Pap Smear Early in Pregnancy Could Reveal Genetic Disorders Earlier

A pregnant woman talks with her doctor.
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Prenatal screening for genetic disorders could be done as early as five weeks into a pregnancy with a simple Pap smear, according to a small new study.

Current methods for screening fetuses for genetic disorders are more invasive, and cannot be used until a woman is nine to 12 weeks pregnant, the researchers said. A Pap smear involves scrapping a small sample of cells from a woman's cervix.

The new findings suggest that Pap smears could one day help doctors diagnose and treat babies with genetic diseases, the researchers said in their study, published today (Nov. 2) in the journal Science Translational Medicine.

Genetic disorders that are caused by a certain gene, such as the blood disorders thalassemia and sickle cell anemia, are not common, but still "are a major health burden," the researchers wrote in their study. [7 Diseases You Can Learn About from a Genetic Test]

Being able to detect genetic disorders as early as possible is important because  doctors can then begin treating some of these disorders before birth, the researchers said.

For example, fetuses with a genetic disorder called congenital adrenal hyperplasia, which affects the functioning of adrenal glands and in some cases might be life-threatening, could be treated while the fetus is still in the womb, the researchers said. However, more research is needed to determine whether those treated in utero might have better outcomes than those who begin treatment after birth.

In the new study, the researchers tested the Pap smear method of prenatal testing in a group of 20 healthy women who were between five and 19 weeks pregnant. During the procedure, the researchers extracted cells from the placenta inside the mother's reproductive tract. Placental cells contain DNA material from the fetus. [Unraveling the Human Genome: 6 Molecular Milestones]

The researchers tested the cells and were able to identify and analyze detailed genomic profiles of the fetuses in the study. The study did not indicate whether any of the fetuses in the study turned out to have a genetic disorder.

The researchers did not report any adverse effects from the procedure.

One of the advantages of a Pap smear for prenatal testing is that it is less invasive than methods that are currently available, the researchers said. Those other methods involve direct sampling of the placenta or of the fluid that surrounds a developing fetus and that contains fetal tissues, the researchers said. Some of these procedures come with a small risk of fetal loss.

"If you can look at the whole genome as early as five weeks, it is kind of amazing," said Dr. Jennifer Wu, an OB-GYN at Lenox Hill Hospital in New York, who was not involved in the study.

However, the study was small and more research is needed to test this method of prenatal testing in a larger number of women, before it could be done regularly, Wu told Live Science.

Originally published on Live Science.

Staff Writer