SMFM: CMA Should Become the Standard for Prenatal Diagnosis

In a study of nearly 4,500 women, chromosonal microarray (CMA) was as effective at identifying aneuploidy as karyotyping. Lead study author Ronald Wapner, MD, of the National Institute of Child Health and Human Development’s Prenatal Microarray Study Group, concluded that CMA should become the new standard for routine and high-risk prenatal diagnosis.

To evaluate CMA as an independent method for prenatal diagnosis, villus or amniotic fluid samples were taken from 4,401 women at 31 centers and sent to a central karoytyping lab. Standard karyotyping was performed on half of the samples; the other half was de-identified and sent to one of four independent microarray labs for CMA. All women had indications of AMA (46%), abnormal ultrasound (26%), abnormal first or second trimester screening (18%), or other indication (9%).

Of the 4,340 samples available for comparison, 316 (7.3%) autosomal and 57 (1.3%) sex chromosome non-mosaic aneuploidies were identified by karyotype. CMA obtained successful results in 98.7% of cases. CMA identified anomalies in 100% of cases, however seven were reported as mosaic. All seven reported as mosaic originated from the same microarray lab.

The microarray also detected clinically relevant material in 2.5% of women with normal karyotypes.

Wapner noted that CMA did not detect triploidy, but in all cases, it was visible on ultrasonographic screening.

“The clinical goal is to use [CMA] in lieu of karyotyping. I’m not suggesting we run out and do it now; there needs to be a methodical, well thought out transition,” Wapner said, adding that the transition should establish guidelines for pre- and post-test counseling and what to do with unusual findings. 

Read our complete coverage of the Society of Maternal and Fetal Medicine's 32nd Annual Meeting, including:

SMFM: Progesterone Does Not Prolong Pregnancy After Successful Tocolytic Treatment

SMFM: Induction of Labor Reduces Trauma Risk for Large-for-Date Fetuses

SMFM: LEEP Does Not Increase Risk of Preterm Birth