Gassy tummy. All babies get gassy tummies! in order to grow, babies take in 100 kcal for each kilogram they weigh! this is a lot of hard work on their digestive system. (imagine digesting 7000 calories per day........You would be gassy too!) babies have immature gastrointestinal tracts too. Digestion, and gassiness, often get much better between 4-6 weeks of age.
Multiple factors. Infants naturally produce gas as part of the digestive process. Gas is a natural byproduct of both breast milk and formula. Breastfed babies may also produce more gas according to what is in mom's diet. Legumes, some vegetables and sometimes dairy products may lead to increased gas in your baby. Babies also get gas from swallowing air during feeding. This is why burping is important.