The best foam mattresses

If you decide to go with foam because it's lightweight, density is the most significant sign of quality.

Dense foam. The best foam mattresses are firm and heavy and resilient--they bounce back quickly when you squeeze them in the center and the edges with both hands. To assess foam quality, compare the weight of different models. That's not always easy to do in a store, but if you're able to lift several mattresses, do it. In general, the heavier the foam mattress, the denser (and better) the foam. You can give the mattress a squeeze test in the center by pressing your palms into both sides at once. A dense mattress won't allow you to press very far.


The best innerspring mattresses

If you decide on an innerspring mattress, follow this general rule: the more layers and the better quality of those layers, the better the mattress.

High coil count and low steel gauge. "Coil count," the number of springs or steel coils a mattress contains, is a popular marketing point. But a generous coil count doesn't always mean a firmer mattress. The cheapest innerspring baby mattresses may have fewer than 80 coils and more expensive models may have more than 280 coils, but a model with 150 coils could be firmer than one with 200. How? The gauge of steel in those 150 coils may be thicker than the steel in the 200-coil mattress. Steel gauge for mattress coils ranges from 12.5 to 19; the lower the number, the thicker the steel. Thicker is stronger. So look for a moderate to high coil count--135 to 150 coils is a good midrange--and a lower coil steel gauge, 15.5 or below.

Coir fiber or wrap pad as the insulator pad. On top of the coils is an insulator pad that keeps the coils from poking through a mattress' cushioning layers (see below) and bothering your baby. The best insulator pad is made from coir fiber--shredded and woven coconut shell--but fiber wrap pad, also called "rag" or "shoddy" pad, which is made from miscellaneous and pressed scraps of cloth, is also good. Coir fiber is more expensive than fiber wrap pad, but either works well. The lowest quality insulator pad is made from woven polyester. Because it tends to form pockets over time, becoming concave where most of the baby's weight rests, it's less durable.

Foam or cotton cushioning layers. The next layer in the mattress sandwich is the cushioning, which may be made of foam, cotton, or polyester. Foam and cotton are signs of quality, though they contribute to the price. Polyester, which is less expensive and increasingly pervasive because the cost of foam to manufacturers has been rising, isn't ideal because of its tendency to form pockets.

Border rods. They go around the perimeter of the mattress top and bottom, and are the thickest pieces of steel a mattress contains. Don't buy innerspring mattresses that don't have border rods. Border rods provide extra firmness, durability, and edge support so a mattress won't sag when your baby stands or walks near the edge. Consider border rods a must-have.

Cover. Encasing the entire mattress is a fabric or vinyl cover. Fabric breathes more than vinyl, but ventilation holes in a vinyl covering help air circulate. The more vents the better. A thicker or layered vinyl covering better resists leaks, stains, punctures, and tears, so go with vinyl over fabric. Look for at least a triple laminated ("3-ply") covering, which will give a mattress a tougher shell, adding to its longevity. Unlike a cloth cover, vinyl also acts as a barrier to dust mites.