For the first time, researchers have determined virtually the entire genome of a fetus using only a blood sample from the pregnant woman and a saliva specimen from the father.

The accomplishment heralds an era in which parents might find it easier to know the complete DNA blueprint of a child months before it is born.

That would allow thousands of genetic diseases to be detected prenatally. But the ability to know so much about an unborn child is likely to raise serious ethical considerations as well. It could increase abortions for reasons that have little to do with medical issues and more to do with parental preferences for traits in children.

“It’s an extraordinary piece of technology, really quite remarkable,” said Peter Benn, professor of genetics and developmental biology at the University of Connecticut, who was not involved in the work. “What I see in this paper is a glance into the future.”