Your Baby's Growth: 3 Months

Most babies continue to grow in weight and length this month. But you might notice that your baby isn’t growing quite as fast as in the first few months of life.

How Much Will My Baby Grow?

Your baby will gain about 1 to 1½ inches (2.5–3.8 centimeters) in length and 1½ to 2 pounds (681–907 grams) in weight this month. But it’s also OK if your baby grows a little more or a little less.

At this point, you know the signs that your baby is hungry or full. When hungry, your baby may seem restless, cry, stick out their tongue, or suck on their hands and lips. When full, your baby probably doesn't seem interested in feeding or just falls asleep after feeding.

Your baby can go through periods of increased hunger and fussiness. This increase in hunger means your baby is going through a period of fast growth (a growth spurt). If you breastfeed, you might find your baby wants to eat more often (sometimes every hour!) during certain times of the day. This is called "cluster feeding." Formula-fed babies may want to eat more often or will drink more formula than usual during feedings.

How Is My Baby’s Growth Checked?

At your baby’s checkups, the health care provider measures your baby's weight, length, and head circumference. They put this information into a growth chart (there are different charts for boys and girls). The growth chart lets them see if your baby is growing at the right pace. Whether your baby is big or small for their age now doesn’t necessarily mean they will be big or small when they are older. What matters most is that your baby is growing steadily.

Babies who were born prematurely may need special formula or “fortifiers” added to the formula to give more nutrients and calories. Doctors may want to check growth more often during the first few months to make sure the baby is growing enough. It can take a while for babies born early to catch up, but as long as they are growing steadily, it’s usually OK.

What Happens if My Baby’s Growth Is Slow?

A baby’s growth may be slower or faster at times. And sometimes a baby can change to a different growth curve. As long as the growth trend over time is steady, there is probably nothing to worry about. The doctor will ask you questions and check your baby to see if you need to make any changes in feeding or whether any testing is needed. 

They will ask about:

• how many feedings a day your baby gets: At 3 months, a breastfed baby may feed about 8 times in a 24-hour period; bottle-fed babies usually eat less often, about every 4 hours.
• how much your baby eats at each feeding: A baby generally nurses for at least 10 minutes, should be heard to swallow, and should seem satisfied when done. Bottle-fed babies may drink up to 6–7 ounces (177–207 milliliters) — some more and some less — at each feeding.
• how often your baby pees: Babies should have at least 4–6 wet diapers a day.
• how many bowel movements (BMs or poops) your baby has each day and if they are firm or runny: The number of poops can vary a lot. Some breastfed babies poop with every feeding, but they also might not poop for a day or more. Most formula-fed babies poop at least once a day but others poop more or less than that. Breastfed babies' stools tend to be soft and slightly runny. The stools of formula-fed babies tend to be a little firmer. Whether your baby is breastfed or formula-fed, their pooping pattern is probably OK as long as the poop is not hard and doesn't have mucus or blood in it.

The doctor may want to see your baby sooner than the next regular checkup, just to make sure your little one is growing OK.

Could My Baby Gain Too Much Weight?

You don’t need to worry about your baby gaining too much weight at this age, so feed your baby whenever they seem hungry.

Still, it’s OK to start some healthy habits with your baby:

• Stop a feeding when your baby seems satisfied. As long as your baby doesn't have trouble gaining weight, you don’t need to “top off” a feeding with a few extra minutes on the breast or more formula.
• Babies this age shouldn’t have juice, cereal, or other foods. They get the nutrition they need from breast milk or formula. Also, starting juice or foods early can cause them to gain too much weight.

Babies this age don’t need extra water. Never water-down formula to try to slow weight gain.

Be aware that sometimes when your baby fusses or cries, it's not a sign of hunger. They might just want to play or be with you.

When Will My Baby’s Growth Be Checked Next?

Unless your baby needs to come in sooner, the doctor will see your baby and check growth at the 4-month checkup. Your baby will continue to grow in length and weight at a steady rate. By 4 months, most babies have doubled their birth weight.

Call the doctor if you have any concerns about your baby’s growth or health.