Stomach While no single position is best for everyone, sleeping on your stomach should be avoided. Go with an extremely flat pillow or without a pillow entirely. Stomach sleeping puts the neck in a position of extreme turning and backward bending, resulting in an increased amount of pressure on the joints and muscles.

Back Use a flatter pillow so that the head is not tipped forward and the neck needs less support.

Side The thickness of the pillow should be enough to fill the space between the tip of the sleeper’s shoulder and ear. Pillows that are thicker at the base, with a curved shape, made out of memory foam, or with an adjustable water bladder built into them work best. Synthetic fills work well and are relatively inexpensive, but should be replaced when they lose their support and become too easy to compress. Down is expensive and it does a relatively poor job of supporting the head.

Pregnant During pregnancy, the ligaments (the cords that hold your bones together) become slightly more flexible throughout the body, so a firmer pillow should be used. As most pregnant women side-sleep, a thicker pillow should do the trick.

Children If your child stays under the covers and in a relatively normal position, start with a thin, synthetic-fill pillow. An adult-size pillow will be too big or too firm to support the child in a comfortable position.

Allergies Choose a synthetic pillow appropriate for your sleeping style and use a dust-mite cover.