Prenatal Development and Influences

Prenatal Development

• Conception involves an ovum (1/175th inch) and sperm (1/500th inch) with 350 million sperm released, 500 reaching the ovum
• Zygote: 1-2 weeks, development of a one-celled zygote into a blastocyst, embedding in the uterine wall, placenta and umbilical cord formation
• Embryo: 3-8 weeks, development of primitive brain and spinal cord, and major internal organs. Growth to 1/2-3 cm, 5g
• Foetus (1st trimester): 9-12 weeks, Organ systems, muscles and organs start connecting. 8 cm, 30g. Starts kicking and sucking thumb, genitals formed
• Foetus (2nd trimester): 13-24 weeks. All neurons form by 24 weeks. 30 cm, 820g. Responds to light and sound.
• Foetus (3rd trimester): 25-38 weeks. Lungs mature, brain grows rapidly, fat added. 50cm, 3.5kg.

Influences on Development

• Drugs: Prescription and illegal drugs (e.g., thalidomide, aspirin, heroin/crack)
• Smoking: Low birth weight and potential behavioural issues
• Alcohol: Fetal alcohol syndrome, cell duplication and migration affected, oxygen deprivation to the foetus
• Maternal illness, poor nutrition, chronic stress: impact on foetal development. Period from 1-2 weeks is generally not susceptible to harmful influences, but the period from 3-8 weeks can have moderate to high risk. Weeks 9-38 have a risk of both moderate and high harmful effects.

Birth Complications

• Preterm and low birth weight: Birth before 3 weeks are considered preterm. <2.5 Kg is low birth weight. These babies are at risk of infection, cognitive impairments, and caregiving problems.
• Birth weight, 3.4-4.7 lb (1,501-2,500g) is associated (7%) with major and (23%) minor disabilities. In birth weight 2.2-3.3 lb (1001-1500g) the risk of major disabilities is 15% and minor disabilities 36%, while for less than 2.2lb (< 1001g) the risk of major disability is 25%, and minor disability is 50%.

Infant Development

Motor Development

• Reflexes: Innate responses to stimuli, vital for survival, mostly disappear after 6 months
• Fine motor skills: Smaller movements like reaching and grasping
• Gross motor skills: Larger movements like crawling, standing, and walking
• Motor milestones (examples): 3-4 months: grasp cube, 7 months: sit alone, 12 months: walk alone
• Cultural variation: Some cultures have earlier infant development patterns.

Perceptual Development

• Touch: Well-developed, including rooting reflex
• Taste: Can distinguish sweet, sour, bitter
• Smell: Prefers familiar scents, especially mother's
• Hearing: Sensitive to complex sounds, prefers speech sounds
• Vision: Least-developed sense at birth, gradual development of depth perception (visual cliff experiments), pattern perception

Memory Development

• Measuring infant memory: Operant conditioning, example: Rovee-Collier (1999) testing infants' memory duration
• Infant memory: highly context specific, infant memory duration differs with age (3 months vs. 6 months).

Explore the stages of prenatal development from conception to the third trimester. Understand the impact of various factors such as drugs, smoking, and alcohol on fetal health and growth. This quiz covers essential concepts of human development during pregnancy.