Child Development: Prenatal, Birth, and Infancy

Chapter 3: Prenatal Development and Birth

Review of Chromosomal Abnormalities (Refresher)
- Trisomies: Presence of three chromosomes instead of the usual pair. Example: Trisomy 21 (Down Syndrome), where there are three chromosomes on the $21$ st chromosome.
- Monosomies: Absence of one chromosome in a pair. Example: On chromosome 23 (sex determination), only one chromosome is present instead of the pair.
- Sex Chromosomal Abnormalities: Conditions arising from an anomalous number of sex chromosomes.
Differences in Prenatal Development (Males vs. Females)
- Males:
  - Testosterone production occurs between weeks $4$ and $8$ . This aids in activity level and sex organ development.
  - Tend to be more physically active.
  - Higher rate of miscarriages.
  - More vulnerable to prenatal problems.
- Females:
  - Development tends to be more advanced than males post-birth until adolescence, then a pivot occurs.
  - Tend to respond more to external stimulation (outside the womb).
  - Have more rapid skeletal development.
Fetal Capabilities and Milestones
- Age of viability: $24$ weeks.
- By $25$ weeks: Infant can recognize the mother's voice.
- By $32$ to $33$ weeks: Infant can recognize different changes within the environment, distinguishing familiar from novel stimuli.
Teratogens (Teratogens): Substances Impacting Development
- Definition: Substances, chemicals, or other agents that can interfere with normal prenatal development.
- Problematic Substances:
  - Drug Use: Can significantly impact development.
  - Alcohol Use: Can lead to Fetal Alcohol Syndrome.
  - Tobacco Use (Cigarettes): Has detrimental effects.
  - Marijuana Use: Can have similar or more severe effects than tobacco, despite different chemicals.
- Other Teratogens and Their Impacts:
  - Cancer: Maternal cancer can be problematic.
  - Chickenpox: Can affect the developing fetus.
  - Sexually Transmitted Diseases (STDs):
    - Rubella exposure: During the first $4$ to $5$ weeks, can cause deafness, cataracts, and heart defects.
    - HIV: Can pass through the placenta or during a vaginal birth. Historically, about one-quarter of exposed infants became infected. However, advancements have made it possible to reduce the mother's viral count to near zero, drastically reducing transmission likelihood.
    - Syphilis, Genital Herpes, Gonorrhea, Chlamydia: Can also affect fetal development.
  - Environmental Substances (Exposures Mothers are Advised to Avoid):
    - Mercury: Often found in contaminated fish.
    - Lead: Found in old pipes and paint.
    - Arsenic: Found in treated lumber.
    - Dental X-rays: Can be damaging to the child if proper precautions aren't taken.
    - Solvents (e.g., paint thinner, rubbing alcohol): Rubbing alcohol, sometimes consumed due to alcoholism, causes severe internal damage.
    - Parasite-Bearing Substances: Animal feces (e.g., cat litter), undercooked meat, poultry, and eggs.
- Overall Impact of Teratogen Exposure: Different parts of the body develop at varying speeds. The timing of exposure is crucial, as a teratogen's impact depends on what specific developmental processes are occurring at that time.
Maternal Malnutrition During Pregnancy
- Impacts of Poor Maternal Diet: Low birth weight, brain stunting, fetal death, and possible mental illness in adulthood (often correlated with environmental factors like poverty).
- Poverty: Identified as the Number One risk factor for various developmental challenges.
- Folic Acid Deficiency: Associated with neural tube defects, affecting the spine and brain. Can lead to conditions like Spinal Bifida, where the spinal cord does not develop properly, resulting in physical deformities.
Maternal Health and Age Concerns
- Maternal Age: Risk factor age for mothers is typically considered $35$ years, though scientific advancements are pushing this higher. Terminology like "geriatric pregnancy" may be used for older mothers.
- Maternal Depression: Can impact fetal development by affecting the mother's self-care, appetite, and energy levels, potentially leading to malnutrition or premature labor. Post-birth, it can contribute to attachment issues with the child.
- Other Maternal Conditions: Diabetes and Lupus can also affect fetal development.
Prenatal Diagnostic Tests
- Purpose: To assess fetal development and identify potential genetic defects or conditions like Trisomy 21.
- Chorionic Villus Sampling ( $chorionic villus sampling$ ): Involves sampling cells from the placenta.
- Amniocentesis ( $amniocentesis$ ): Involves testing the amniotic fluid, typically by tapping into fluid surrounding the fetus.
Birth and Delivery
- Birthing Options: Traditional births, hospital births, home births, or birthing centers, often with the assistance of a midwife.
- Impact of Drugs During Delivery: Infants whose mothers received drugs during labor may be slightly more sluggish and sleep more in the first few weeks, but this difference is generally not noticeable after a few days.
- Three Stages of Delivery:
  1. Stage 1: Contractions begin, and the cervix dilates. Full dilation is when the cervix reaches $10$ centimeters.
  2. Stage 2: The actual delivery of the baby.
  3. Stage 3: Delivery of the placenta and umbilical cord.
Complications and Cesarean Sections (C-sections)
- C-section: A surgical procedure to deliver the baby.
- Reasons for C-section (often planned in advance):
  - Fetal Distress: Signs that the baby is in trouble.
  - Breech Presentation: The baby is positioned feet-first or buttocks-first rather than head-first, which is problematic for vaginal delivery.
  - Birth Size: The baby is too large for a vaginal delivery, or the mother's uterus is not large enough.
  - Poor Progress During Labor: Labor is not advancing as expected.
  - Premature Delivery: If the baby needs to be delivered significantly earlier than term (e.g., at $24$ or $30$ weeks).
  - Mother's Health and/or Age Concerns: Pre-existing maternal conditions or advanced maternal age.
Infant Assessment Tests at Birth
- Apgar Scale: Used to quickly assess the newborn's physical condition after birth.
- Brazelton Neonatal Behavioral Assessment Scale: Measures development over the first two weeks, focusing on responses to stimuli and reflexes.
  - Stimuli: Anything external that elicits a reaction or response (e.g., flickering lights, a scolding).

Chapter 4: Physical Development After Birth

Brain Development in Infancy
- Greatest Developmental Changes: Occur during the first two years of life ( $0-2$ years). The second greatest period of change is during puberty.
- Medulla: Regulates vital functions such as heartbeat, respiration, attention, sleep, waking, elimination, and head/neck movement. It is one of the most fully developed parts of the brain at birth.
- Midbrain: Along with the medulla, it is largely developed at birth.
- Cortex: The least developed part of the brain at birth and continues to develop all the way until approximately $21-23$ years of age.
Synaptic Development and Plasticity
- Synaptic Development: Involves the formation of connections (synapses) between the dendrites of neurons in the brain.
  - Cell Body: The main part of a neuron.
  - Dendrites: Tentacle-like structures that receive signals from other neurons.
  - More environmental exposure and stimulation lead to more synaptic development, while less stimulation leads to less development (demonstrated by research with rats).
- Pruning: A process that occurs after initial synaptic overproduction, fine-tuning the connections by eliminating inefficient or unused synapses.
- Plasticity: The brain's ability to change or adapt in response to experience.
  - The brain initially creates many synaptic connections. Plasticity allows it to become more efficient by getting rid of less-used pathways, optimizing communication (e.g., finding shorter routes for signals).
  - Intellectually challenging environments stimulate the creation of more synapses, promoting greater brain development.
Myelinization
- Myelin: A layer of proteins and fatty substances that wraps around the axons of neurons, forming a myelin sheath.
- Process: Myelinization is the process of myelin forming around neurons.
- Function: It allows for faster and more efficient communication between dendrites by insulating the neural pathways.
- Timing: A significant amount of myelinization occurs during the first two years of life.
Reflexes
- Adaptive Reflexes: Reflexes that aid in survival.
  - Examples: Sucking, withdrawing from pain, opening and closing of pupils.
  - Some, like sucking, are initially automatic but are later replaced by voluntary behaviors. Others, like blinking, remain automatic throughout the lifespan.
- Primitive Reflexes: More complex reflexes that typically disappear ( $not$ be seen after) around $6$ to $8$ months of age.
  - Examples: Babinski reflex (curling of toes when the sole of the foot is stroked) and Moro reflex (a startle reflex involving an outstretching then retracting of limbs).
  - These reflexes are tested to assess for neurological problems. If they persist beyond $6-8$ months, it can indicate issues with neurological development or brain communication.
Sleep Patterns
- Individualized: Sleep patterns vary among infants but tend to stabilize over time.
- Duration: At $6$ months, infants typically sleep about $14$ hours per day.
- Importance: Establishing clear nighttime sleep patterns and daytime napping is crucial, as sleep aids in proper development.
- Cycles: Infants typically move through states of wakefulness and sleep approximately every two hours.
Crying Patterns
- Three Main Types:
  1. Basic Cry: Indicates hunger, a need for attention, or a dirty diaper. Tends to have a rhythmic pattern.
  2. Anger Cry: Louder and more intense than the basic cry.
  3. Pain Cry: Characterized by a very abrupt onset.
- Colic: A distinct pattern involving intense bouts of crying for no apparent reason, lasting for an extended period (e.g., $3$ hours nonstop), and difficult to soothe.
  - Typically resolves after $3$ to $4$ months of age.
Physical Growth
- First Year: Infants grow approximately $10$ to $12$ inches and triple their body weight.
- By Age 2: A child reaches about half of their adult height.
Motor Skills Development
- Infancy: A timeline of motor milestones includes crawling, standing, walking, holding objects, eventually throwing, and feeding oneself.
Bone, Muscle, and Lung Development
- Bone Development:
  - At birth, some bones, like the wrist, are cartilage.
  - By ages $1$ to $3$ years, the wrist separates into bones, eventually consisting of nine different bones by adolescence.
  - Ossification: The process of bones hardening. It is essential for walking, begins in prenatal development, and continues throughout puberty.
- Muscle Development:
  - All muscle fibers are present at birth and develop over time through factors like testosterone, ossification, and exercise.
  - Gender Differences (Childhood & Adolescence): Males typically experience an increase in muscle mass and a decrease in fat ratio, while females tend to experience a decrease in muscle and an increase in fat.
- Gross Motor Skills: Involve large muscle movements (e.g., walking, jumping).
  - Assessed by Physical Therapists.
- Fine Motor Skills (Manipulatives): Involve small, precise movements (e.g., finger dexterity, handwriting).
  - Assessed by Occupational Therapists.
- Lung and Heart Growth: Experience rapid growth during the first two years.
- Stamina: The ability to sustain energy, effort, or activity for an extended period of time. This capacity also develops with physical growth.