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The U.S. Food and Drug Administration is recommending parents stay away from 3D "keepsake ultrasounds," which do not serve a medical purpose.

The FDA issued a revised consumer update on Tuesday, saying it "strongly discourages" ultrasound imaging for the sake of just seeing what the fetus looks like. "While FDA recognizes that fetal imaging can promote bonding between the parents and the unborn baby, such opportunities are routinely provided during prenatal care," the agency said.

There is no evidence that ultrasounds cause harm, Today.com reports, but ultrasounds can slightly heat human tissue and produce "very small bubbles in some tissues," FDA biomedical engineer Shahram Vaezy said in a statement.