Chromosome findings in 2,500 second trimester amniocenteses

Area of Science:

• Medical Genetics
• Prenatal Diagnosis
• Cytogenetics

Background:

• Advanced maternal age (34+ years) is a significant risk factor for fetal chromosome abnormalities.
• Prenatal diagnosis through amniocentesis is a common procedure for assessing fetal genetic health.

Purpose of the Study:

• To analyze the types and prevalence of chromosome abnormalities detected via amniocentesis in a large cohort.
• To correlate the incidence of abnormalities with maternal age, particularly focusing on advanced maternal age.

Main Methods:

• Retrospective analysis of 2,500 amniocentesis cases performed for prenatal diagnosis.
• Categorization of chromosome abnormalities by type (e.g., Trisomy 21, sex chromosome abnormalities) and correlation with maternal age groups.

Main Results:

• Chromosome abnormalities were detected in 1.8% of cases referred due to advanced maternal age.
• The detection rate increased significantly with maternal age, reaching 4.6% in women aged 40 and over.
• Trisomy 21 was the most frequent abnormality (50%), followed by sex chromosome abnormalities (25%).
• Unexpected translocations were identified in 0.4% of cases.

Conclusions:

• Amniocentesis is an accurate (99.6%) diagnostic tool for identifying fetal chromosome abnormalities.
• Advanced maternal age remains a critical indicator for prenatal screening due to increased risk.
• Trisomy 21 and sex chromosome abnormalities are the predominant findings in this cohort.