Understanding Infant Wind, Gut Development & Grunting
If you’ve ever marveled—or worried—about how gassy your baby is, you’re not alone. From burping and farting to full-on grunting marathons at 4 a.m., gas is one of the most commonly discussed topics among new parents and healthcare providers. Let’s unpack what’s really going on.
What Is “Wind” in Babies?
“Wind” can refer to two different types of gas:
- Swallowed air – which can be burped up after feeds.
- Intestinal gas – produced during digestion and passed as flatus.
Both are normal, though often misunderstood. For instance, a baby pulling up their knees, arching their back, or grizzling isn’t always a sign of trapped wind. Newborns have very basic movement patterns—scrunching and arching—which they use for all kinds of communication, from hunger to needing a change in position.
Where Does the Gas Come From?
Swallowed air is a normal part of feeding and, contrary to popular worry, most breastfed babies don’t swallow much air if latched well. However, feeding method, teat design, or latch issues can contribute to more air intake.
The bulk of the gas in a baby’s intestines, however, isn’t swallowed—it’s produced internally by bacteria fermenting sugars, especially lactose, in the gut. This process is essential to health, but can generate a lot of gas.
The Role of the Microbiome
Babies are born with a nearly sterile gut. Colonisation by beneficial bacteria begins during birth (especially vaginal birth), skin-to-skin contact, and feeding. Breastmilk, uniquely rich in special sugars (oligosaccharides), encourages the growth of “good” bacteria. Formula-fed infants tend to have different bacterial populations, and this affects the types and amounts of gas produced.
A study by Jiang et al. (2001) found that:
- Breastfed babies produce more odourless gases like hydrogen.
- Formula-fed babies produce more sulfur-based gases (e.g. hydrogen sulfide), which smell bad and may irritate the intestines.
Is Gas Painful?
In most cases, no. While some babies may squirm, grunt or cry briefly, this is typically due to immature gut coordination rather than actual pain. One common phenomenon is Infant Dyschezia—a normal developmental phase where babies strain and cry before passing soft stools. It’s not constipation or cause for alarm; it’s simply baby learning how to poop.
Colic & Gut Bacteria
Some babies do appear to suffer more significantly. Colic, defined as crying for over three hours a day on at least three days per week for at least three weeks, has been linked to imbalances in gut bacteria. Studies show that:
- Babies with colic have less bacterial diversity.
- They often have fewer beneficial bacteria like Bifidobacterium and Lactobacillus, and more potentially problematic strains like Proteobacteria.
Probiotic treatments—especially Lactobacillus reuteri—have shown some promise, particularly in breastfed babies, in reducing crying and fussiness.
The 4 A.M. Grunting Baby Syndrome
Grunting, straining, and squirming—especially during the night—is a near-universal parenting experience. Known as infant dyschezia or “grunting baby syndrome,” this behavior is often misread as pain from trapped wind or reflux. However, it usually reflects a developmental mismatch: babies are pushing with their abdominal muscles but haven’t yet figured out how to relax their pelvic floor.
It may be worse when babies spend a lot of time on their backs, which is important for safe sleep but not ideal for digestion. Cultures where babies are carried more often report less of this behavior, likely due to improved positioning and comfort.
What Helps (and What Doesn’t)?
✅ What can help:
- Tummy massage
- Warm baths
- “Frogging” or bicycling the legs
- Cuddling on your chest in a fetal position
- Infant massage
- Tag-teaming with a partner to hold baby upright overnight
❌ What to avoid:
- Rectal stimulation (e.g. with thermometers or wipes)
- Unnecessary dietary changes
- Laxatives or juice without medical advice
Final Thoughts
Yes—babies are gassy, and it’s usually totally normal. It’s part of their developing digestive system, growing microbiome, and immature coordination. Breastfeeding supports a healthier gut environment and reduces the likelihood of irritating gas. And remember, grunting and straining often looks worse than it feels to your baby.
When in doubt, get feeding assessed—especially if your baby seems unusually uncomfortable or symptoms are persistent. But most of the time, a little patience, some tummy rubs, and lots of cuddles are all your baby needs to get through this gassy, grunty, totally normal phase.
