Many babies are being introduced to solid food too early.

The American Academy of Pediatrics recommends that babies begin receiving solid food at the age of four to six months.

But a new study found that about 40 percent of mothers introduced their babies to solid foods before they were four months old.. and some did it as early as four weeks of age.

Mothers who fed their babies with formula were about twice as likely to introduce solid foods early, compared to those who breast-fed.

The study is published online in the journal Pediatrics.