Lecture 6 - Infant growth and development

Question 1

Define intra-uterine growth

Answer 1

Embryonic and fetal growth (assessed by birthright)

Question 2

Define gestational age

Answer 2

Post-menstrual age. I.e. number of weeks + days since 1st day of last menstrual period

Question 3

What is full term and pre-term?

Answer 3

• Full term: 38-42 weeks post-menstrual age.
• Pre-term: <37 weeks

Question 4

What is a low birthweight?

Answer 4

<2500g at delivery

Question 5

How is newborn growth assessed at delivery?

Answer 5

• Measurement of length, weight, head circumference at delivery
• Assessed using growth charts
• Provides info about patterns of intrauterine growth

Question 6

What can happen in utero when there are adverse circumstances?

Answer 6

• Adaptations may occur in-utero to adverse circumstances
• Increase short-term survival
• Permanent alterations in structure or function occur during “critical periods” of development

Question 7

What are the 3 patterns of intra-uterine growth?

Answer 7

• Small for gestational age (SGA): Weight for age <10th percentile
• Appropriate for gestational age (AGA): Weight for age 10-90th percentile
• Large for gestational age (LGA): weight for age >90th percentile

Question 8

What is essential to know when describing an infants pattern of growth/percentile?

Answer 8

• Need to know gestational age in order to determine what percentile a child is in
• 2000g is low birth weight but 2000g at gestational age of 30 weeks is in the 97% percentile

Question 9

What is birthweight classification and what is the purpose?

Answer 9

• Method of describing likelihood of adverse outcomes (cause for pause to ask for more information)
• Which type of problem depends on birthweight classification and etiology (cause)

Question 10

What three factors can contribute to SGA?

(Etiology of SGA)

Answer 10

• Infant factors: congenital anomalies, genetic conditions, congenital infections
• Placental factors: small placenta, inadequate placental blood flow
• Maternal factors (environmental): smoking, alcohol, drugs, undernutrition

Question 11

What are the risks associated with SGA?

Answer 11

• Hypoglycemia (Not enough glucose from outside of the uterus)
• Inability to maintain temperature (not enough fat)
• Decreased Immune competence (Nutritional status and immune status are closely linked)
• (Neurologic and behavioral problems) - In brackets because it is multifactorial. Hard to discern how much birthweight impacts
• Longer term risks related to in utero adaptations

Question 12

What two factors lead to LGA?

(Etiology of LGA)

Answer 12

-Infant factors: genetic
- Maternal (“environmental”) factors: uncontrolled/poorly controlled diabetes
- Many LGA babies NOT at increased risk, bun infant of diabetic mother (IDM) is at increased risk

Question 13

What are the risks associated with LGA birthweight?

Answer 13

• All: birth injury - For mother and baby
• IDM (Infants of diabetic mothers)
  → Hypoglycemia
  → Hypocalcemia
  → Respiratory, cardiac problems, congenital malformation (3-4 x risk)

Question 14

What is a percentile?

Answer 14

• Proportion of population found below a specific value
• Variability at given age defined by percentiles

Question 15

What is on growth charts (Birth to 2 years)

Answer 15

• Age along x-axis; anthropometric (weight, length, head circumference) measure on y-axis
• Also weight for length: length x-axis; weight measure on y-axis
• Variability at given age defined by percentiles

Question 16

What are the expected growth patterns in infancy?

Answer 16

• Maintenance of growth along “own” percentile (stay within same percentile as they grow)
• Birthweight reflectss prenatal growth factors, postnatal growth dependent on different factors including genetic potential
• Crossing percentiles between 0 and 24 months not uncommon

Question 17

When should you follow up with an infant based on their expected growth pattern and what do you need to consider?

Answer 17

• Flat growth line
• Sharp increase or decrease
• Below 3rd percentile
• Above 97th percentile weight for length
• Consider birthweight, previous growth pattern, gestational age, genetics (e.g. height of parents), type of feeding, presence of a condition/disease

Question 18

What is the expected weight increase for infants?

Answer 18

• Double birth weight by ~4 months
• Triple birthweight by ~1 year

Question 19

How do you assess growth in preterm infants? Give an example

Answer 19

• Preterm <38 weeks gestational age
• Specific pre-term growth chart
• Switch to full term charts when within gestational and measurement ranges using corrected age
• ## E.g. Fenton Growth charts - same concept as other growth charts but uses data starting at 22 weeks gestational age (current age not corrected age)

Question 20

What does corrected age for premature infants mean?

Answer 20

• Corrected age in weeks: current age (weeks since birth) minus (40 weeks - gestational age at birth in weeks)
• E.g. Baby born at 36 wks, current age 24 weeks old
• = 24 - (40-36) = 20 weeks
• Assumes full term to be 40 weeks
• AKA born 4 weeks early so take 4 weeks off their out of womb age
• After 2 years assume infant has caught up to growth and no longer do it

Question 21

What 4 adaptations to post natal life occur?

Answer 21

1. Physiological - gastrointestinal function
2. Protective - mucosal barrier function
3. Biochemical - metabolism
4. Development (mechanical/motor) - feeding (has to learn how to feed)

Question 22

Explain how the gastrointestinal system has developed over time.

Answer 22

• GI tract formed prior to third trimester
• Third trimester: ingestion of amniotic fluid prepares GI tract for nutrients
• GI motility mostly developed; coordination of peristalsis matures early infancy

Question 23

Explain the ability of digestion and absorption in newborns

Answer 23

• At birth able to digest components of breastmilk as efficiently as adults
• Disaccharidases present in near-adult levels; lactate activity increased rapidly with feeding (lactose - disaccharide)
• Pancreatic amylase low; poor starch digestion
• Fat digestion/absorption slightly lower than adult; short and medium chain better absorbed
• Transporters present on brush border

Question 24

How does the disachharidase activity change as we get older?

Answer 24

• by the time of birth, lactase levels are high to break down lactose
• High ability to break down disaccharides. Development begins at age 6 months

Question 25

What is the glomerular filtration rate and how does it change from birth to 3 years?

Answer 25

- **Glomerular filtration rate**: rate at which electrolytes, water, and waste products are transferred from the circulation into the kidney - Birth - 30% adult level - 1 year - 70% adult level - 3 years - 100% adult level - Low rate limits how much they can concentrate their urine. With high amounts of urea would have to excrete more water

Question 26

What is RSL and how does it change?

Answer 26

- Renal solute load - RSL: Electrolytes and urea to be excreted. Increasing RSL requires increases water for excretion - Normal situation: Low RSL - Increased RSL with high protein → Increased water for excretion and/or reduced excretion of wastes

Question 27

What are the protective GI functions present in infancy?

Answer 27

- Development of mucosal gut barrier gradual in infancy - Protective mechanisms in infant gut: → gastric barrier, proteolysis (breakdown of proteins), peristalsis, factors in breastmilk (help lay down immune system in GI) → Mucosal coat and microvillus membrane → Antibodies (IgG, sIgA), other substances

Question 28

What are the major metabolic changes that occur at birth?

Answer 28

- **Major metabolic change at birth is the loss of a constant supply of glucose** - Glycogen and triglyceride synthesis and storage during third trimester → Used during metabolic adaptation at birth - Plasma glucose decreases at birth → reduction in insulin and increase in glucagon (results in glycogen breakdown, lipolysis, gluconeogenesis - use up stores they made in the third trimester)

Question 29

What is the activity and tone of a newborn like?

Answer 29

- **Birth**: initially vigorous and alert 30-60min - **Subsequent**: 80% sleep; 20% active, inactive or crying - **Tone**: Flexion develops from lower to upper limbs 28-40 weeks

Question 30

How are newborns tested?

Answer 30

- APGAR score - Done in delivery room in conjunction wtih birth weight

Question 31

What does APGAR stand for and what does it test?

Answer 31

- Appearance: skin color - Pulse: Heart rate - Grimace: response to stimulation - Activity: flexion (muscle tone) - Respiration: respiratory effort - highest score is 2 for each. Rarely get a 10. Do it right after birth and then 5 minutes later. Depending on score will determine how much help they need

Question 32

What are primitive reflexes?

Answer 32

- Reflect normal nervous system development - Some important for normal feeding behavior at birth - Gradually disappear with maturity (over the first few months)

Question 33

What are the primitive reflexes often tested in new borns?

Answer 33

- **Rooting**: head turning toward stroked face - **Sucking**: reflexive, not voluntary - **Moro**: "startle" reflex - arms move outward, then toward body. Typically cry. Integrate 3-5 months - **Head lag/step**: head movement during pull to sit, stepping movement when held upright. 1-2 months begin to integrate because they gainw eight and cannot support themselves - **Grasping reflex**: more than 4-6 months still there then may have difficulties - **Plantar reflex**: longer than 9 months then may not be able to stand - Go away or integrate when they get older. If they do not need to worry about higher centers of the brain