What is Average Baby Length by Month?
Understanding the size of the child or baby
A child’s length is measured from the top of the head to the base of one heel. This is the same as your height, but height is measured standing and length is measured when your baby is lying down.
The average body length of a full-term baby at birth is 19 to 20 inches (about 50 cm). But most newborns range from 45.7 to 60 cm.
Average length by age
If your baby is in the 50th percentile (average), that means 50% of babies are shorter than your baby and 50% of babies are taller.
How will your baby grow in the first year?
On average, babies grow 0.5 to 1 inch (1.5 to 2.5 cm) per month from birth to 6 months. Between the ages of 6 and 12 months, babies grow an average of 1 centimeter per month.
Your doctor will measure and weigh your baby during routine checkups and record his growth on a standard growth chart.
Your baby may grow more (growth stretches) or less at certain times. For example, children’s growth spurts:
- 10 to 14 days
- 5 to 6 weeks
- 3 months
- Four months
Your baby may be very fussy and want to eat more while growing. Growth spurts can last up to a week.
Can you predict how tall your child will be when he grows up as an adult?
It is difficult to predict your child’s future height based on your height as a child. When your child is a little older, you can estimate their adult height by doubling their height for boys at 2 years or doubling their height for girls at 18 months.
Length in premature infants or babies
Premature babies are measured and weighed as regularly as full-term babies. But doctors can use “age adjustments” to track a premature baby’s growth over time.
For example, if your baby is 16 weeks old but was born 4 weeks early, your pediatrician will cut off 4 weeks. Her adjusted age is 12 weeks. Your baby’s growth and developmental milestones should reach 12 weeks.
At 2 years of age or earlier, premature babies often catch up with their peers and your doctor no longer needs to correct their age.
Why is it important to track length?
Your pediatrician will measure your child’s height at each visit. This is an important step, but your doctor will likely be concerned about your baby’s monthly weight gain.
Babies need to double their birth weight by 5 months and triple their birth weight by one year.
Remember that children go through growth spurts. Your child’s monthly progress on the growth chart is not as important as the trend of your overall curve.
If your baby is not growing or has slow growth in the first year, your doctor may refer you to a specialist. An endocrinologist may do blood tests, X-rays, and body or brain scans to determine why your baby’s growth has stopped.
In rare cases, your doctor may want to check your child’s:
- Growth Hormone Deficiency
- Turner Syndrome
If necessary, the doctor may recommend medication or hormone injections.
What to do if you are concerned about your child’s or baby’s health?
Talk to your pediatrician if you’re concerned that your baby isn’t eating enough, reaching certain developmental milestones, or growing month to month.
Your baby’s diaper rash is a good indicator of whether he is getting enough to eat. Newborns need two to three wet diapers a day. After four to five days, the baby should be using five to six wet diapers a day. The frequency of bowel movements depends on whether your baby is breastfed or bottle fed.
Babies who are in the healthy growth range at each checkup are getting enough food. If you are concerned, talk to your pediatrician.
How much should my child or baby eat?
Every baby is different, but here are some general guidelines for how much and how your baby should eat:
Complementary foods should start between 6 and 8 months of age, although your doctor may recommend introducing solid foods earlier if your baby shows signs of readiness. After introducing solid foods, continue giving breast milk or formula until the baby is at least 1 year old.
The power frequency chart above can be used as a guide only. It is best to feed the baby when it is hungry. Unless specifically directed by your pediatrician, do not force your child to eat when he is not interested.
The Bottom Line
If you are concerned, talk to your pediatrician. They can determine if your child is growing as expected and is at a healthy height and weight for their age.