The American College of Obstetricians and Gynecologists (The College) and the Society for Maternal-Fetal Medicine (SMFM) have recommended Chromosomal Microarray Analysis (CMA) as the first-line genetic test in pregnancies showing fetal abnormalities in an ultrasound scan.
CMA is capable of detecting smaller genetic anomalies which are not detected by standard Karyotyping analysis. Moreover, CMA is a computerized test and hence more reliable as compared to Karyotyping which is dependent on manual process and skills.Recommendations
The College and the Society for Maternal-Fetal Medicine offer the following recommendations for the use of chromosomal microarray analysis in prenatal diagnosis.
- In patients with a fetus with one or more major structural abnormalities identified on ultrasonographic examination and who are undergoing invasive prenatal diagnosis, chromosomal microarray analysis is recommended. This test replaces the need for fetal karyotype.
- In patients with a structurally normal fetus undergoing invasive prenatal diagnostic testing, either fetal karyotyping or a chromosomal microarray analysis can be performed.
- Most genetic mutations identified by chromosomal microarray analysis are not associated with increasing maternal age; therefore, the use of this test for prenatal diagnosis should not be restricted to women aged 35 years and older.
- In cases of intrauterine fetal demise or stillbirth when further cytogenetic analysis is desired, chromosomal microarray analysis on fetal tissue (ie, amniotic fluid, placenta, or products of conception) is recommended because of its increased likelihood of obtaining results and improved detection of causative abnormalities.
- Limited data are available on the clinical utility of chromosomal microarray analysis to evaluate first-trimester and second-trimester pregnancy losses; therefore, this is not recommended at this time.
- Comprehensive patient pretest and posttest genetic counseling from qualified personnel such as a genetic counselor or geneticist regarding the benefits, limitations, and results of chromosomal microarray analysis is essential. Chromosomal microarray analysis should not be ordered without informed consent, which should be documented in the medical record and include discussion of the potential to identify findings of uncertain significance, nonpaternity, consanguinity, and adult-onset disease.
Committee Opinion #581 “The Use of Chromosomal Microarray Analysis in Prenatal Diagnosis” is published in the December issue of Obstetrics & Gynecology.