1b Postnatal and Child Development Flashcards
(91 cards)
What are the genetic impacts on a fetus prenatally?
- Minor effect overall
- Maternal size important in determining birth size
- Paternal genetic factors have little effect on birth
- Maternal factors tend to override fetal genetic factors in determining prenatal growth
What are the genetic impacts on a fetus postnatally?
- Largely determines final adult height
- Sex chromosomes have an effect: XY boys are taller than XX girls
What are the endocrine impacts on a fetus prenatally?
- 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 fetal and infant growth
- (Growth hormone has no effect on early growth)
What are the endocrine impacts on a fetus postnatally?
- Human growth hormone (hGH) is the major hormone controlling growth after birth
What are the nutrition impacts on a fetus prenatally?
- Placenta provides all nutrients to growing fetus, therefore essential for growth
- Placental insufficiency most common cause of intrauterine growth restriction
- Placenta also controls hormones necessary for fetal growth
- Maternal diet influences nutritional availability
What are the nutrition impacts on a fetus postnatally?
- Adequate nutrition is essential for growth (Starvation due to lack of substrate availability can limit growth potential)
- Obesity occurs mostly as a result of excessive intake of food
- Poor nutrition may delay the onset of puberty; Malabsorption of nutrients may cause reduced growth
What are the environmental impacts on a fetus prenatally?
- Uterine capacity and placental sufficiency important in providing optimal environment for fetus
- placental function is more influential in fetal growth than uterine capacity
What are the environmental impacts on a fetus postnatally?
The following factors are known to influence growth:
* Socioeconomic status
* Chronic disease
* Emotional status
* Altitude (mediated by lower oxygen saturation levels)
What is the head size compared to the body at birth?
Head disproportionately large for the body (1/3rd vs 1/7th in adulthood) at birth
What is the pattern of growth after birth?
Grows rapidly for the first 2 years, before slowing
When do cranial sutures open and close?
open at birth, close by 18months
What are the four recognised phases of growth?
- Fetal
- Infantile
- Childhood
- Pubertal
What is the fastest period of growth over life-course?
fetal phase
What percentage of eventual height does the fetal phase account for?
30% of eventual height
How does growth occur in the fetal phase?
- Fetus repeatedly doubles in size over gestation
- Growth mainly driven by hyperplasia during fetal life:~42 cycles of cell division before birth,
~only further five cycles of cell division occur from birth to adulthood.
What period of time does the infantile phase cover?
Covers 0-18 months after birth
What percentage of eventual height does the infantile phase account for?
15% of eventual height
How does growth occur in the infantile phase?
- Rapid, but decelerating growth (vs fetal phase)
- Length increases by 50%, head circumference by 30% and weight triples vs birth
- Growth largely nutrition dependent
What period of time does the childhood phase cover?
18 months to 12 years of age
What percentage of eventual height does the childhood phase account for?
approximately 40% of eventual height
How does growth occur in the childhood phase?
- Steady, slow prolongued growth
- 5-6 cm annual increase in height, and 3-3.5kg annual increase in weight
- Good nutrition and health important, but endocrine growth regulation increasing
What is the pubertal phase also known as
The pubertal growth spurt
What percentage of eventual height does the pubertal phase account for?
15% of eventual height
How does growth occur in the pubertal phase?
- Rising levels of sex hormones boost 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