About 40 percent of mothers in the U.S. start giving their babies solid food before 4-6 months of age, according to a new study.

Babies should be exclusively fed with breast milk for the first 6 months, the American Academy of Pediatrics had earlier said in a policy statement. The Academy had advised parents to introduce solids along with breast milk after the baby was 6 months or older.

The present study was based on data obtained from more than 1,300 mothers enrolled in the national longitudinal Infant Feeding Practices Study II (2005-2007). About 40.4 percent mothers reported to have fed their babies solid food before age 4 months and the prevalence was highest in formula-fed babies with 52.7 percent, followed by mixed-fed infants with 50.2 percent and breast-fed babies with 24.3 percent.

Mothers included in the study cited reasons like "My baby was old enough," "My baby seemed hungry," and "It would help my baby sleep longer at night" for the early introduction of solid food for the babies. Many mothers said that their healthcare gave them the go-ahead to feed the baby with solid food.

"Clearly we need better dissemination of the recommendations on solid food introduction. Health care providers need to provide clear and accurate guidance, and then provide support to help parents carry out those recommended practices," said Kelley Scanlon, an epidemiologist with the C.D.C. and an author of the study, reports the New York Times.

Early introduction to solid food cuts down the benefits of breastfeeding. Also, as the baby's body isn't prepared to process solid food, introduction of solids may lead to chronic diseases later in life, according to a statement released Monday by the American Academy of Pediatrics.

A related study published in 2011 in the Maternal and Child Health Journal also found that about 62 percent report that they have introduced solids in their child's diet between 4 and 6 months of age. Another study from Pediatrics found that infants fed with solid foods before age 4 months had an increased risk of obesity at age 3 years.

The study is published in the journal Pediatrics.