Lecture 6 - Infant growth and development Flashcards
Define intra-uterine growth
Embryonic and fetal growth (assessed by birthright)
Define gestational age
Post-menstrual age. I.e. number of weeks + days since 1st day of last menstrual period
What is full term and pre-term?
- Full term: 38-42 weeks post-menstrual age.
- Pre-term: <37 weeks
What is a low birthweight?
<2500g at delivery
How is newborn growth assessed at delivery?
- Measurement of length, weight, head circumference at delivery
- Assessed using growth charts
- Provides info about patterns of intrauterine growth
What can happen in utero when there are adverse circumstances?
- Adaptations may occur in-utero to adverse circumstances
- Increase short-term survival
- Permanent alterations in structure or function occur during “critical periods” of development
What are the 3 patterns of intra-uterine growth?
- 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
What is essential to know when describing an infants pattern of growth/percentile?
- 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
What is birthweight classification and what is the purpose?
- 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)
What three factors can contribute to SGA?
(Etiology of SGA)
- Infant factors: congenital anomalies, genetic conditions, congenital infections
- Placental factors: small placenta, inadequate placental blood flow
- Maternal factors (environmental): smoking, alcohol, drugs, undernutrition
What are the risks associated with SGA?
- 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
What two factors lead to LGA?
(Etiology of LGA)
-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
What are the risks associated with LGA birthweight?
- All: birth injury - For mother and baby
- IDM (Infants of diabetic mothers)
→ Hypoglycemia
→ Hypocalcemia
→ Respiratory, cardiac problems, congenital malformation (3-4 x risk)
What is a percentile?
- Proportion of population found below a specific value
- Variability at given age defined by percentiles
What is on growth charts (Birth to 2 years)
- 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
What are the expected growth patterns in infancy?
- 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
When should you follow up with an infant based on their expected growth pattern and what do you need to consider?
- 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
What is the expected weight increase for infants?
- Double birth weight by ~4 months
- Triple birthweight by ~1 year
How do you assess growth in preterm infants? Give an example
- 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)
What does corrected age for premature infants mean?
- 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
What 4 adaptations to post natal life occur?
- Physiological - gastrointestinal function
- Protective - mucosal barrier function
- Biochemical - metabolism
- Development (mechanical/motor) - feeding (has to learn how to feed)
Explain how the gastrointestinal system has developed over time.
- 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
Explain the ability of digestion and absorption in newborns
- 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
How does the disachharidase activity change as we get older?
- 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
What is the glomerular filtration rate and how does it change from birth to 3 years?
- 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
What is RSL and how does it change?
- 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
What are the protective GI functions present in infancy?
- 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
What are the major metabolic changes that occur at birth?
- 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)
What is the activity and tone of a newborn like?
- 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
How are newborns tested?
- APGAR score
- Done in delivery room in conjunction wtih birth weight
What does APGAR stand for and what does it test?
- 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
What are primitive reflexes?
- Reflect normal nervous system development
- Some important for normal feeding behavior at birth
- Gradually disappear with maturity (over the first few months)
What are the primitive reflexes often tested in new borns?
- 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
