Bamboo is a material that is frequently used for the inner layers of cloth diapers because it is more absorbent than cotton and is thought to have anti-bacterial qualities. While it is more expensive than some other options, bamboo is a soft fabric that is good for absorbent layers on your child's bed. Bamboo is also considered an eco-friendly option because the plant grows quicker than most other natural fibers.
Hemp is another natural fiber that is gaining popularity for its absorbent qualities. It is also stronger and more durable than cotton, but is often woven in a cotton blend to make the material softer. As with bamboo, hemp fabric has anti-bacterial properties and is an eco-friendly choice because it grows faster than cotton without the use of pesticides.
Flannel, interlock, and birdseye are all common cotton fabrics used for absorbency during potty training. The natural fibers absorb moisture well and are soft enough to use for bedding. One drawback to cotton is that it is not as absorbent as other materials, so you may have to use more layers of fabric to achieve the absorbency level you need.
Microfiber is an ultra-absorbent material that is suitable for use as an absorbent layer during night-time potty training. Microfiber requires fewer layers than other materials because it has a higher absorbency, but should not be used where it will be in direct contact with your child's skin. Besides being rougher to the touch than other materials, it can dry out skin with prolonged contact.
Sherpa blends can make a luxurious, absorbent bedding layer for your potty training toddler. You may have to look online to find sherpa terry blends that contain natural fibers. However, note that synthetic sherpa blends are not absorbent; in fact, urine may pool on the surface of the material.
Fleece is a good alternative to the plastic mattress covers that many families purchase during potty training. This fabric should only be used as the layer between the mattress and the absorbent layers because it provides a barrier for the urine rather than absorbing it. Alternately, you can use fleece pajama pants to provide protection to the mattress and bedding. Your child will still be wet, but the bedding will not be saturated.