Baby Growth Spurts: The Ages the AAP Gives, and What the Research Found

One set of measurements comes from a 1992 study in the journal Science by Lampl and colleagues. They measured the length of 31 healthy infants weekly, twice a week or daily during their first 21 months. Length came in bursts of 0.5 to 2.5 cm, separated by stretches of 2 to 63 days with no measurable growth. The authors called the bursts aperiodic: they did not arrive on a schedule.

The same paper says the data suggest 90 to 95 percent of normal development during infancy is growth-free, with length added in bursts. It was a small study and it measured length, not weight. It supports the idea that babies grow in spurts. It does not say when those spurts happen.

A 2024 editorial in Nutrients by Riccardo Davanzo and Maria Elisabetta Baldassarre looked at what else has been published. After a PubMed search it judged six articles relevant, and described the literature as scarce and unsubstantial. It says neither Lampl’s studies nor an earlier study of weight in low-birth-weight infants identified a regular timing or an approximate age for the spurts. An editorial is the authors’ reading of the evidence, not a guideline.

The AAP’s page on the first month says most babies gain weight very quickly, especially during growth spurts, which typically happen at around 7 to 10 days old and again between 3 and 6 weeks old. The same page says the average newborn gains almost an ounce (28 grams) a day.

For the months after, the AAP describes averages rather than spurts. From 1 to 4 months, it says, babies continue growing at about the same rate they set in their first few weeks, typically gaining 1.5 to 2 pounds (0.7 to 0.9 kg) and growing 1 to 1.5 inches (2.5 to 4 cm) each month. It adds that these figures are only averages.

The fixed calendar, with spurts at 2 to 3 weeks, 6 weeks, 3 months and 6 months, is one the 2024 editorial says some health care institutions use. The editorial’s conclusion is that growth spurts in the first year seem inadequately supported by current scientific knowledge. No AAP or NHS page opened for this guide gives a schedule after the first month.

The NHS describes cluster feeding as a baby wanting to feed even more frequently, sometimes constantly, over a period of time. It says this usually happens during the first 3 to 4 months, can happen during the day or night, and is very normal and nothing to be concerned about. It also says your baby may cluster feed for a few days when they are going through a growth spurt.

If you are breastfeeding, the NHS’s description of supply is the useful one: generally, the more your baby feeds, the more breast milk you’ll produce. It advises letting your baby guide how often to feed, especially in the early days, rather than sticking to set times. The 2024 editorial makes a related argument. It says changes in a breastfed baby’s feeding behaviour are better explained by the physiology of lactation, including normal variation in milk production, than by a biological growth trigger, and notes that the more time a baby spends sucking at the breast, the greater the stimulus to produce milk.

If you are formula feeding, the NHS says you can cluster feed formula milk, but that it is important not to overfeed. The cues it lists for when a baby needs a break are splaying fingers and toes, spilling milk out of the mouth, stopping sucking, turning the head away or pushing the bottle away; a full baby, it says, will not want the bottle any more or may fall asleep. The AAP’s pediatrician Q&A says a baby who still acts hungry after finishing a bottle, or wants to eat more often than usual, may be ready for larger feedings.

Not every bout of sucking is hunger. The AAP notes that babies suck for comfort as well as for food, and that it can be hard at first for parents to tell the difference.

One study measured sleep and growth together. In a 2011 paper in the journal Sleep, Lampl and Johnson compared daily sleep diaries for 23 infants with their growth in length. Bursts of growth were associated with more total daily sleep and more sleep bouts, and peaks of about 4.5 extra hours of sleep and/or 3 extra naps a day lined up with the bursts, within 0 to 4 days.

So this study found more sleep around growth bursts, not less. It was small, and it shows an association rather than a cause. For the other reasons sleep can shift at certain ages, see our sleep regressions guide. Whatever is behind a broken night, the rules in our safe sleep guide stay the same.

The AAP’s guide to growth charts says what pediatricians hope for is consistency. A child at the 10th percentile is no better or worse off than one at the 90th; what matters most is the trend. It says one point on a chart is not as useful as five points over time, and that the rate and trend of growth matter more than the specific number.

It also gives the broad shape of the first year: babies double their weight by about 6 months and triple it by around 1 year. The AAP’s page on 8 to 12 months adds that you should not be alarmed if your child follows their own curve rather than the typical one in the middle, as long as it is an upward curve.

The 2024 editorial makes a related point about the charts themselves: the growth charts the WHO recommends for children under 2 do not suggest any increase in growth velocity in this age group. Our percentile calculator gives WHO percentiles for weight and length from 0 to 24 months, and our WHO growth chart draws the same curves. Neither replaces your pediatrician’s measurements.

The AAP’s markers are diapers and growth. It says a baby should have 2 to 3 wet diapers a day in the first few days, and at least 5 to 6 a day after the first 4 to 5 days. At checkups, your pediatrician plots weight on a growth chart, and the AAP says babies who stay in healthy growth percentile ranges are probably getting a healthy amount of food.

The NHS lists signs that a breastfed baby is feeding well: seeming calm and relaxed during feeds, coming off the breast by themselves when they have had enough, and appearing content and satisfied after most feeds. It expects at least 6 wet nappies every 24 hours from the fifth day onwards.

If you are concerned your baby wants to eat all the time, even when full, the AAP says to talk with your pediatrician. If you are worried your baby is not getting enough breast milk, the NHS says to talk to your midwife, health visitor or a breastfeeding specialist as soon as possible.

Timing. The AAP gives two newborn windows, 7 to 10 days and 3 to 6 weeks. Lampl’s 1992 data found bursts of growth, but aperiodic ones, and the 2024 editorial says the measurement studies it discussed, Lampl’s and an earlier one by Greco, did not identify a regular timing or approximate age. This page does not pick between them.

What the extra feeding means. The NHS links cluster feeding to growth spurts. The editorial argues that for breastfed babies the same changes are better explained by the physiology of lactation. The practical advice does not change: the NHS says to let your baby guide how often to feed.

Wet diapers. The AAP says at least 5 to 6 a day after the first 4 to 5 days; the NHS says at least 6 every 24 hours from the fifth day.

This page explains a pattern. It cannot tell you whether a change in your baby’s feeding, sleep or weight needs attention. The AAP’s advice on growth is to talk with your pediatrician if you have any questions. Crying has its own guide: our guide to why babies cry covers the patterns and what helps.