Methods of determine gestational age
- Mother’s menstrual history – if accurate, it remains the best measure of gestational age but it depends on normal maternal physiology, accurate and reliable history.
- Prenatal ultrasonography – indirect method, by body part measurement (normal time & proportion of foetal growth rate). Highly accurate when performed in early gestation.
- Postnatal maturational examination (Ballard score estimation)– indirect method, based upon indicators of neuromuscular and physical maturation
Foetal maturation depends on variety of intrauterine experiences.
- Stressful intrauterine experience – accelerate pulmonary, and neuromuscular rate of maturation but slowing foetal growth; Completely non-stress foetus – mature more slowly than average foetus
- With accelerate foetal maturation à slowing foetal growth
- With accelerate foetal growth à delay foetal maturation
Active and passive muscle tone
Muscle tone = slight constant tension of healthy muscles which contributes to a slight resistance to the passive displacement of a limb
- Active muscle tone
– assess motility, activity, efforts at righting oneself
– affected by state of illness, recent maternal medication, acute perinatal compromise, level of alertness
– therefore NOT CONSISTENTLY USEFUL to evaluate baseline neuromuscular maturity
- Passive muscle tone – useful for evaluating maturational development of neonatal brain, regardless of infant’s state of alertness or level of wellness
– Extensor tone
– Flexor tone
- Foetus lying primarily with limb extended in very early phase of development; gradually it assumes the progressive flex attitude.
- This is true whether the development occurs in nursery or in utero, suggesting that flexion results from the maturation of CNS rather than compressive forces in uterus, i.e. flexion overcomes extension as maturation progresses.
Development of neuromuscular tone progresses in a caudocephalic and centripedal direction, i.e. lower extremities developed slightly ahead than upper extremities’ tone.
Assessing flexor tone
1. Extensor stretch or passive flexion
- Flexibility – degree of join can be flex – wrist angle (square window)
2. Resistance to passive extension
i. Rest on supporting surface (untested part of extremities)
ii. Be sensitive to slight tendency to resist extension
iii. Support thigh from sides
iv. Avoid placing pressure/ touching flexor muscles
3. Measuring the angles of recoil (to previously flexed position)
i. Support upper arm
ii. Preset extremities in flexion
iii. Extend only momentarily
iv. Avoid fatiguing flexors – not to remain in extended position in too long time
New Ballard Score
- Ballard score estimation is indicated for all preterm infant (<37 weeks of gestation) or term infant clinically large/small.
- Consists of 2 parts: (a) neuromuscular maturity (b) physical maturity
- Score is estimated in unit “week”.
Infant is placed supine, examiner wait until the infant settles to a relaxed & preferred position.
Examiner straightens the infant’s fingers and applies gentle pressure on dorsum of hand.
Examiner places his one hand beneath the infant’s elbow for support. Taking the infant’s hand, examiner quickly sets the elbow in flexion, and then momentarily extends the arm before release the hand. The angle of recoil is noted.
Remember to avoid fatiguing flexors!
Thigh place in infant’s abdomen with knee fully flexed, examiner gently grasp foot at side by one hand while supporting the thigh by others. Care not to exert pressure to the hamstring muscle, as it might interfere with their function. Leg is extended until a definite resistance to extension is appreciated.
If prenatally it is in flexed breech presentation might interfere this manoeuvre within 24-48 hrs of life, due to prolonged flexor fatigue. The test should be repeated once recovery had occurred.
Examiner with one hand support the infant’s head in midline and infant hand just above the chest
The thumb of examiner other hand is placed on the elbow. The examiner nudges the elbow across the chest, feeling for resistance to extension of the flexor muscle about the shoulder girdle.
Hell to ear
Lower extremities flexed at hip so that it rests on the mattress alongside of infant’s trunk. Examiner holds the infant’s thigh alongside the body with the palm of the hand avoiding pressure on hamstring; the other hand is used to grasp the sides of heel toward the ipsilateral ear. Using the infant’s heel as an indicator, examiner feels the resistance to extension of the pelvic girdle flexors by noting the point of the body where significant resistance is appreciated.