Babies get gassy because their digestive systems are brand new and still learning how to process air and food. Before birth, a baby’s gut never had to deal with air at all. Once they start breathing, crying, and feeding, air enters the digestive tract, and the immature muscles of the intestines aren’t yet coordinated enough to move it out efficiently. On top of that, gut bacteria are just beginning to colonize, and as they break down undigested milk, they produce gas as a byproduct.
Why Newborn Digestion Produces More Gas
A fetus develops entirely in fluid for nine months, with zero experience processing air. From the very first breath, air becomes a constant companion in the gut. Some of that air gets swallowed during feeds and crying, and it has to go somewhere. It either travels back up as a burp or works its way through the intestines and comes out the other end.
The problem is that young babies can’t easily move gas through their system. Adults shift positions, flex abdominal muscles, or simply walk around to help gas along. A baby lying on their back doesn’t have those options. Their intestinal muscles are also still developing the wave-like contractions (called peristalsis) needed to push gas through efficiently. So even a normal amount of gas can become uncomfortable simply because it gets stuck.
As the gut matures, bacteria naturally colonize the intestines and begin breaking down components of breast milk or formula that weren’t fully digested higher up in the tract. These bacteria produce gas as a byproduct of their work. This is completely normal and happens in every human gut, but a baby is experiencing it for the first time and doesn’t yet have the muscle coordination to deal with it comfortably.
Air Swallowing During Feeding
The single biggest source of infant gas is swallowed air, and feeding is when most of it gets in. Bottle-fed babies tend to swallow more air than breastfed babies, particularly when the nipple flow rate is wrong. If the holes in a bottle nipple are too large, milk comes out faster than the baby can manage, and they gulp air along with it. A good rule of thumb: cold formula should drip from an inverted bottle at about one drop per second. Faster than that, and the nipple flow is too high.
Feeding position matters too. A baby who drinks while lying flat swallows more air than one held at a slight incline. For breastfed babies, a shallow or improper latch lets air sneak in around the seal between the baby’s mouth and the breast. If you hear clicking sounds during nursing, that’s often a sign the latch is breaking and re-forming, pulling in small pockets of air each time.
The Crying-Gas Cycle
Crying is another major way babies swallow air, and it can create a frustrating feedback loop. A baby with trapped gas cries because of the discomfort. That intense crying causes them to gulp down even more air, which produces more gas, which leads to more crying. Babies with colic, defined as crying more than three hours a day for more than three days a week in an otherwise healthy infant under three months, are especially vulnerable to this cycle because the sheer duration of their distress means a lot of extra air intake.
Formula Sensitivity and Lactose Issues
Some babies produce excess gas because their digestive system reacts to specific components in formula. The proteins in standard cow’s milk formula, casein and whey, can be difficult for certain babies to break down. For these infants, hypoallergenic formulas use the same proteins but pre-break them into much smaller pieces that are easier to digest.
Lactose, the sugar naturally present in all mammalian milk, requires a specific enzyme to digest. Most full-term babies produce plenty of this enzyme, but premature babies sometimes don’t make enough of it yet. This temporary condition, called developmental lactase deficiency, usually resolves on its own within weeks to months after birth. When lactose isn’t broken down properly, it sits in the intestines and ferments, producing gas, bloating, and sometimes watery stools. For the small number of babies who truly can’t handle lactose, formulas that replace it with glucose or sucrose are available.
Does a Breastfeeding Mother’s Diet Matter?
This is one of the most common questions new parents ask, and the answer is less clear-cut than most people expect. There is limited scientific research proving that specific foods in a breastfeeding mother’s diet cause gas in her baby. Spicy foods, in particular, have not been shown to cause discomfort in breastfed infants despite the widespread belief that they do.
Many mothers report that foods like beans, onions, garlic, kale, and peppers seem to make their baby gassier. But just as many babies tolerate those same foods without any issue. The fiber and sugars that make you gassy when you eat broccoli don’t pass into breast milk in the same form. What does transfer are flavor compounds and trace nutrients, not the undigested carbohydrates that produce gas in your own gut.
That said, patterns are worth paying attention to. If you consistently notice your baby getting fussy or gassy after you eat a particular food, it’s reasonable to eliminate that food for a week or two and see if things improve. Just don’t restrict your diet broadly based on general lists of “gassy foods” without observing an actual pattern first.
Physical Techniques That Help
Because babies can’t reposition themselves to move gas along, you can do it for them. The simplest and most effective technique is bicycle legs: lay your baby flat on their back and gently move their legs in a pedaling motion. This compresses and releases the abdomen rhythmically, helping trapped gas bubbles work their way through the intestines.
Supervised tummy time serves double duty. The gentle pressure of lying on their stomach pushes against gas pockets and encourages them to move out. It also strengthens the upper body and helps prevent flat spots on the head. Even a few minutes of tummy time after a feed (once the baby has been burped) can make a noticeable difference.
Burping during and after feeds, rather than only at the end, catches swallowed air before it travels deeper into the digestive tract. For bottle-fed babies, pausing every two to three ounces to burp is a good habit. For breastfed babies, switching breasts is a natural burping opportunity.
Over-the-Counter Gas Drops
Simethicone drops are the most commonly used remedy for infant gas. They work by breaking large gas bubbles into smaller ones, which are theoretically easier to pass. These drops are generally considered safe, with minimal side effects. However, the evidence for their effectiveness is mixed. Some studies show benefit when simethicone is combined with probiotics, but well-controlled trials comparing simethicone alone to a placebo have not consistently shown a clear advantage.
Probiotic drops have also gained popularity, but the research here is similarly complicated. A meta-analysis of small trials with breastfed babies found that one specific probiotic strain reduced crying time after about three weeks of use. But a larger, more rigorous trial that included both breastfed and formula-fed infants found no benefit. In fact, the probiotic group in that study fussed slightly more than the placebo group, particularly among formula-fed babies. The takeaway: probiotics aren’t a reliable fix for infant gas across the board.
When Gas Is Just Gas
Nearly all infant gas is normal and temporary. The digestive system matures rapidly over the first three to four months, and most babies become noticeably less gassy as their intestinal muscles get better at moving things along and their gut bacteria stabilize. If your baby is gaining weight normally, feeding well, and having regular bowel movements, the gas is almost certainly part of ordinary development, not a sign of a deeper problem.
Gassiness that comes with persistent vomiting, bloody stools, refusal to eat, or failure to gain weight is a different situation and worth bringing up with your pediatrician. But for the vast majority of babies, gas is simply the cost of a digestive system booting up for the first time.