Background:
Prenatal diagnosis is an important part of obstetric care and is aimed at identifying potential genetic abnormalities in fetuses. Chromosomal microarray analysis (CMA) is becoming the preferred diagnostic method due to its higher resolution than traditional cytogenetics.

Objective:
This study aimed to determine the prevalence of major and sub-chromosomal abnormalities in fetuses with ultrasound findings during routine anatomy scans or pregnancies of advanced maternal age after maternal request without medical indication.

Methods:
A total of 126 cases were included in the study, divided into two groups: 84 fetuses with isolated sonographic soft markers and 42 fetuses from mothers of advanced maternal age. The group of isolated sonographic markers was further categorized by the affected anatomical system. Both QF-PCR and CMA were used to detect genetic aberrations.

Results:
Clinically significant genetic abnormalities were found in 12% of the first group and 7% of the second group. Interestingly, 40% and 67% of the abnormal cases in the first and second groups respectively were only detected with CMA, while they would have been missed by standard karyotype or QF-PCR alone. The most common genetic aberrations were detected in fetuses with findings in the central nervous, craniofacial, cardiovascular, and musculoskeletal systems. CMA also identified sub-microscopic chromosomal aberrations in cases with short long bones and one case with ventriculomegaly.

Conclusion:
This study highlights the importance of using CMA for prenatal diagnosis, even in low-risk pregnancies with isolated sonographic markers or advanced maternal age. It can help identify clinically significant genetic abnormalities that may have been missed with traditional cytogenetics, leading to better clinical management and counseling.