Newborn Length - Average Length at Birth

Normal Values

At birth, the average length of a newborn is 50.5 centimeters if male, and 49.5 centimeters if female; these values ​​differ slightly according to the bibliographic sources consulted; other authors, for example, suggest an average interval between 48 and 53 cm, without distinction of sex.

During the nine months of gestation, therefore, the initial length of the fertilized egg increases by about 5,000 times.

To assess the state of nutrition and growth of the newborn, the birth weight is taken into consideration, on average between 3.2 and 3.4 kg. The length of the baby, however, is also of some importance.

Length measurement

We speak of length at birth, since - given the limited motor skills of the little one - the measurement of this parameter is much easier than the height. For this purpose, up to the age of two, an instrument called infantometer is used, which requires the simultaneous presence of two examiners; the first has the task of keeping the baby's head (placed in a supine position) well supported against the headrest. The orientation of the head must be such that the imaginary plane passing through the external acoustic meatus, and the lower margin of the orbit (Frankfurt plane), is perpendicular to the instrument. Finally, the second examiner has the task of slightly extending the lower limbs of the child, and placing the soles of the feet against the movable surface of the infant meter. The measured length must be approximated to 0.1 cm.

Growth of the child

After one month of life, the length of the newborn increases on average by about 5 centimeters.

On the first birthday, the baby reaches a stature of 70 - 80 cm (the length at birth increases by about 50%); this anthropometric parameter will then increase by about 10 centimeters during the following year. From this moment on, until the tenth year of age, the rate of statural growth slows down, so much so that the height increases only by 5-8 centimeters each Approximately 12 months. As anticipated, from the second year of age onwards, length is no longer measured but height, using the stadiometer (see article dedicated to the correct height measurement technique).

The growth of the child, however, does not only concern the size of the body, but also its proportions. In other words, the growth of the various body segments is not uniform; for example it is known that in the newborn the head represents about a quarter of the entire length of the body, while when the growth is complete the head represents only 1/7, 1/8 of the total length of the organism. Furthermore, with growth, the thorax becomes less and less cylindrical, and takes on an increasingly conical shape.

The hormonal upheaval that accompanies puberty is associated with a lively resumption of the rhythm of statural growth, which is integrated - according to a "harmonic alternation - with" weight gain.

The height reached by the child in adulthood is largely influenced by the nutritional status and by the genetic heritage inherited from the parents (see calculation module for the prediction of adult height).

Increase in weight and length of the newborn: percentiles (click on the image to enlarge)