Moro reflex Anthropometry Upper limb : lower limb ratio Scarf sign gradings and it's interpretations Explain in detail for practices pedatrics
Reading File
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Searching PubMed
newborn anthropometry AND assessment
Searching the Web
Moro reflex anthropometry scarf sign gestational age assessment upper lower segment ratio pediatrics
Reading File
Finding Sources
Finding Sources
Reading Web Page
https://www.ncbi.nlm.nih.gov/books/NBK542173
Reading File
Finding Sources
Finding Sources
1. Moro reflex
The Moro reflex is a primitive neonatal reflex, also called the startle reflex.
Age
- Present at birth in term infants.
- May be weak or incomplete in very preterm infants.
- Begins to diminish by about 3-4 months.
- Normally disappears by 5-6 months.
Persistence beyond 6 months needs developmental assessment, especially for upper motor neuron dysfunction or spastic cerebral palsy. A useful current review is available in the NCBI Moro reflex chapter.
How to elicit it correctly
- Ensure the baby is calm, warm, and lying supine.
- Support the head and upper trunk with one hand.
- Produce a brief, sudden sensation of loss of support by allowing the head/trunk to drop a few centimetres into your supporting hand.
- Do not actually let the head fall or use a painful stimulus.
Normal response
It has two phases:
-
First phase
- Symmetrical abduction of both arms
- Extension at shoulders and elbows
- Extension and opening of fingers
-
Second phase
- Arms come back toward the midline, with flexion/adduction
- Often followed by crying
Interpretation
| Finding | Important possibilities |
|---|---|
| Symmetric, brisk response | Normal in a newborn/young infant |
| Absent bilaterally | Severe CNS depression, severe hypoxia/asphyxia, intracranial hemorrhage, major neuromuscular weakness, profound sedation, severe illness |
| Weak response | Prematurity, hypotonia, illness, sedative exposure, neuromuscular weakness |
| Asymmetric Moro | Clavicle fracture, humerus fracture, brachial plexus palsy, painful shoulder/arm injury, hemiplegia |
| Exaggerated response | Jitteriness, hypoglycaemia, drug withdrawal, hyperekplexia, increased CNS irritability |
| Persists after 6 months | Consider cerebral palsy or other neurological abnormality |
Practical point
In a baby with asymmetric Moro, first inspect and palpate both clavicles and upper limbs, assess spontaneous movements, and check grasp reflex. A clavicle fracture and Erb palsy are common practical differentials.
2. Anthropometry in paediatrics
Anthropometry means systematic measurement of body size and proportions. It is used to assess:
- Growth and nutritional status
- Acute and chronic malnutrition
- Obesity
- Proportionate versus disproportionate short stature
- Microcephaly or macrocephaly
- Fetal growth status in newborns
- Response to nutritional or medical treatment
Plot serial measurements on an appropriate WHO or national age- and sex-specific growth chart. A single measurement is less informative than the growth trend.
Core measurements
| Measurement | Main use | Method |
|---|---|---|
| Weight | Nutritional status; growth monitoring | Minimal clothing, calibrated scale |
| Length | Children under 2 years | Recumbent length board, two trained persons ideally |
| Standing height | Usually age 2 years and above | Stadiometer, heels together, head in Frankfurt plane |
| Head circumference | Brain growth | Non-stretchable tape around maximum occipito-frontal circumference |
| Mid-upper arm circumference (MUAC) | Acute malnutrition in 6-59 months | Measure midpoint between acromion and olecranon on left arm |
| BMI | Overweight/obesity, thinness in older children | Weight (kg) / height (m²), then plot BMI-for-age |
| Chest circumference | Less commonly used; neonatal assessment | At nipple level, at end expiration |
| Upper segment:lower segment ratio | Body proportion and skeletal/endocrine disorders | See below |
| Arm span | Proportionality and tall stature | Middle fingertip to middle fingertip with arms abducted to 90° |
Key practical rules
- Use a calibrated instrument.
- Record to appropriate precision:
- Weight: nearest 10-100 g depending on age/scale
- Length/height: nearest 0.1 cm
- Head circumference and MUAC: nearest 0.1 cm
- Measure twice if the child is restless or the result seems unexpected.
- Always interpret against age, sex, gestational age in newborns, and the child’s previous growth trajectory.
Nutritional interpretation
Weight-for-age
- Detects underweight but cannot distinguish wasting from stunting.
Height-for-age
- Low height-for-age suggests stunting, generally reflecting chronic undernutrition, chronic disease, or a growth disorder.
Weight-for-height/length or BMI-for-age
- Low value suggests wasting or acute malnutrition.
- High value suggests overweight/obesity.
MUAC
For children aged 6-59 months:
- MUAC <11.5 cm: severe acute malnutrition, especially if compatible clinically
- 11.5 to <12.5 cm: moderate acute malnutrition/risk category depending on programme criteria
- Bilateral pitting nutritional oedema is also a marker of severe acute malnutrition.
Park’s Textbook defines severe acute malnutrition as weight-for-height/length below -3 SD, MUAC below 115 mm, or nutritional oedema.
Park’s Textbook of Preventive and Social Medicine, section on Severe Acute Malnutrition.
Park’s Textbook of Preventive and Social Medicine, section on Severe Acute Malnutrition.
3. Upper segment:lower segment ratio
Definitions
- Lower segment (LS): distance from the upper border of symphysis pubis to the floor, measured standing.
- Upper segment (US):
[
\text{Upper segment} = \text{Total height} - \text{Lower segment}
]
- US:LS ratio:
[
\text{US:LS ratio} = \frac{\text{Upper segment}}{\text{Lower segment}}
]
How to measure in practice
- Measure standing height with a stadiometer.
- Ask the child to stand straight with feet together.
- Measure from the upper border of symphysis pubis to the floor.
- Calculate upper segment as height minus lower segment.
- Calculate the ratio.
Example
- Height = 120 cm
- Lower segment = 65 cm
- Upper segment = 120 - 65 = 55 cm
[
US:LS = \frac{55}{65} = 0.85
]
Approximate normal values
| Age | Approximate US:LS ratio |
|---|---|
| Birth | 1.7:1 |
| 1 year | 1.5:1 |
| 3 years | 1.3:1 |
| 7 years | 1:1 |
| Adult | 0.85-0.9:1 |
The ratio declines with age because legs grow faster than the trunk during childhood.
Interpretation
| Ratio pattern | Meaning | Examples |
|---|---|---|
| Increased US:LS ratio | Relatively short lower limbs | Achondroplasia and other skeletal dysplasias, rickets, hypothyroidism, some mucopolysaccharidoses |
| Decreased US:LS ratio | Relatively long lower limbs | Marfan syndrome, homocystinuria, Klinefelter syndrome, some children with precocious puberty |
| Normal ratio with short stature | Proportionate short stature | Familial short stature, constitutional delay, chronic systemic disease, growth hormone deficiency |
Relation with arm span
- In older children, arm span is approximately equal to height.
- Arm span greater than height and a reduced US:LS ratio suggest a marfanoid body habitus.
- In disproportionate dwarfism, arm span and limb proportions may be markedly abnormal.
4. Scarf sign
The scarf sign is a neuromuscular maturity assessment used in the New Ballard score for estimation of gestational age. It assesses passive flexor tone around the shoulder girdle.
The Ballard score is particularly useful when a reliable menstrual history or early antenatal ultrasound is unavailable. It is most reliable when performed around 24 hours after birth.
The Harriet Lane Handbook, 23rd ed., pp. 644-646.
The Harriet Lane Handbook, 23rd ed., pp. 644-646.
How to perform
- Lay the baby supine and keep the shoulders flat on the examination surface.
- Hold one hand of the baby.
- Gently draw that arm across the upper chest and neck, as if placing a scarf around the neck.
- Observe where the elbow lies in relation to the chest.
- Do not force the arm. The baby should be relaxed.
Principle
- Preterm babies have reduced flexor tone and less resistance to passive movement. Their elbow crosses far over the chest.
- Term/post-term babies have higher flexor tone and more resistance. Their elbow does not cross the midline easily.
Therefore:
More crossing of the elbow = lower score = greater prematurity
Less crossing of the elbow = higher score = greater maturity
Scarf sign grading
| Score | Elbow position after drawing arm across chest | Interpretation |
|---|---|---|
| 0 | Elbow reaches the opposite axillary line | Very low shoulder tone, more premature infant |
| 1 | Elbow passes the opposite mid-axillary line but still crosses substantially | Preterm pattern |
| 2 | Elbow reaches or is around the midline of the chest | More mature infant |
| 3 | Elbow cannot reach the midline | Greater flexor tone, term or post-term pattern |
The Harriet Lane Handbook describes: score 0 when the elbow reaches the opposite axillary line, 1 when it passes the mid-axillary line, 2 when it passes the midline, and 3 when it cannot reach the midline. Use the exact locally adopted New Ballard chart when assigning the final score, because illustrated charts may include additional negative or higher categories.
Interpretation in words
Very preterm infant
- Arm moves easily across chest
- Elbow may reach or cross the opposite axillary region
- Low score
Term infant
- Moderate resistance
- Elbow generally reaches only around the midline
- Intermediate-to-high score
Post-term infant
- Marked resistance to passive movement
- Elbow stays well short of midline
- High score
Common errors
- Testing when the baby is crying or actively resisting
- Pulling too forcefully
- Allowing the shoulder/scapula to lift off the bed
- Using scarf sign alone to date gestation
- Ignoring factors that alter tone, such as birth asphyxia, sepsis, sedation, hypothermia, neuromuscular disease, or maternal magnesium sulphate exposure
Scarf sign should be combined with other Ballard neuromuscular signs:
- Posture
- Square window
- Arm recoil
- Popliteal angle
- Heel-to-ear maneuver
and physical maturity signs:
- Skin
- Lanugo
- Plantar creases
- Breast tissue
- Eye/ear features
- Genitalia.
Exam-style summary
- Moro reflex: present at birth, disappears by 5-6 months; asymmetry suggests clavicle fracture or brachial plexus injury.
- Anthropometry: weight, length/height, head circumference, MUAC, BMI, body proportions; always plot serially on growth charts.
- US:LS ratio: 1.7 at birth, 1 at 7 years; high ratio means short legs, low ratio means long legs.
- Scarf sign: part of New Ballard assessment; greater elbow crossing indicates prematurity, while increased resistance indicates maturity.
This is a shared conversation. Sign in to Orris to start your own chat.