Size

• When you assemble a new cot, make sure the mattress fits snugly against the sides of the cot. Do not buy a mattress that is too small. The size of the mattress is imperative to the safety of your child, according to the Baby Center.com. If two or more fingers can fit between the mattress and the sides of the cot, the mattress poses a risk of suffocation for your child. The gap provides space for your child to wedge her head into because she may not be able to lift it yet.
  
  

Organic Materials

• Buying organic mattresses might mean that your children do not have chemicals touching their skin. According to the Healthy Child.com, you might be fooled by an organic label into thinking that the mattress is non-toxic and flame-retardant. Although checking into the safety of organic and non-organic mattresses is important, some companies might be reluctant to release safety information. Check Consumer Reports for a list of the top mattresses based on safety requirements. The Better Business Bureau is also important because it can tell you whether there has been a complaint against a mattress company.
  
  

Mattress Materials

• Typical mattresses contain materials that some say might be toxic. Mattress makers use polyurethane foam to stuff mattresses that are not organic. According to Healthy Child.com, manufacturer material safety data sheets report that the toxic chemicals in polyurethane foam might cause serious health problems in infants, including possible cardiac arrhythmia and reduced pulmonary function. Waterproof coverings in typical mattresses have polyvinyl chloride with phthalates, which is environmentally unfriendly and perhaps toxic. While mattress makers use brominated fire retardants to slow the spread of fire, they have been linked to diseases including cancer. Understanding the materials that companies use for mattress materials is important to the health of your child.
  
  

Mattress Height

• Paying close attention to your children's height is important. When they grow, their mattress level needs to be lowered. Cots have mattress hangers that can be altered to make the mattress stay at the right height for the child. A mattress that is too close to the top of the crib poses a risk for growing children. They can pull themselves up and crawl out if the mattress is too high. If they crawl out, they might fall and hurt themselves.
  
  

Things to Look For

• Paying attention to the firmness of the mattress is important. A mattress should not sink or change shape when you place a baby on it or press your hand down. An abnormally soft mattress poses a risk of suffocation. It can create loose, bunched-up pieces of fabric that can get under your children's noses and cover their mouths.