Prenatal Development and Atypical Growth

Prenatal Development

• Hormonal Influence: Male embryos secrete testosterone from the second month, unlike female fetuses. Prenatal hormones significantly impact brain development and functioning throughout life.
• Skeletal Development: Girls experience faster skeletal development prenatally, but boys are typically born taller and heavier.
• Sex Ratio and Prenatal Vulnerability: More males are conceived, but more are spontaneously aborted. Male fetuses are more vulnerable to external stressors and congenital problems while in utero and throughout life, potentially facing earlier death and increased risk of behavioral/learning difficulties.

Atypical Prenatal Development

• Genetic Disorders:

• Autosomal: Occur in the first 22 chromosome pairs and can be caused by recessive or dominant genes. Examples include PKU, sickle cell anemia, Tay-Sachs (visual impairment), and Huntington's disease.

• Sex-Linked: Found on the 23rd chromosome pair, mostly due to recessive genes. Examples include red-green color blindness, hemophilia, and fragile X syndrome (mild to moderate learning disabilities, autistic features, social anxiety, and specific physical characteristics).

• Chromosomal Anomalies:

• Trisomies: An extra copy of an autosome, like Down Syndrome.

• Sex Chromosome Anomalies: Incomplete or incorrect division of sex chromosomes. Examples include Klinefelter's syndrome (XXY - male characteristics with some female traits) and Turner's syndrome (XO - female characteristics with some abnormalities).

• Teratogens:

• Prenatal development can be impacted by environmental factors. Key susceptibility periods are usually in the first trimester.

• Examples of teratogens: Maternal diseases (rubella, HIV, cytomegalovirus, STDs), substance abuse (smoking, alcohol, cocaine, heroin, marijuana), vitamin deficiency, environmental hazards, chemicals, and maternal diet.

Birth and Early Infancy

• Stages of Labor:

• Dilation and Effacement: Cervical opening and thinning. This stage can take 8-12 hours, longer in first births or with anesthesia.

• Delivery: Full cervical dilation, pushing stage - 20-50 minutes.

• Afterbirth: Delivery of the placenta and uterine material.

• Newborn Assessment (APGAR):

• Appearance (color): Crucial indicator of health.

• Pulse: Heart rate.

• Grimace (reflexes): Response to stimulation.

• Activity (muscle tone): Muscle strength.

• Respiration: Breathing and crying. Babies with syndromes are frequently flaccid.

• Infant Reflexes:

• Adaptive Reflexes: Essential for survival in newborns, but disappear in the first year (swallowing, rooting reflexes).

• Primitive Reflexes: Not essential for survival, also disappear in the first year (Moro reflex). Potentially linked to later behavior patterns.

• Infant States of Consciousness: Neonates display 5 states, recurring every 2 hours: deep sleep, active sleep, quiet awake, active awake, crying and fussing.

• Crying: A significant part of the newborn's behavior pattern. Crying can denote various needs.

Physical and Cognitive Abilities

• Motor Development: Proceeds in a cephalocaudal (head-downwards) and proximodistal (trunk-outwards) direction. Initial movements may not be fully voluntary or coordinated.

• Perceptual Skills: More developed than motor skills in newborns.

• Vision: Focussing, distinguishing faces, and tracking movement..

• Hearing: Discriminating pitch and loudness, locating sounds.

• Taste and Smell: Recognizing tastes and odors.

• Learning:

• Classical conditioning: Learning by association (ex. sugar water).

• Operant conditioning: Learning through reinforcement (ex. head turning).

• Schematic learning: Organising experiences into expectations; distinguishing between novel and familiar events.

• Habituation: Responding less strongly to repeated stimulation.

Temperament and Social Skills

• Temperament: Innate personality traits, including reactions to new situations, moods, activity levels, and social preferences. Easy, difficult, and slow-to-warm-up categories exist.
• Early Emotions: Interest, distress, disgust, and a half-smile emerge in the first months. Later emotions include anger, joy, fear, and surprise. Imitation may start.
• Infant needs for health: Adequate nutrition and healthcare are mandatory for a baby's well-being.

Illnesses in Infancy

• Diarrhea: A major cause of infant mortality.
• Respiratory and Ear Infections: Common among infants.

Physical Development: Brain and Nervous System

• Brain Structures: Midbrain, cerebellum, cortex, spinal cord, and medulla.

• Brain Development: The cortex is less developed at birth but crucial for higher-level functions. Development involves growth spurts, synaptic development, myelination, and lateralization (specialization of brain hemispheres).

• Neuroplasticity: The potential for brain change throughout life, depending on experience.

• Myelination: Insulation of axons, critical for advanced mental abilities, such as attention.

• Lateralization: Hemispheric specialization in brain function (left-brain dominant in most people).

Bones, Muscles, and Motor Skills

• Physical Changes: Growth phases and differences in rate and patterns (cephalocaudal, proximodistal).
• Bones: Bone development differs between sexes, with fusion of fontanels at 18 months.
• Muscle and Fat: Muscle and fat tissue undergo changes, leading to differences in strength and body composition linked to sex hormones.
• Motor Development: Includes gross (movement) and fine (manipulation) motor skills.

Sexual Maturation

• Hormonal Role: Endocrine glands, particularly the pituitary gland, regulate growth and sexual maturation.
• Sequence of Puberty: Both boys and girls go through different changes sequentially.
• Timing of Puberty: Early development can be associated with various adjustment challenges in both sexes.