UNC team issues guide for screening patients when prenatal testing suggests maternal illness

Though the finding is rare, it is possible. Dr. Laura Carlson's team established a protocol to help other obstetricians.

Dr. Laura Carlson and a team of obstetrician-gynecologists and oncologists have developed an algorithm for how to evaluate a pregnant woman for cancer when prenatal genetic testing reveals a problem not with her fetus' health, but with hers.

Carlson and her team published commentary in the March 2018 issue of Obstetrics & Gynecology to provide a guide for maternal-fetal medicine specialists and oncologists who might encounter this rare event among their own patients.

Carlson herself had a pregnant patient at UNC Maternal-Fetal Medicine whose prenatal genetic testing revealed her own malignancy.

"We weren't sure how exactly to evaluate this woman for cancer," said Carlson. "We started looking into the literature, and there wasn't anything out there."

Cell-free DNA screening, a noninvasive genetic screening test, analyzes fragments of placental and maternal DNA that circulate in maternal blood to report information about possible chromosomal abnormalities in fetuses. Because the mother's DNA is involved, maternal health conditions, such as maternal malignancy, may be identified.

In the case of Carlson's patient, further genetic screening did not indicate fetal abnormalities. They suspected the testing detected an abnormality in the mother's DNA instead. Carlson and her team discussed the most common cancers in pregnancy and in patients with malignancy previously identified by cell-free DNA screening, and how to evaluate for these cancers.

The patient's malignancy was identified using the algorithm developed by Carlson and her team, and was subsequently referred to oncology for further management. The algorithm is simple and noninvasive, involving a full history and physician exam, straightforward lab testing, and imaging if prior testing is unrevealing.

The commentary refers to a 2015 study, in which 3,757 samples from a cohort of 125,426 cell-free DNA results were positive for aneuploidy, or abnormal number of chromosomes. Of these cases, 10 detected a maternal malignancy. Of patients with more than one aneuploidy detected, 18 percent translated to a maternal malignancy.

As maternal age and uptake of cell-free DNA screening increase, it is likely that providers could see more of these cases, said Carlson. The group decided to publish the commentary as a way to guide other providers should they encounter maternal illness revealed by these screening tests.

Carlson encourages any patients undergoing prenatal genetic testing do so only after thorough counseling. "More and more low risk woman are getting these tests as a way to find out the gender earlier," she said. "But the test is designed to look for chromosomal abnormalities in a fetus, and sometimes the results that come back can tell you things you didn't expect to find out. Without a genetics professional to guide you, it can cause a lot of stress."

Other UNC School of Medicine faculty who contributed to the commentary are Emily Hardisty and Dr. Neeta Vora from the Division of Maternal-Fetal Medicine and Dr. Catherine Coombs in the Division of Hematology/Oncology. Coombs is also a member of the UNC Lineberger Comprehensive Cancer Center at UNC-Chapel Hill.

Read the commentary

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