A Pap smear can scoop up fetal cells for genome testing

Scanning a fetus’s genome just a few weeks after conception may soon be an option for expecting parents. Mom just needs to get a Pap smear first.

By scraping a woman’s cervix as early as five weeks into a pregnancy, researchers can collect enough fetal cells to test for abnormalities linked to more than 6,000 genetic disorders, researchers report November 2 in Science Translational Medicine. It’s not clear exactly how fetal cells make their way down to the cervix, says study coauthor Sascha Drewlo of Wayne State University School of Medicine in Detroit. But the cells may invade mom’s mucus-secreting glands, and then get washed into the cervical canal.

Current prenatal tests include amniocentesis and chorionic villus sampling, but they work later in pregnancy: at least 12 weeks for amnio and at least nine weeks for CVS. Amnio requires a long needle threaded through a pregnant woman’s belly and uterus; CVS often does, too. Instead, Drewlo’s team gathered fetal trophoblast cells, which give rise to the placenta, and were able to examine the genomes of 20 fetuses.

The new technique, which can work with as few as 125 fetal cells, could one day help physicians care for their tiniest patients. For some genetic conditions, such as congenital adrenal hyperplasia, early detection means mom can take some medicine to “actually treat the fetus in utero,” Drewlo says.