The young couple, shy and flush with excitement about her first pregnancy, sit down with Daniela Iacoboni, a prenatal genetic counselor at North Central Bronx Hospital. They are from Mexico and speak no English.

“Do you know why you’re here today?” Ms. Iacoboni asks in Spanish.

They do not.

“The results from your blood test showed positive for Down syndrome,” Ms. Iacoboni says.

No response.

Ms. Iacoboni asks them whether they know about chromosomes.

They do not.

But her job is made even more grueling because the women referred to her are overwhelmingly minority, poor and poorly educated. Their first languages might be Albanian, Bengali, Urdu, Korean or Wolof.

Some do not have partners. Earlier this morning, a 37-year-old patient who spoke only Mandingo sat with her head bowed, as her husband declared that because his other children were born healthy, there was no need to test this one. One patient is homeless; another became pregnant and HIV-positive after she was raped.