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Average Baby Weights
Children develop at different paces, but the average birth weight of a full-term male baby is 3.3 kilograms (kg) and 3.2 kg for a female. Growth charts can provide a guide to the average weight of a baby.
First, it is worth noting that average weight is not typical weight. Just like adults, babies come in all shapes and sizes.
If a baby’s weight is in a lower percentile, this does not necessarily signal a problem with their growth or physical development. With this in mind, using a weight chart can help a person generally track their baby’s growth.
This article describes a baby’s average weight month by month from birth and explores what can affect it.
World Health Organization (WHO) Guidance
The World Health Organization (WHO) weight chart is suggested for infants under the age of two. According to the WHO, the average birth weight of a full-term male baby is, or 3.3 kilograms (kg). The average birth weight of a full-term female is.
The average weight of a baby born at 37 to 40 weeks ranges from 5 lb 8 oz to 8 lb 13 oz. This amounts to 2.5 to 4 kilograms. At delivery, consider a low birth weight to be less than 5 lb 8 oz, or 2.5 kg.
It is for babies to lose around 10% of their weight during the first week after birth. This decrease is mostly due to fluid loss and usually nothing to worry about. Within a week, most babies regain this weight.
Baby Weight Chart By Age
Weight charts can help someone tell what percentile their baby’s weight falls into.
For example, if their weight is in the 60th percentile, 40% of babies of the same age and sex weigh more, and 60% of these babies weigh less.
This does not necessarily mean that any baby weighs too much or too little. It can simply indicate where a baby’s weight falls on a spectrum.
The chart below shows baby weights in the 50th percentile, which refers to the average weight. Because male babies typically weigh slightly more than female babies, the chart is divided according to sex.
What To Expect
Babies usually gain weight most rapidly during the first 6 months of their life.
Breastfed or chest-fed infants typically gain weight more slowly than formula-fed infants. It is for babies to lose weight in their first week of life. By the time they are two weeks old, they typically gain this weight back.
Although this can vary, infants typically weigh their birth weight by their first birthday and have doubled their birth weight by the age of four months. However, growth patterns do not follow a clear schedule.
Some babies gain weight steadily and stay in the same percentile, or close to it, for several months.
Others gain weight rapidly, signaling a growth spurt, which can occur at any time. This may move a baby into a new weight percentile.
What Affects Baby Weight?
It is important not to focus on weight as the only indicator of physical development. Other measurements of this development include the baby’s length and head circumference.
Considering all three measurements gives doctors an idea about how the baby is growing, compared with other babies of the same age and sex.
Meanwhile, it is also important to consider other developmental milestones. There are a number of age-specific milestone checklists out there, including one from Pathways.org that has been approved by the American Academy of Pediatrics (AAP) and the National Association of Pediatric Nurse Practitioners.
Nutrition
Weight gain and growth rates can also depend on whether the baby consumes breast milk or formula.
Chest or breastfed babies gain weight and grow more than formula-fed babies during the first year.
However, growth generally follows a similar trend for both chest or breastfed and formula-fed babies. Weight continues to fluctuate even after the baby starts eating other foods.
Medical Conditions
Underlying health issues can cause a baby to gain weight more slowly. For example, babies with congenital heart irregularities may gain weight at a than babies without this condition.
Health issues that affect nutrient absorption or digestion, such as may also lead to slow weight gain.
Prematurity
Babies born prematurely may grow and gain weight more slowly during their first year than babies born at full term.
However, many premature babies gain weight rapidly and “catch up” by about their first birthday.
Summary
The average birth weight for full-term male babies is, or 3.3 kilograms (kg). For female babies born full-term, the average birth weight is, or 3.2 kg.
Baby weight charts can help a healthcare team track a baby’s physical development by comparing the baby’s weight with that of an infant of the same age.
Still, when evaluating a baby’s physical development, a doctor usually looks for steady growth rather than a target percentile. Even if a baby’s weight is in a lower percentile, it will not necessarily lead to them developing into a small adult, just as longer babies do not necessarily become tall adults. Knowing about average weights by month can help people gauge their babies’ physical development, but doctors also look for other important indicators, such as length and head circumference.
