"Your baby is in trouble and there's no pulse. What do you do?"

It's the kind of question any parent would rather never consider. The thought of one's baby not breathing, choking or being unconscious is terrifying, yet on a recent evening, nine mothers and three fathers, a grandmother and two care givers met for four hours at a Glover Park home to learn exactly how they might save their child in a life-threatening emergency.

"Never, never turn your back on any baby near water," the stocky man barks at the group. From the first intense minute on, Noel Merenstein is no-nonsense. He demands no distractions, no note taking, no talking. His message rings of do-it-or-else ... or else some day you may be sorry.

When he was an emergency medical technician in New York City before starting his Baby-Life classes, Merenstein saw too many of those tragedies. He doesn't spare his classes the details:

"A mother in New York turned away from her child in the bathtub just long enough to get a dry towel," he says. "In a second the child slipped under the water and stopped breathing. The mother didn't know what to do. The child died ... "

An East Side father tried to remove a wad of paper with his fingers from his infant son's mouth and instead shoved it down farther. He tried slapping the child on the back, which lodged it tighter. "The child died in his father's arms on the way to the hospital," says Merenstein, warning that wrong action can be as bad as inaction.

"So many of these tragedies could be prevented in the first place -- but so much of it is not common sense," says Merenstein, 41, who began offering Baby-Life classes in Baltimore and Washington a year ago. "Parents are depending on others to keep their child safe when, really, it is their job."

One of the mothers there, Kim Foley, decided to sponsor the class in her home after she saw a TV report about Baby-Life. "What if my child were to fall down the steps and was hurt? I wouldn't know what to do," says Foley, 33, explaining why she wanted to take the course and learn CPR, the Heimlich maneuver and other techniques for infants and kids.

In the past five years, almost 50,000 people have taken Baby-Life classes for the same reason. Merenstein calls Baby-Life "a kind of combat training" for parents. "We make parents combat-ready," says the former Marine, who structures the course dynamics after military training. If that style is high-pressured compared to other classes, so is its subject. This is bottom-line parenting. At issue is life and death.

Those in the room grasp the rubber dolls they've been handed. Merenstein yells at them, "Your baby is in trouble. What do you do?" Some hesitate. All concentrate and react. They poke their dolls, call out "Baby! Baby!"

Merenstein shouts, "Is your baby breathing?" They lean close to the dolls as if to listen. Immediately, they begin to repeat the step-by-step procedures they'd been practicing. "You think this is pressure?" Merenstein asks the group. "This is nothing compared to what you'll be feeling if, God forbid, something should happen to your baby."

In the final two hours, Merenstein covers choking and runs down a list of foods and objects proven dangerous to children. "Balloons are the No. 1 hazard -- kids choke on them," he says. "No hotdogs or grapes before the 2-year molars come in. No peanuts or popcorn until age 5 ... A finger full of peanut butter? Kids choke on it. Even the Heimlich won't get out peanut butter."

By the end of the evening, everyone looks drained. "These guys really make you nervous" about your child's safety, says Susan Carroll, 29, a mother of a 4-month-old. Susan Engles, 31 and a mother of two, had been skeptical about the Baby-Life fee -- $45 a person, including a refresher class. Afterward, she said it was unlike any CPR or parent-education class she'd ever taken. "The pressure was on but they took the time to make everyone do it," says Engles, anxious to get home and check on her children.

"As scary as the class is," says Merenstein, "it gives parents the tools that may enable them to save their child's life. What we're aiming for is to open people's eyes enough that it'll never have to happen in the first place."

For Baby-Life scheduling and information: (212) 744-0805.