Stages of Prenatal Development
Germinal Stage: 2 weeks post conception
Embryonic Stage: Up to 2 months after conception
- Major organs form
Fetal Stage: 2 months - Birth
- 3 months: Sex organs form
- Brain grows rapidly, insulating layer of fat forms under skin, resipratory and digestive systems start to work independently
Prenatal Brain Development
5-20 Weeks: Neurons generate at a rate of 250,000 per minute
- Majority between embryonic days 41-125
7 Months Onwards: Only physical changed relate to:
- Increase in fat tissue (including white matter)
- Increase in muscle size and strength
- Regulatory systems (temperature and breating regulation, etc.)
Development of Sensory Systems
Fetal Taste
Maternal food alters the ‘flavour’ of amniotoc fluid
Sensitivities to sweet over other tastes prenatally
- Poor at detecting salty tastes even after birth
Development of Sensory Systems
Fetal Hearing
6 Weeks: Initial structure of inner ear formed
7 Weeks: Auditory canal begins to develop
- Links inner ear to the brain
10 Weeks: Sensory cells develop along canals
20 Weeks: Improvements in the system
- Third bone of the ear develops and structure hardens
- Reliable response to sound
24 Weeks: Fully functional system
- 16 weeks left of pregnancy: What does infant hear/experience?
Development of Sensory Systems
Fetal Vision
8-22 Weeks: Eyelids sealed
9 Weeks: Optic nerve formed
- Connects eye to brain
12-28 Weeks: Retinal layering
- Detect movement, colour, shape, sizes, etc.
- Develops from peripheral to foveal
28 Weeks Onward: Bright light sone on uterus causes an increase in fetal heart rate
Development of Sensory Systems
Fetal Sensation of Motion
5 Months: Sense of balance
- Evidence from rocking studies and fetal counterbalance of position behaviours
- Suggests key aspect of vestibular system is intact at this age (Linked to auditory development)
- Relies on the development of inner ear
Development of Sensory Systems
Organised Embryonic Behaviours
8 Weeks: Sensitivities in feet, hands, and mouth
- Nerves around body do not develop universally all at once
- Sensory feedback/experience (Habituate to it)
8-12 Weeks: Kicking feet, bending arms, sucking thumbs, expand and contract lungs, etc.
Organised Embryonic Behaviours
Hepper et al. (2005)
Even handedness might be developed in utero
- All 60 right handed fetuses were right handed postnatally
- 10/15 left handed fetuses were left handed postnatally: Most likely taught by right handed people so moved across to right handedness
Reissland et al. (2013)
Mapping movements longitudinally (24-36 weeks)
- Reactive movements = Touched mouth then opened mouth
- Anticipatory movements = Opened mouth before hand touched
- 25 Weeks: Reactive movements start to decrease and anticipatory increase
- 34 Weeks Onwards: Increasingly more anticipatory movements than reactive
Teratogens
Any substance that may interfere with the development of the fetus
Teratogens
Fetal Alcohol Syndrome
- Affects 1 in 1,000 live births
- Distinctive facial structure
- Restricted growth
- Intellectual impairments
- Early intervention can show improvement
Teratogens: Alcohol
How does alcohol affect brain development?
Theory A: Ethanol blocks receptors from receiving neurochemicals and thus communication between neurons
- Cannot set up systems in the brain as easily
Theory B: Ethanol restricts blood vessels limiting levels of nutrients that can pass to the fetus for essential growth
- Less blood and nutrients to the fetus
Teratogens
Smoking
Increased risk of:
- Preterm birth
- Additional risk of poor physical and neurodevelopmental outcomes
- Low birth weight
- Birth defects to lips and mouth
- Sudden infant death syndrome
Teratogens
Smoking and Face Touching
Reissland et al. (2015)
Significantly more face touching in fetuses of smoking mothers
- Indicated atypical development of CNS
- Other nerves have not developed enough to get sensory feedback from
Teratogens
Maternal Mental Health
Stress
- Bell et al. (2012): Higher cortisol levels in newborns in mothers who scored higher on Perceived Stress Scale
- More alert but affects sleep, recovery, and rest important for brain structure and organisation
