Forming a New Life / The Prenatal Period
“Fertilisation or conception, is the process by which sperm and ovum - the male and
female gametes, or sex cells -combine to make a single cell called a zygote, which
then duplicates itself again and again by cell division to produce all the cells to make
up a baby” (Papalia, Olds & Feldman. 2009, p54)
Mechanisms of Heredity
The science of genetics is the study of heredity. (inborn factors inherited from the biological parents that affect development).
The Genetic Code the basic unit of heredity is DNA
deoxyribonucleic acid (Bases ATGC form the genetic code)
-genes: small segments of DNA, functional units,
found on the chromosomes
carry the genes
each cell has 23 pairs (46) except gametes which have 23 chromosomes
-3 billion base pairs constitute the genetic code which determines all inherited
Human genome: the complete sequence of genes in the human body
Specialised cells …gametes (sex cells)
ovum (stored in the ovary)
6 - 24 hours xx
spermatozoa (produced in the testes)
24-72 hours xy
-sex cell division to form gametes
-ova spermatozoa -22 + 1 chromosome
22 + 1
-xx - xy
• -mitosis cell division …two cells the same
- monomorphic genes....human state
- polymorphic genes…individual
Determination of sex of the individual
x y (male) (female) x xx xy
x xx xy
-occur in 2 ways
-monozygotic -one fertilised ovum splits very early
- identical twins (maternal)
-dizygotic (most common) -two ova are released
-non-identical twins (fraternal)
Patterns of genetic Transmission
The study of genetics is the study of heredity
….the inborn factors, inherited from the biological parents that affect our development
Gregor Mendal (Austrian Monk)
alleles Bb = alleles for blue eyes dominant genes B
recessive genes b
homozygous BB or bb
dominant inheritance BB or Bb
recessive inheritance bb
-phenotype: observable characteristics of a
-genotype: genetic makeup of a person,
containing both expressed and
Genetic and Chromosomal Abnormalities
Abnormalities may occur through mutation, inherited disposition, environmental
influences or multi-factorial.
dominant inheritance. eg. achondroplasia
recessive inheritance. eg. Cystic fibrosis
sex linked inheritance eg. Red / green
colour blindness -Genetic Counselling
–can help assess parents risk of bearing children with a genetic birth defect
Issues to discuss
• “Genetic testing and genetic engineering “
reference (Papilia, Olds and Feldman, 2009 p67)
Human Cloning: -issues:
Human Genome: -issues:
Statistical estimate of the contribution heredity makes towards individual differences in a
specific trait….within a certain population.
-Family / kinship studies
-twin studies Questions / Comments
The Prenatal Period and Environment
germinal stage ( fertilisation - 2 weeks)
organism divides….rapid cell division, increasing complexity , implants in the
uterus…forms the placenta and the amniotic fluid.
embryonic stage ( 2 to 12 weeks)
major body systems and organs develop.
-Critical period / stage
fetal stage (12 weeks - birth)
increasing development ……...growth
• What do you think it would be like in the intra uterine environment?
The intrauterine environment
placenta: delivers oxygen, nourishment, deals with elimination, helps maintain the pregnancy through hormone production
umbilical cord: connected to the placenta
amniotic sac and fluid: encases the fetus allowing room for movement, protection from outside and changes in temperature
membranes: surrounds the fetus inside the uterus
• Stimuli include:
capable of causing birth defects.
depends on the timing of exposure
intensity and co-interaction
Father / Mother
lead , marijuana , tobacco, alcohol, radiation, pesticides , chemicals , drugs of abuse,
diet low in vitamin C.
mother: medical drugs, nicotine, caffeine,
infections :TORCH, HIV, Aids
Ways for a pregnant woman to create a healthy prenatal environment for her child to be
Prenatal Assessment (not tested in this course but interesting to think about it in this context)
-chorionic villus sampling
-fetal movement, -fetal heart rate, -increase in abdominal size
-gestation 266 days (9 months)
-preterm (less than 37 weeks gestation) -term (37-42 weeks gestation)
-post term (over 42 weeks gestation)
The Newborn / neonate
average weight: 3000gm / 7.1/2 lbs length : 45-50 cms / 18-20 inches long size at birth is related to: race, sex , parents’ size, mother’s nutritional status and health. -features:
flexed body……..pink …….large head, small chin….nose breathers
-heart rate 100-120 beats per minute -temperature control….immature….needs warmth from the environment
-nose breathers until approx 3-4 months
-brain at birth 25% of adult weight…by age 12 years brain is full adult size.
-Brain growth is moulded by experience especially during early life……
Fetal / newborn environments
intrauterine / after birth
nutrition: mother’s food and
respiration: placenta respirations
stimulation: minimal much
elimination: placenta G.I tract
-reflexes: involuntary, automatic responses to external stimulation
-intact primitive pathways…neurological system
-reflexes include :
sucking, rooting , grasp, stepping, moro, babinski….
-disappearance indicates the cortex is maturing
-growth: rapid …double weight by 4-5th month
gross motor development:
-sequence the same in all infants
-wide variation to normal fine motor development -primitive.
Newborn / senses
least dev. at birth
focus approx. one foot away
responds….bright lights, faces , reds
and greens, curve lines to straight
by 4 -5 months binocular vision.
Touch: very sensitive to touch…feels pain
acute …responds mother’s voice, rhythmic noises
Smell: responds to unpleasant odours, can identify mother’s smell.
Taste: prefers sweeter to sour
? Implications for parents, nurses, to enhance optimal development
Theory to Practice
• What would Jean Piaget tell you about the best environment for a baby? Why?
• What would B.F. Skinner tell you about how a baby learns and therefore how you should behave?
• What would Ivan Pavlov tell you how babies learn?
• Albert Bandura would say……..
-the Infant mortality rate (IMR) is the number of deaths occurring in babies in the first
year of life.
New Zealand ranks 22nd out of 25 industrialised countries
(Papalia, Olds & Feldman 2009 p 111)
causes for infant mortality include: SUDIS, sudden unexplained death of an infant,
congenital anomalies and peri-natal conditions
Sudden Unexplained Death of an infant (SUDIS) or “Cot (crib) death”
“- the sudden death of an infant under 1 year of age which the cause of death remains
unexplained after a thorough investigation that includes and autopsy”.
(Papalia, Olds & Feldman 2009 p 112)
-? Combination of factors appear to explain why it happens
-following on from international research the Ministry of Health in New Zealand promotes
-“Back to sleep,” for sleep position
-no smoking around the baby
-baby sleeping in own cot or bassinette.