Prenatal screening is an important part of any pregnancy. Typically, noninvasive techniques, such as examining Fetal Cells in Maternal Blood (FCMB), ultrasound, or nonstress tests are used to screen for a prenatal condition. Fetal karyotype testing, which detects major chromosomal mutations, is commonly used as a confirmatory test after abnormalities are detected through screening. Chromosomal microarray is another, relatively newer procedure, used in prenatal diagnosis of chromosomal abnormalities. It has been shown to be able to detect more genetic mutations in children compared to regular karyotyping, leading some to think it should be a first-line confirmatory test over karyotyping.

Now, a prospective cohort trial of over 4400 women recently published in the New England Journal of Medicine shows that microarray analyses are equally efficacious as karyotyping in identifying certain chromosomal abnormalities (aneuploidies and unbalanced rearrangements) and may provide additional structural chromosomal findings in patients with normal karyotypes. Microarray testing in fact identified important genetic anomalies missed by karyotyping in nearly 2% of pregnancies with the usual indications for diagnostic testing (such as advanced maternal age) and 6% of cases with abnormal ultrasounds.

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