A surprising new study has found that a blood test that was intended to screen fetuses for genetic disorders like Down syndrome has instead successfully detected cancer in the mother that was previously unknown.

These “silent” cancers can be deadly, and the longer they remain undetected, the worse they get — meaning this new finding could be a boon to the medical community, according to a Boston Herald report.

The study was published by a team of researchers at Tufts Medical Center in the Journal of the American Medical Association. It analyzed eight cases where abnormal test results had nothing to do with fetal defects and everything to do with a malignant form of cancer in the woman’s body.

The Herald report cited one case of a 40-year-old woman who was informed of chromosomal problems found in her sample that seemed to indicate the baby had a low chance of survival, but the baby was fine — it was the mother who found out two months later after having problems with her shoulder and with breathing that she had non-Hodgkin’s lymphoma, a blood cancer.

The findings suggest that false positives on fetuses shouldn’t be thrown out, but should be taken as a possible sign that the mother herself needs closer examination.

The findings were “very unexpected,” according to Dr. Diana Bianchi, who is the lead researcher and the executive director of the Mother Infant Research Institute at Tufts, as quoted in the report. It may suggest that this test is just as important for the mom as it is the child.

The medical community has been using this test since 2011. It is typically a non-invasive first step that can lead to more invasive procedures to confirm positive results, such as sampling bodily fluids.