Infancy Period


Infancy period, traditionally, is the time from 1 month to 1 year of age. Because of the growth and learning potential that occurs, the first year of life is a crucial one.

Physical development during the infancy period

  • Weight. Most infants double their birth weight at 4 to 6 months and it triples at 1 year. A weight gain of 2 lb per month during the first 6 months is typical among infants. During the second 6 months, the expected weight gain is approximately 1 lb per month.
  • Height. Height like weight is ideally assessed if plotted on a standard growth chart. The average birth length of an infant is about 20 inches. During the first year an infant increases in height by about 50 %. In early months the growth is apparent in the trunk while it becomes more apparent as lengthening of the legs during the second half of the first year.
  • Head circumference. Rapid brain growth is reflected by a rapidly increasing head circumference. By the end of the first year of life, the brain has already reached two-thirds of its adult size.
  • Teeth. By 6 months of age, the first baby tooth which is typically ca central incisor erupts. The eruption is followed by a new one monthly. Usual ages of baby tooth eruption by tooth type are as follows:
    1. Central lower incisor – 6 to 10 months
    2. Upper central incisor – 8 to 12 months
    3. Upper lateral incisor – 9 to 13 months
    4. Lower lateral incisor – 10 to 16 months
    5. Upper cuspid – 16 to 22 months
    6. Lower cuspid – 17 to 23 months
    7. Upper first molar – 13 to 19 months
    8. Lower first molar – 14 to 18 months
    9. Lower second molar – 23 to 31 months
    10. Upper second molar – 25 to 33 months
  • Gross motor development. To assess the development of gross motor skills in infants, four positions should be observed. The positions are as follows:

Ventral suspension position

This is the appearance of the infant when held in midair on a horizontal plane, supported by a hand under the abdomen. With this position, the infant’s head is allowed to hang down with little effort on control.

  1. One month old infants lift the head momentarily and drop it again. Flexion of elbows, hip extension and knee flexion may be observed.
  2. By two months of age, the head is held in the same place as the rest of their body. This signifies a major advancement in muscle control.
  3. A month after, the head is lifted and maintained well above the plane of the rest of the body in ventral suspension. It is at this month where a Landau reflex is developed. Landau reflex is the extension of the infant’s head, legs and spine when held in ventral suspension. Most infants continue to present this reflex until 6 months of age. Inability to perform this reflex would suggest further evaluation for possible motor weakness, cerebral palsy, or other neuromuscular defect.
  4. When Landau reflex diminished, the infant then demonstrates a parachute reflex. By 6 to 9 months of age, infants suddenly lower towards the examining table while extending the arms as if protecting themselves when held in a ventral suspension position. An inability to demonstrate this reflex would suggest cerebral palsy because they flex their extremities too tight.

Daisy Jane Antipuesto RN MN

Currently a Nursing Local Board Examination Reviewer. Subjects handled are Pediatric, Obstetric and Psychiatric Nursing. Previous work experiences include: Clinical instructor/lecturer, clinical coordinator (Level II), caregiver instructor/lecturer, NC2 examination reviewer and staff/clinic nurse. Areas of specialization: Emergency room, Orthopedic Ward and Delivery Room. Also an IELTS passer.

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