Measured length of normal term infants changes over the first two days of life.

Measured neonatal length may be influenced by reluctance of the measurer to extend the infant's limbs against the normal flexor posture. As the degree of flexion decreases over the first few days of life, measured length may increase. We conducted a study of the effect of postnatal age on measured length and on inter-observer correlation. The study sample consisted of 101 healthy term newborns. Correlation between measurements made before age 2 hours by the study nurse and by regular nurses was excellent with a mean difference of 0.61 +/- 0.49 cm (r2 = 0.923). The mean measured length increased by 0.2 cm between admission and age 1 day (p = 0.057) and by a further 0.17 cm by age 2 days (p = 0.001). This study demonstrates that measured length appears to change over the first 2 days of life.