Researchers at the Centres for Disease Control and Prevention in the U.S., who surveyed 1,334 new mothers, also found that 40 percent had introduced solid food before their child reached four months old, and nine percent had even offered solids to their baby before they were four weeks old.
They also discovered that poorer, younger and less well educated mothers were more likely to introduce solids too early.
The reasons for this are thought to be that formula milk is seen as an expensive option, plus the myth that babies sleep better if fed on solids.
But the researchers warned that feeding solid foods to babies before they are six months old could increase their risk of developing chronic diseases such as diabetes and celiac disease.
They also fear that introducing solids prematurely could increase a child’s risk of obesity in later life.
But healthcare professionals may be partly to blame, it seems.
Kelley Scanlon, a co-author of the study and lead epidemiologist in the nutrition branch in the division of nutrition, physical activity and obesity at the CDC, told NBC News: ‘Fifty percent said that their health care provider told them it was time to introduce solid food.
‘That, for us, indicates that health care providers need to provide clearer guidance and really support women in carrying out the recommendation.’
When asked why they had started introducing solid foods, the most common reason the mothers gave was that their baby was old enough.
Others said that they did it because their child seemed hungry, because the baby wanted to eat the same food as its parents or because their doctor told them to.
The researchers also found that mothers whose babies were fed formula milk, as opposed to breast milk, were much more likely to offer solids too early -- 53 percent of mothers who fed their babies formula introduced solids before their baby was six-months-old, compared to 24 percent of mothers who exclusively breastfed.
Nutritionists are concerned that eating solid foods too early may mean that babies drink less milk and that, as a result, they may receive less nourishment.