A recent study* by nutrition researchers at the Center for Disease Control and Prevention shows that 40% of mothers (1334 of them in 2005 -2007) fed solids to their infants before 4 months of age, though breastfeeding mothers did so half as often as those who were formula fed (24% vs 53%).  Mothers with higher educational level and higher incomes also did so less frequently (many of these were the same mothers included in the breastfeeding group. Breastfeeding advocates especially are concerned because of the potential for infants to get less breastmilk, and the potential for obesity more infections. 

Given the confusion that surrounds feeding babies, from birth through the first year, however, it’s not surprising to hear that many parents start solids too soon, especially when you examine the history of when baby foods were introduced. Before 1920, solids were withheld until a year of age.  In the 1930s, as now, these feedings usually began between 4-6 months--and starting with the broader availability of packaged foods in the 1940s, babies were exposed earlier and earlier (in fact, as early as 3 days of age for cereal). So mothers raised that way (they are grandmothers now) understandably look at their own histories and often offer advice that conflicts with their grandchildren's doctors and more contemporary thinking.

As explained What to Feed Your Baby: Cost-conscious Nutrition for Your Infant (June, Rowman & Littlefield), when solids are introduced (and which ones) should be determined by a variety of factors besides age alone. Yes, breastfeeding is a major determinant, but so is whether the child has reflux, difficulty gaining weight, the tendency to obesity, allergy, celiac disease or even constipation. 

* Clayton HB, Li R, Perrine CG, Scanlon KS. Prevalence and reasons for introducing infants early to solid foods: variations by milk feeding type. Pediatrics. 2013 Mar 25. [Epub ahead of print, PMID:23530169]