Normal weight of a newborn
At birth, the average weight of a human being varies from 3200 to 3400 grams, while the normal range extends between 2.5 and 4.5 kg (for more information, see the article dedicated to the topic "weight at birth").
Weight loss after birth
After the birth, in the first week of life, the weight gain of the newborn is negative; in the first few days, in fact, there is a quantifiable weight loss of 5-10%, linked to stress induced by childbirth and the loss of fluids with faeces (meconium), breath, sweat and urine.
Weight loss is generally high for macrosomic newborns, while it appears to be lower in children with lower birth weight. It is also slightly higher in breast-fed infants (7% -10%) than in those fed artificial milk (5%).
Weight gain in the first few months
The weight lost in the first few days of life is normally recovered between the tenth and fourteenth day; after adapting to the new environment, the newborn begins to increase its weight quite clearly. Still on the basis of statistical data, the increase in weight of the "average" healthy newborn is:
- by 33% in the first six weeks;
- 25% in weeks seven to twelve;
- 20% in the weeks from twelve to eighteen.
More simply:
- after the first days of life, during the first five months, the weight gain of the newborn can be quantified in 150-200 grams per week, a rate that normally leads him to double his weight by the middle and the end of the fourth month of life.
- The pace of growth is generally maximum between the third and sixth week of life.
During the first year, birth weight is almost tripled, while the length increases by about 50%.
When to worry?
Weight is probably the best indicator of a child's state of nutrition and growth. It is very likely that the baby will not take enough milk if:
- the weight gain of the newborn is less than 18 g per day, 125 g per week or 500 g per month;
- the weight at 15 days of life is less than that registered at birth;
- the newborn urinates less than 6 times a day, with urine of pungent and concentrated odor (dark yellow that tends to orange), and evacuates hard, dry and rarely feces.
In addition to having a reduced weight gain, the poorly breastfed newborn can cry often, remain attached to the breast for a long time, appear lethargic and be dissatisfied at the end of feeding or refuse the breast.
Growth Percentages Weight and Height
Increase in weight and length of the newborn: percentiles (click on the image to enlarge - in males blue - in females pink)
The percentiles reported in the images indicate the number of infants of the same sex and of the same age that are of weight and length lower than a given value.
A 6-month-old baby with a weight corresponding to the 75th percentile (about 7.6 kg), for example, has 75% of the same sex peers whose weight is less than his and 25% higher.
