Prenatal Development Flashcards
Prenatal – what does this mean?
Prenatal = before (pre) birth (natal)
9-month period from conception to birth constitutes the first stage in human development and is divided into 3 substages
1st stage of Prenatal period
Germinal stage
0-2 weeks
Sperm penetrates egg to form a zygote
This contains 23 pairs of chromosomes – inherited aspects from mother & father (50/50). These make up the individual’s genotype and phenotype
Zygote following cell differentiation becomes a blastocyst and begins to implant into the wall of the uterus – at which point the germinal stage ends.
2nd stage of Prenatal period
Embryonic stage
week 3 to around week 7/8
Cell differentiation continues until 350 different cell types are formed
Ectoderm, endoderm & mesoderm cells form different bodily aspects
By week 8, embryo is 2cm in length
All changes reflect choreographed changing patterns of cells to achieve the species-typical shape of the organism
3rd stage of Prenatal period
Foetal stage
Week 8/9 to week 38-40
Coincides with major developments of the nervous system
Rapidly takes on distinctively human characteristics & by week 12 is easily recognisable
By week 16, embryo is 15-17cm but cannot survive outside of the mother
Foetus continues to develop for the normal 40 week gestation period
The prenatal environment key points
Critical for normal development
(see Knopik et al., 2016)
Changes to environment can be catastrophic for foetus and neonate
But, foetal behaviour also contributes to normal development – not simply a matter of automatic maturation, more than just a reflexive responder
Prenatal risk factors – Teratogens
Exposure to teratogens during prenatal stage can significantly raise the risk of birth defects
Teratogens:
“Environmental agents that have the potential to
cause harm during prenatal development”
(Siegler et al., 2003)
Teratogens factors
Each of these aspects pose as potential risk factors for a developing child:
Legal drugs Nutrition Illegal drugs Disease Disease Pollutants Maternal Stress Maternal age
Teratogens are influences by???…
Timing of exposure Amount and duration of exposure Age Exposure to other teratogens Individual differences in susceptibility in the mother and the foetus
Rubella
AKA German measles
Rubella is caused by a type of virus known as a togavirus
Spread in a similar way to a cold/flu, droplets of moisture from the nose or throat of infected individual
Generally mild unless contracted during pregnancy, when there is a 90% chance of the foetus getting congenital rubella syndrome (CRS)
Rubella defects can cause
The baby can be born with multiple defects if it lives (miscarriage common)
Eye problems – such as cataracts(cloudy patches on the lens of the eye)
Deafness
Heart Abnormalities
Brain Damage
Zika Virus
Mosquito-borne virus
Infection, especially in the 1st trimester can cause microcephaly and other foetal brain defects
Between Oct 2015 – Jan 2016 almost 4000 cases of babies born with microcephaly in Brazil
Teratogens - Legal drugs: Thalidomide
considered a ‘wonder drug’ for morning sickness and was being prescribed worldwide
Late 1950s, children began to be born with shocking disabilities
The most renowned disability wasPharcomelia the name given to the flipper-like limbs which appeared in children
‘Thalidomide Babies’
Teratogens – Legal drugs: Primodos
pregnancy testing drug given to women in 1960s/70s.Consisted of two pills, inducing a period in women who were not pregnant
Teratogens – Legal drugs: Alcohol
Foetal Alcohol Syndrome (FAS)
mostharmful for the baby in the first 3 months of pregnancy
affect baby’s development, particularly the brain and spinal cord
Foetal Alcohol Syndrome (FAS) – symptoms:
Smaller than average head Poor growth – weight and height Changes facial features (all smaller than usual) Movement/Co-ordination issues (Cerebral Palsy) Learning difficulties Mood/attention/behavioural issues (ADHD) Weaker organs and immune system Hearing and vision