Infant Terminology and Reflexes

Original Editor - Robin Tacchetti based on the course by Krista Eskay
Top Contributors - Robin Tacchetti, Jess Bell and Naomi O'Reilly

Introduction

Every year, there are an estimated 15 million babies born too early. Babies born before 37 weeks are considered preterm. Depending on the gestational age, preterm can be further divided into three sub-categories:

1. 32-37 weeks: moderate to late preterm
2. 28-32 weeks: very preterm
3. less than 28 weeks: extremely preterm

Complications from preterm birth include death, disability, learning disabilities and visual and hearing problems. Half of the babies born at/or below 32 weeks die in low-resource settings while almost all babies survive in high-income countries. In middle-income settings, suboptimal technology use is increasing the burden of disability for preterm babies who survive.

Often times, preterm births occur spontaneously. The reasons for a preterm birth is may not be determined, but the following list provides some of the known causes:

• infections
• multiple pregnancies
• diabetes
• high blood pressure
• genetics

Low Birth Weight

Babies born weighing less than 2.5 kg are considered low birth weight (LBW) infants. According to the World Health Organization, in a single year 20.5 million live births are considered low birth weight. The majority of these births (91%) are from low and middle-resource countries. Babies born preterm and LBW have a 2-10 times higher risk of mortality. They also have increased risk of complications including:

• respiratory complications
• difficulty feeding
• growth failure
• poor body temperature regulation
• infection
• developmental disabilities (including cerebral palsy)
• long-term adult onset chronic conditions (cardiovascular disease)

** Factors that may affect birth weight include ethnicity, maternal age, maternal health, amount of maternal weight gain in pregnancy, birth order, gestational age, and genetics.

Gestational and Chronological Age

Preterm infants develop and reach milestones at a slower pace than term babies. Premature babies need more time for their body, brain and neurological system to develop. Therefore, preterm infants will have an adjusted age to accommodate for their early birth. The definitions below describe different types of ages:

1. Gestational age: measured in full weeks; first day of the last menstrual period to the day of the birth
2. Chronological age: measured in years, months and days; time elapsed since birth; also referred to as actual age
3. Corrected age: chronological age minus the number of weeks the infant was born before the time when the infant would have reached 40 weeks gestational age; sometimes referred to as adjusted age

** Example: 16-month old toddler who was born at 28 weeks gestation.

• Gestational age: 28 weeks

• Chronological age: 16 months
• Corrected age: chronological age (16 months) - (40 weeks-28 weeks (gestational age))
  • 16 months - (12 weeks)
    • 16 months - (12 weeks = 3 months)
      • 16 months - 3 months = 13 months corrected age

Apgar score

The Apgar score is a quick test performed after birth to report the status of the newborn infant. The test consists of five components:

1. heart rate
2. respiratory effort
3. muscle tone
4. reflex irritability
5. colour

Each factor is given a value from 0-2 with total scores being between 0-10. The Apgar score is performed at 1 and 5 minutes after birth, and it is convenient, accepted and quick.

Primitive Reflexes

Primitive reflexes are involuntary survival-oriented motor responses. These reflexes develop in utero and strengthen postnatally. As the nervous system develops, these reflexes become integrated and diminish during the first three years of life. Since neonates are not capable of cortically directed movements to interact within their environment, primitive reflexes take on that function. The absence or persistence of a reflex could indicate a neurological issue. Delays in primitive reflex integration correlates to reduced sensory processing and delayed milestones. In addition, persistent reflex activity can cause issues with motor skills, coordination, balance, learning difficulties and behavioural problems.

See the table below for a list of primitive reflexes.

Table 1. Primitive reflexes.

Primitive Reflex	Description	Initiated	Integrated
Palmer Grasp	Stroke palm of hand; baby will grip finger	Birth-2 months	4-11 months
Plantar Grasp	Stroke sole of foot; baby will curl toes	Birth	9-12 months
Rooting	Stimulus provided at cheek or lip; infant turns toward it	Prenatal	3 months
Sucking	Root of mouth touched; baby will suck	Prenatal	3 months
Galant	Stroke along paravertebral line, activates trunk flexion towards the stimulus	Prenatal	3 months
Moro	When startled, baby's arms, legs and neck move into extension followed by arms moving together rapidly	Birth	2 months
Babinski	Stroke on foot from heel to toes; big toe moves upward-remaining toes fan out	3-4 months	12-24 months
Parachute	Arms move into extension if they perceive falling (to break the fall)	5-9 months	Persists
Stepping	Holding baby under arm while feet touch surface; baby will simulate walking	Birth	2 months
Flexor Withdrawl	Noxious stimuli to the foot; foot withdraws using hip and knee flexion	Prenatal	1-2 months
Crossed Extension	Noxious stimuli applied to an extended leg; flexion on the stimulus leg with weight shift and extension on the contralateral side	Prenatal	1-2 months
Proprioceptive Placing	Brush the dorsum of the feet against the edge of a surface; will flex up hip and knee and lift foot up to surface then extend leg to accept weight through their leg	Prenatal	2 months
Positive support	Feet on contact surface in a weight-bearing suspension; infant accepts weight through bilateral legs; extension of trunk, hip, knees	Prenatal	1-2 months
Landau	Prone in air supported; head, hips and back should extend	3-4 months	12-24 months

Tonic Reflexes

Tonic reflexes elicit a holding response or cessation of movement. Once placed in a specific position, the infant's muscles will stay contracted and hold that position.

Table 2. Tonic reflexes.

Tonic Reflexes	Description	Initiated	Integrated
Asymmetrical tonic neck reflex (ATNR)	With lateral rotation of the head, extension of the upper and lower extremity on face side, flexion on skull side	Birth-2 months	4-6 months
Tonic labyrinth	In prone, all limbs and head flex; when head is extended, all limbs and head extend	Birth	6 months
Symmetric tonic labyrinth (STNR)	Flexion of the neck causes flexion of the upper extremities and extension of lower extremities; neck extension elicits the opposite	4-6 months	8-12 months

Righting Reactions

Righting reactions are automatic responses to maintain a normal upright posture.

Table 3. Righting reactions.

Righting Reaction	Description
Optic Righting	Using vision to maintain head in a vertical position
Labyrinth	Using inner ear to maintain head in a vertical position when vision is obstructed
Neck Righting	When body is tilted one way, neck maintains head in a vertical position
Vertical Righting	When body is tilted one way, the neck and trunk on the opposite side of the shift will shorten to maintain a vertical position
Rotational Righting	Body on body: flexing either an upper or lower extremity and crossing it over midline to initiate rolling; Head on body: as head rotates the body will follow for rolling

A few of the primitive reflexes are demonstrated in the video below by RegisteredNurseRN:

Resources

• Primitive Reflexes
• Reflexes
• Infant Development