Best crib mattresses

A crib mattress is made to go in your baby's crib. Choosing a safe and supportive crib mattress is important, because your baby may sleep on it for three years or more. When it comes to babies, the firmer the mattress, the better. Even if it feels stiff to you, your baby will adjust to it. A too-soft mattress raises your baby's risk for suffocation and sudden infant death syndrome (SIDS).

The Consumer Product Safety Commission (CPSC) requires that full-size crib mattresses be at least 27 1/4 inches wide by 51 1/4 inches long, with a thickness not exceeding 6 inches.

A crib mattress needs to fit snugly in the crib to prevent suffocation or entrapment. There should be almost no space between the side of the mattress and the crib frame. An easy way to check whether your mattress is safe: Make sure you can't measure more than two fingers width (1 inch) between the edge of the mattress and the crib frame.

The CPSC doesn't regulate the size of mini crib mattresses, but the standard size for these is 24 inches wide and 38 inches long.

Here are some things to consider when buying a crib mattress:

Firmness: The firmer the crib mattress the better (mattresses designed for older children and adults may not be firm enough).

Density: You want high density so it's firm enough to keep your baby safe while sleeping.

Resiliency: When you push your hand down into the middle of the mattress and remove it, how quickly does it regain its shape? Faster is better; sleeping babies make an impression on the foam, and it can be difficult for them to change position if the mattress retains their shape.

Weight: A typical foam mattress weighs about 7 to 8 pounds, although mattresses made of memory foam (an especially dense form of polyurethane) can weigh close to 20 pounds. Innerspring crib mattresses are heavier in general, weighing in at about 15 to 25 pounds. Keep in mind that you'll be hoisting up a side of the mattress, or lifting the whole thing, when changing your baby's crib sheet.

A waterproof cover: Many mattresses have covers advertised as waterproof, but they may not be able to repel major spills or diaper overflow. Consider using a fitted, waterproof mattress cover under the crib sheet.

Cleaning: Most crib mattresses are spot-cleaning only. Some have removable covers that can be machine washed.

Certification seals: For organic mattresses, look for an Oeko-Tex Standard 100 certification, a worldwide uniform certification. The GREENGUARD Gold certification means the mattress has low chemical emissions and is tested for more than 10,000 individual volatile organic compounds. CertiPUR-US certification means that a foam mattress doesn't contain toxic chemicals or flame retardants, and has low chemical emissions.

Note: No matter what crib mattress you choose, make sure to follow safe sleep guidelines to reduce your baby's risk of SIDS. Use a firm mattress with no loose blankets, pillows, or other soft bedding. Avoid a used crib mattress unless you're sure it was kept in pristine condition; otherwise it could harbor mold or bacteria.