Maternal reports are a valuable source of information about their children’s health conditions because the mothers observe their children daily and thus can be aware of symptoms or behavior patterns that might not be revealed on a given day. Hence, her observations are not dependent on those symptoms being apparent on the day of a particular medical visit, or on any medical visits having taken place.

On the other hand, most mothers do not have specific medical training, so they may not be familiar with what constitutes normal health and development for a child of a certain age. They also may not be familiar with some terminology used by medical providers to describe children’s health conditions.

Another potential problem with maternal reports of child health is recall bias. Maternal reports from this survey pertain to the child’s entire lifetime - a recall period of about three years. Previous studies have shown that recollection of health conditions fades with time, particularly for those that occurred long ago and are no longer symptomatic. Less serious illness are also less likely to be remembered.