Development Across the Lifespan: Week 4a - Birth and Infancy

Birth

Birth Choices

• There are four primary locations for birth:

  • Traditional hospital maternity unit: Accounts for approximately $97.8\%$ of births.

  • Hospital-based birth center or birthing room.

  • Free-standing birth center.

  • Home delivery.

• Midwives are regulated health professionals in most parts of Canada.

• Three common types of drugs used during labor and delivery include:

  • Analgesics.

  • Sedatives or tranquilizers.

  • Anesthesia (e.g., epidural).

The Physical Birth Process

• Stage 1: Involves two critical processes:

  • Dilation: The cervix opens to about $10\text{ cm}$ to allow the baby to pass through.

  • Effacement: The flattening of the cervix.

• Stage 2: The actual delivery of the baby, occurring once the cervix is fully dilated.

• Stage 3: The afterbirth, which is the delivery of the placenta and other maternal material from the uterus.

• Most infants are delivered head first, facing toward the mother's spine.

• Breech birth: Occurs when the baby is oriented differently, either feet first or bottom first.

• After birth, most women require a recovery period of approximately one month.

• Typically, medical follow-up is scheduled $6\text{-weeks}$ post-partum.

Birth Complications

• Fetal distress: Characterized by a sudden change in the baby's heart rate.

• Anoxia: Oxygen deprivation, which can lead to death or brain damage (e.g., cerebral palsy).

• Dislocation, fractures, and nerve damage.

Assessing the Neonate

• Neonate: Refers to a baby between birth and $1\text{ month}$ of age.

• The health of neonates is commonly assessed using the Apgar scale.

• Standard screening is performed for rare metabolic disorders.

• Brazelton Neonatal Behavioral Assessment Scale: Used to track a newborn's development over the first approximately $2\text{ weeks}$ after birth to identify significant neurological disorders.

The Apgar Scale

Low Birth Weight (LBW)

• Low birth weight (LBW): Defined as a newborn weight below $2500\text{ grams}$.

• Preterm: Infants born before the $38^{\text{th}}$ week of gestation; this category includes most LBW babies.

• Small-for-date: Full-term infants weighing less than $2500\text{ grams}$.

• Infants weighing below $1500\text{ grams}$ show significantly higher rates of long-term problems, including lower intelligence test scores, smaller size, and more schooling issues.

• Boys are at a greater risk than girls to exhibit long-term effects of LBW.

Physical Development in Infancy

General Physical Development

• The greatest degree of physical change (excluding prenatal development) occurs during infancy, which spans the first $2\text{ years}$ of life.

• Babies typically grow $25\text{-}30\text{ cm}$ and triple their body weight in the first year.

• By about age $2$ (girls) and age $2\frac{1}{2}$ (boys), toddlers are half as tall as they will be as adults.

• $2\text{-year-olds}'$ heads are proportionately much larger than adults' heads; this is necessary to accommodate their nearly full-sized brains.

Brain & Nervous System

• The brain and nervous system undergo rapid development during the first two years.

• Midbrain and Medulla: Regulate vital functions and are the most fully developed parts of the brain at birth.

• Cortex: Involved in perception, body movement, thinking, and language. It is the least developed part of the brain at birth.

Synaptic Development

• Synaptogenesis: The process of creating synapses.

• This is followed by a period of synaptic pruning, which makes the brain more efficient by eliminating unused synapses.

• Neuroplasticity: The brain's capacity to reorganize neural pathways and connections based on experience.

• A $1\text{-year-old's}$ brain has denser dendrites and synapses than an adult's, but the $1\text{-year-old's}$ neural network operates far less efficiently.

Myelinization

• Myelin: A substance that gradually covers individual axons, electrically insulating them from one another and improving nerve conductivity.

• Myelinization is most rapid during the first two years after birth and continues throughout childhood and adolescence.

• Reticular Formation: A part of the brain that regulates attention; it isn't fully myelinated until the mid-$20\text{s}$.

Reflexes

• Adaptive reflexes: Essential for newborn survival, such as sucking. Some disappear in infancy or childhood, while others persist for life.

• Primitive reflexes: Controlled by primitive parts of the brain and typically disappear by about $6\text{ months}$ of age.

Examples of Adaptive Reflexes

• Rooting: A soft touch on the cheek causes an infant to turn toward the touch and open their mouth to suck. This reflex disappears by $3\text{ months}$.

• Babinski: When the sole of the foot is stroked, the infant’s toes fan out and up. This reflex disappears around $12\text{ months}$.

• Moro: A sudden noise or loss of support causes the infant to arch their back, throw their arms and legs out, and then bring them back in. This reflex disappears after $4$ or $5\text{ months}$.

Behavioral States

• Infants typically cycle through five different states of consciousness in a consistent sequence.

• Patterns of sleep and wakefulness stabilize with age.

• Neonates sleep about $80\%$ of the time.

• By $8\text{ weeks}$, babies often begin to sleep through the night.

• By $6\text{ months}$, babies are sleeping around $13\text{ hours/day}$, with clear nighttime sleep patterns and established daytime naps.

• Cultural beliefs significantly influence parents' responses to infants' sleep patterns.

Cries

• Basic cry: Signals hunger and follows a rhythmical pattern.

• Anger cry: Louder and more intense than a basic cry.

• Pain cry: Characterized by a very abrupt onset.

• Cross-cultural studies suggest that crying increases until $6\text{ weeks}$ of age and then gradually decreases.

• Prompt attention to crying in the first three months is associated with less crying later on.

• Colic: An infant behavioral pattern of unknown cause, involving intense daily bouts of crying, totaling three or more hours a day for several months.

Body Systems & Motor Skills

• The acquisition of motor skills depends on brain development and substantial changes in other body systems.

• Physical development follows two patterns:

  • Cephalocaudal pattern: Development proceeds from the head downward.

  • Proximodistal pattern: Development proceeds from the center of the body outward.

Bones

• Changes in bone length contribute to height.

• Changes in the amount and density of bones are crucial for improved coordination.

• Ossification: The process of hardening of bones, which begins during prenatal development and continues through puberty. It is essential for motor development.

Muscles

• Virtually all muscle fibers are present at birth.

• Initially, muscle fibers are small and have a high ratio of water to muscle.

• High fat content in muscles declines to adult levels by age $1$.

Lungs and Heart

• Improvements in lung efficiency and increasing strength of heart muscles contribute to a $2\text{-year-old's}$ greater stamina compared to a newborn.

Types of Motor Skills

• Motor skills are generally divided into three groups:

  • Locomotor skills (gross motor): Involve large muscle movements, e.g., crawling.

  • Nonlocomotor skills: Involve controlling body parts without moving the whole body, e.g., head movements.

  • Manipulative skills (fine motor): Involve small muscle movements, e.g., using fingers.

• There is wide variability in the ages at which infants reach developmental milestones, both within and between cultural settings.

  • For example, Indigenous children generally achieve gross motor skills earlier but language skills slightly later compared to broader Canadian norms.

Motor Development Milestones (Selected Examples)

• 1 month: Lifts head slightly, holds objects if placed in hand.

• 2-3 months: Lifts head up to $90\text{-degree}$ angle on stomach, begins to swipe at objects.

• 4-6 months: Rolls over, sits with support, creeps on hands and knees, reaches for and grasps objects.

• 7-9 months: Sits without support, crawls, transfers objects from one hand to the other.

• 10-12 months: Pulls self up, walks grasping furniture, then walks alone; shows some signs of hand preference.

• 13-18 months: Walks backward, sideways, runs; stacks two blocks, puts objects into small containers.

• 19-24 months: Walks up and down stairs (two feet/step), jumps with both feet off the ground; uses a spoon to feed self, stacks $4\text{-}10$ blocks.

Gender Differences in Motor Skills

• Girls show an advantage in some aspects of physical maturity during infancy, with a slight edge in manipulative skills.

• Boys are typically more active and exhibit a clear preference for rough-and-tumble play.

• Boys are generally more aggressive than girls by the end of the second year.

Explaining Motor Skill Development

• Virtually all children follow the same sequence of motor skill development.

• Developmentally delayed children simply progress through these stages more slowly.

• Maturation plays a significant role in motor development.

• Experience in normal environments influences motor development outcomes.

Health Promotion and Wellness

Nutrition

• Maternal lifestyle, breastfeeding practices, environmental factors, and potentially ethnicity can influence the quality of breast milk.

• Breast milk is nutritionally superior to formula:

  • Contributes to more rapid weight gain and size.

  • Babies are less likely to suffer from common illnesses.

  • Stimulates better immune system functioning.

• Preterm babies often require supplements to augment breast milk.

• Maternal medications or the mother's health conditions may make breastfeeding impossible.

• At $6\text{ months}$, healthy, full-term infants are generally ready for the introduction of solid foods.

Malnutrition

• Malnutrition in infancy can severely impair brain development.

• Macronutrient malnutrition: A diet with too few calories.

  • This is the leading cause of death in children under $5$.

  • Marasmus: Caused by severe calorie deficiency, leading to extremely small infants who may suffer permanent brain damage.

  • Kwashiorkor: A diet too low in protein, resulting in chronically ill children with high water retention in the belly.

• Micronutrient malnutrition: Deficiency of certain vitamins or minerals.

  • This is the most common form of malnutrition in industrialized countries, though Canada is an exception due to widespread food fortification over the past $60\text{ years}$.

  • Mortality can be reduced by $23\%$ by providing young children with Vitamin A.

Health Care and Immunizations

• Infants require frequent medical check-ups.

• Routine immunization should commence at $2\text{ months}$ of age and continue throughout childhood and adolescence.

• A complete set of immunizations typically includes:

  • Chickenpox

  • Hepatitis

  • Diphtheria/tetanus/pertussis (DTaP)

  • Influenza

  • Polio

  • Pneumonia

  • Meningitis

  • Measles, mumps, and rubella (MMR) virus vaccine.

Illnesses in the First Two Years

• Over half of infants in Canada experience a respiratory illness in their first year of life.

• Babies in daycares have approximately twice as many infections as those cared for exclusively at home; those in small-group daycare fall somewhere in between.

• Infants with chronic ear infections are more prone to developing learning disabilities, attention disorders, and language deficits during their school years compared to their peers.

Preterm and Low Birth Weight (LBW) Infants

• Preterm infants: Those born before $37\text{-}38\text{ weeks}$ of gestation.

• Infants born before $32\text{ weeks}$ of gestation may lack adaptive reflexes.

• Many preterm infants require intravenous feeding or feeding through a tube inserted into the esophagus or stomach.

• Infants born preterm or with LBW often progress more slowly through developmental milestones.

• By age $2$ or $3$, physically normal preterm babies typically catch up with their peers.

• Kangaroo care (skin-to-skin contact) can be beneficial for the care of preterm newborns.

Post-term Infants

• Infants born $42\text{ weeks}$ or more after conception are categorized as post-term.

• Post-term babies face an increased risk of fetal and neonatal mortality.

• Ultrasound dating and the practice of inducing post-term pregnancies have led to a decrease in the rate of post-term deliveries in Canada.

Infant Mortality in Canada

• Roughly half of infant deaths in Canada occur during the neonatal period (first $28\text{ days}$), with the remainder occurring between $4\text{ weeks}$ and $1\text{ year}$ of age.

• Infant Mortality Rate: The death of an infant within the first year of life.

• Canada's infant mortality rate has significantly declined from $134$ per $1000\text{ live births}$ in $1901$ to approximately $5$ per $1000\text{ live births}$ in $2007$.

• Lower-income families and families in remote areas experience higher infant mortality rates.

• Inuit, First Nations, and Métis populations have infant mortality rates that are $3.9$, $2.3$, and $1.9$ times higher, respectively, than the general Canadian population.

Sudden Infant Death Syndrome (SIDS)

• SIDS: The sudden, unexpected death of an apparently healthy infant (accounts for about $5\%$ of all infant deaths in Canada).

• $90\%$ of SIDS cases occur between $28\text{ days}$ and $1\text{ year}$ of age.

• To reduce the risk of SIDS:

  • Place the baby on their back for all sleeping periods.

  • Remove quilts, duvets, pillows, soft toys, and crib bumpers that could cover the infant's head.

  • Avoid placing the baby on soft surfaces or loose bedding.

  • Have the baby sleep near the parent's bed for the first $6\text{ months}$.

  • Avoid bed-sharing or otherwise sleeping/napping with the baby.

  • Ensure a smoke-free environment during pregnancy and in the home after the infant's birth.