinatal loss.
• Placental mosaicism may represent an independent risk factor for adverse perinatal outcomes.