WASHINGTON – It’s one of the biggest purchases for soon-to-be parents: a crib for baby. Beginning today, a new generation of cribs, designed to be safer, will be the only ones approved for sale – in stores, online, and even at neighborhood yard sales.

Ushering in one of the most significant changes in child safety in decades, the rules ban the manufacture, sale and resale of drop-side cribs. Drop-sides have a side rail that can be raised and lowered to allow parents to more easily place or lift a baby, but they have been blamed in the deaths of several dozen children.

Another significant part of the new federal standard mandates more rigorous safety tests for children’s cribs before they hit the market. In the past, manufacturers were allowed to retighten screws and bolts on a crib during hardware testing meant to mimic how a child might rattle a crib – by jumping up and down or shaking a rail.

While the tests were intended to simulate a toddler in a crib, they don’t mimic the reality of the parent. It’s a rare parent who would know when to retighten obscure pieces of hardware on a crib during normal use by a child.

The retightening of screws and bolts during durability tests on cribs ends today, as part of the new rule approved last year by the Consumer Product Safety Commission. Stronger mattress support systems and crib slats are also a major part of the new testing.

“After 30 years of having outdated standards, CPSC delivered on its promise and created the toughest crib safety standards in the world,” commission Chairman Inez Tenenbaum told the Associated Press. “Parents can now shop for a crib with confidence.”

New cribs on the market won’t really look different other than the obvious absence of a movable side that drops down. Now, all four sides will be fixed and the cribs should be sturdier because of the tougher testing requirements.

Drop-side cribs have been around for decades. But they have increasingly come under scrutiny in recent years because of malfunctioning hardware, sometimes cheaper plastics, or assembly problems that can lead to the drop-side rail partially detaching. That can create a dangerous “V”-like gap with the mattress in which a baby can get caught and suffocate.

Drop-sides are blamed in the deaths of more than 30 infants and toddlers since 2000 and suspected in about a dozen other infant fatalities. Since 2007, more than 9 million drop-sides have been recalled including cribs from Evenflo and Pottery Barn Kids.

While drop-side cribs will no longer be made or sold, they are still being used in homes across the nation. The industry says drop-sides that haven’t been recalled can be used safely as long as they are properly assembled and maintained to the manufacturer’s instructions. Manufacturers do not recommend using cribs that are more than 10 years old.