Length of the Newborn - 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 depending on the bibliographic sources consulted; other authors, for example, suggest an average interval between 48 and 53 cm, without distinction of sex.

Thus, during the nine months of gestation, the initial length of the fertilized egg increases by 5, 000 times.

To assess the state of nutrition and the growth of the newborn, we take into consideration above all the birth weight, on average between 3.2 and 3.4 kg. Even the length of the small, however, plays a certain importance.

Length measurement

We talk about length at birth, because - given the limited motor skills of the small - the relief of this parameter is much easier than the height. To this end, until the age of two, an instrument called an infantometer is used, which requires the simultaneous presence of two examiners; the first one has the task of keeping the child's head (placed in a supine position) well supported against the headrest of the instrument. The orientation of the head must be such that the imaginary plane passing through the external acoustic meatus, and the lower edge of the orbit (Frankfurt plane), is perpendicular to the instrument. Finally, the second examiner has the task of slightly extending the child's lower limbs, and positioning the soles of the feet against the movable plane of the infantometer. The detected length must be approximated to 0.1 cm.

Child growth

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

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

The baby's statural growth, however, not only affects 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 completed the head represents only 1/7, 1/8 of the overall 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 revival of the statural growth rate, which is integrated - according to a harmonious alternation - with the weight growth.

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

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