10.3 - Postnatal and child development 1/2 Flashcards
1
Q
What factors can affect prenatal / postnatal growth? (4)
A
- genetics
- endocrine
- nutrition
- environment
2
Q
How do genetics affect prenatal growth?
A
- minor effect overall
- maternal size important in determining birth size
- paternal genetic factors have little effect on birth
- maternal factors tend to override foetal genetic factors in determining prenatal growth
3
Q
How do genetics affect postnatal growth?
A
- largely determines final adult height
- sex chromosomes have an affect:
- XY boys are taller than XX girls
4
Q
How do endocrine factors affect prenatal growth?
A
- insulin and insulin-like growth factors (IGFs) are major prenatal hormones influencing growth:
- IGF-2 most important for embryonic growth
- IGF-1 most important for later foetal and infant growth
- (growth hormone has no effect on early growth)
5
Q
How do endocrine factors affect postnatal growth?
A
Human growth hormone (hGH) is the major hormone controlling growth after birth
6
Q
How does nutrition affect prenatal growth?
A
- placenta provides all nutrients to growing foetus, therefore essential for growth
- placental insufficiency most common cause of intrauterine growth restriction
- placenta also controls hormones necessary for foetal growth
- maternal diet influences nutritional availability
7
Q
How does nutrition affect postnatal growth?
A
- adequate nutrition is essential for growth
- starvation due to lack of substrate availability can limit growth potential
- obesity mainly occurs as a result of excessive intake of food
- poor nutrition may delay the onset of puberty
- malabsorption of nutrients may cause reduced growth
8
Q
How does the environment affect prenatal growth?
A
- uterine capacity and placental sufficiency important in providing optimal environment for foetus
- placental function is more influential in foetal growth than uterine capacity
9
Q
How does the environment affect postnatal growth?
A
The following factors are known to influence growth:
- socioeconomic status
- chronic disease
- emotional status
- altitude (mediated by lower oxygen saturation levels)
10
Q
What is the size of the head like at birth, and how does this change?
A
Head disproportionately large for the body at birth (1/3rd vs 1/7th in adulthood)
11
Q
What is the overall growth (of the head?) like in the first two years of life vs after, and why?
A
- grows rapidly for the first 2 years, before slowing down
- cranial sutures open at birth and close by 18 months
12
Q
What are the four recognised phases of growth (and what % of adult height do they contribute to)?
A
- fetal (30%)
- infantile (15%)
- childhood (40%)
- pubertal (15%)
13
Q
What is important in the fetal phase of growth?
A
Uterine environment
14
Q
What is important in the infantile phase of growth? (3)
A
- nutrition
- good health and happiness
- thyroid hormones
15
Q
What is important in the childhood phase of growth? (4)
A
- growth hormone
- thyroid hormones
- genes
- good health and happiness
16
Q
What is important in the pubertal phase of growth? (2)
A
- testosterone and oestrogen
- growth hormone
17
Q
What is the fastest period of growth over the life-course?
A
Fetal growth phase
18
Q
Describe the fetal growth phase.
A
- fastest period of growth over life-course
- accounts for approximately 30% of eventual height
- foetus repeatedly doubles in size over gestation
- growth mainly driven by hyperplasia during fetal life:
- ~42 cycles of cell division before birth
- ~only further 5 cycles of cell division from birth to adulthood
19
Q
What is growth in the fetal growth phase mainly driven by?
A
Hyperplasia (cell division)
20
Q
Describe the infantile growth phase.
A
- covers 0-18 months after birth
- accounts for approximately 15% of eventual height
- rapid, but decelerating growth (compared to fetal phase)
- length increases by 50%, head circumference by 30% and weight triples (vs birth)
- growth largely nutrition dependent
21
Q
What is growth in the infantile growth phase largely dependent on?
A
Nutrition
22
Q
Describe the childhood growth phase.
A
- covers 18 months to 12 years of age
- accounts for approximately 40% of eventual height
- steady, slow, prolonged growth
- 5-6cm annual increase in height, 3-3.5kg annual increase in weight
- good nutrition and health important, but endocrine growth regulation increasing
23
Q
Describe the pubertal growth phase.
A
- AKA pubertal growth spurt
- accounts for 15% of eventual height
- rising levels of sex hormones boost human growth hormone (hGH) production
- ~25cm (XY boys), ~20cm (XX girls) increase in height over 3-4 years
- temporary growth spurt as sex hormones also cause fusion of growth plates
24
Q
Why is the pubertal growth phase only a temporary growth spurt?
A
Temporary growth spurt as sex hormones also cause fusion of growth plates
25
Describe the activity of the HPG axis over the life-course.
- fetal - development of sexual organs and GnRH network, foetal HPG axis activity peaks around 20 weeks
- neonatal - priming of HPG axis, 'mini-puberty'
- childhood - linear growth and developmental milestones, HPG shut down until puberty
- adolescence - sexual maturation, normal puberty, HPG activity rises
- adulthood - reproductive capacity, HPG activation stays high
26
Describe gonadotrophin secretion during pregnancy.
Gonadotrophin secretion commences towards the end of the first trimester, peaks mid-pregnancy, then declines
27
What is mini-puberty?
- HPG axis transiently activated after birth (mini-puberty), after release from restraint by placental hormones
- continues for around 6 months after birth before declining
## Footnote
Males: T elevated
Females: E2 fluctuates
28
What is the point of mini-puberty?
- elevated sex steroids in males during mini-puberty seems to be important for normal gonadal development (testicular tissue and penile development)
- role of mini-puberty less clear in female infants:
- oestradiol levels fluctuate through first few months after birth
- follicular development occurs in the ovary
- important for patterning and development of mammary tissue?
- elevated sex steroids in mini-puberty may also influence programming of body composition and linear growth
- high testosterone levels in boys during mini-puberty may partly explain the higher growth velocity observed in boys vs girls
29
What triggers puberty?
- control of puberty onset remains unclear, but influenced by metabolic status
- release of neurokinin KNDy neurons may regulate release of Kisspeptin peptides, which act on GnRH neurons to promote pulsatile GnRH release
- mutations in KISS1R affect puberty timing, implicating Kisspeptin-KISS1R signalling in regulation of this process
- adiposity also plays a role
30
What do the developmental events of puberty typically follow?
The developmental events of puberty typically follow a predictable pattern
31
What is compliance with the predictable pattern of developmental events of puberty known as?
Consonance
32
How has the age of menarche changed?
Decreased ~4y from 1850-1960, then by a further 3 months per decade from 1977-2013 (partly due to better nutrition and health status)
33
Describe the developmental milestones during puberty in a female.
- breast budding
- growth of pubic hair
- growth spurt (peak)
- first period (menarche)
- growth of underarm hair
- change in body shape
- adult breast size
34
Describe the developmental milestones during puberty in a male.
- growth of scrotum and testes
- change in voice
- lengthening of penis
- growth of pubic hair
- growth spurt (peak)
- change in body shape
- growth of facial and underarm hair
35
What are the four developmental domains?
- gross motor skills
- fine motor skills
- speech, language and hearing skills
- social behaviour and play skills
36
Describe the development of gross motor skills.
- newborn: flexed posture
- 7 months: sits without support
- 1 year: stands independently
- 15-18 months: walks independently
- 2.5 years: runs and jumps
37
Describe the development of fine motor skills and vision.
- newborn: fixes and follows face/object
- 7 months: palmar grasp (4-6 months), transfers objects from hand to hand
- 1 year: pincer grip (10 months), points
- 15-18 months: immature grip of pencil, random scribble
- 2.5 years: draws
38
Describe the development of speech, language and hearing skills.
- newborn: stills to noise, startles to loud noise
- 7 months: turns to voice, polysyllabic babble
- 1 year: 1-2 words, understands name
- 15-18 months: 6-10 words, points to four body parts
- 2.5 years: 3-4 word sentences, understands two joined commands
39
Describe the development of social behaviour and play, emotional and behavioural skills.
- newborn: smiles by 6 weeks
- 7 months: finger feeds, fears strangers
- 1 year: drinks from cup, waves
- 15-18 months: feeds self with spoon, beginning to help with dressing
- 2.5 years: parallel play, clean and dry
