Growth and Your 1- to 3-Month-Old

Like they did as newborns, most babies grow quickly in weight and length during the first few months of life.

How Much Do Babies This Age Grow?

The first month of life was a period of rapid growth. As a 1- to 3-month-old, your baby will continue to grow at a similar rate, while also gaining 1 to 1.5 inches (2.5 to 3.8 centimeters) in length per month. These are just averages — your baby may grow somewhat faster or slower, and is likely to experience growth spurts as well as times of slower growth.

The amount your baby eats at each feeding will gradually increase and by the end of 3 months, weight gain will slow from 1 ounce (30 grams) to about 2/3 of an ounce (20 grams) a day.

Your doctor will measure your baby's weight, length, and head circumference and track his or her growth pattern on a standardized growth chart (there are different charts for boys and girls). Generally, whether your baby is large, small, or medium-sized, as long as your child's growth pattern stays consistent over time, chances are excellent that he or she is doing fine.

If your baby is born prematurely, keep in mind that growth and development should not be compared with that of a full-term child.

Preemies will need to be followed more closely and may need to be weighed weekly during the first months to make sure they are growing properly. They have some catching up to do!

Should I Be Concerned?

If your 1- to 3-month-old is not growing at the expected rate, or the growth rate slows, your doctor will want to make sure your baby is getting enough to eat.

The doctor may ask you about:

  • How many feedings a day your baby gets. A breastfed baby may feed 8 to 12 times in a 24-hour period; bottle-fed babies usually eat less frequently, perhaps every 3 to 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 eat about 3 to 4 ounces (90 to 120 milliliters) a feeding during the first month, with an extra ounce (30 milliliters) per feeding for each additional month.
  • How often your baby urinates. Babies should have at least 4 to 6 wet diapers a day.
  • How many bowel movements your baby has each day, and their volume and consistency. Breastfed babies' stools should be soft and slightly runny. The stools of formula-fed babies tend to be a little firmer, but should not be hard or formed. Frequency of bowel movements depends on age and type of feeding.

Most of the time, a baby's growth will simply be tracked over the next few months during routine well-baby visits. But if your doctor is concerned about your baby's growth, he or she will want to see your baby more frequently. Breastfeeding mothers may benefit from meeting with a lactation (breastfeeding) counselor who can make suggestions to improve technique.

You may have heard the term "failure to thrive," which describes a baby who isn't gaining weight normally but does not get at the cause. Sometimes, there may be a medical reason for slow growth, which would require further evaluation.

Call your doctor if your baby is not feeding well or if you have concerns about your baby's growth or development. Call the doctor immediately if your infant is vomiting every feeding, not wetting his or her diapers, has a fever, or seems listless or unresponsive.

What's Next?

In most cases, breast milk or formula is all a baby needs for the first 6 months of life, but some doctors may recommend introducing iron-fortified rice cereal at 4 months. Talk with your doctor before starting any solids or changing formula.

Reviewed by: Mary L. Gavin, MD
Date reviewed: September 2011

Kids Health

Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

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