The hallway in the long, narrow apartment in Washington Heights is kept dark most of the time, to save on energy bills. In one bedroom, damp laundry hangs from the railing of a canopy bed, a neat rectangle of blue baby blankets and teddy-bear-dotted clothes, all belonging to 8-month-old Kyler Barr, who is sleeping soundly in the next room.

“Since he’s a preemie, I don’t want to use the washing machines at the laundromat,” said his mother, Tysheen Barr, with a self-deprecating chuckle. “I’m paranoid. But there might be germs left in there that aren’t good for him.”

It was Ms. Barr’s troubled pregnancy with Kyler that took her from steadily employed to jobless and temporarily homeless. Early this year, she was working in food service at a public elementary school, while taking care of her other son, Kysheen, whose ninth birthday is Monday.

But halfway through her pregnancy, it became clear that something was terribly wrong. Sonograms indicated that the baby was much smaller than he should have been. The doctors briefly worried that he had Down syndrome.