Fetal Adaptations To Pregnancy

Question 0

Reasons for low birth weight

Answer 0

Preterm pregnancy
Multiple pregnancy
Genetics
IUGR

Question 1

Factors influencing fetal growth

Answer 1

Fetal genome
Maternal height in relation to uterine capacity
Maternal nutrition
Placenta malfunction 
Fetal sex

Question 2

Effects of insulin like growth factors

Answer 2

IGF1 and 2 produced by fetal cells including placenta
Synthesis increases through pregnancy
2-3x more IGF2
IGF1 produced in response to nutrient levels, decrease with nutrient levels
IFG1 productions also sensitive to insulin, thyroxine, glucorticoids-> match fetal growth to maternal nutrient supply
IGF2 stimulates placental growth and transport mechanisms
IGF2 paternally expressed
Increased recourse extraction from mother

Question 3

Gradients that drive diffusion exchange

Answer 3

pO2 in umbilical vein is low compared to maternal blood
pCO2 high in umbilical artery compared to maternal blood
O2 saturation is high in fetal blood-> much lower pO2 still leads to similar O2 content-> fetal blood has higher O2 trapping capacity
2 gamma instead of beta chains-> doesn’t bind 2DPG
double Bohr effect-> fall in pH of maternal due to uptake of fetal CO2-> release of maternal O2 and rise in fetal due to CO2 removal
Switch to adult Haemoglobin happens several months after birth

Question 4

Fetal CV system

Answer 4

Ductus venosus-> oxygenated blood in fetal vein-> two channels-> larger is ductus venosus-> bypasses hepatic circulation
Small amount of blood enters liver-> regulated by sphincter-> blood shunted here during uterine contraction
For amen ovale-> IVC carries blood to RA-> split into two streams by crista dividens-> larger through foremen ovale to LA
Ductus arteriosus-> smaller stream-> RA-> RV -> pulmonary artery-> ductus arteriosus-> aorta or small amount to lungs

Question 5

CV changes at birth

Answer 5

Initiated at first breath
Closure of umbilical arteries-> contraction caused by thermal, mechanical and pO2 change
Closure of umbilical veins and ductus veinosus-> placental blood no longer reaches heart-> minutes after birth
Closure of ductus arteriosus-> contraction of muscular walls-> blood must go to lungs-> bradykinin released by lungs after initial inflation, complete obliteration takes 1-3 months
Closure of foramen ovale-> increased pulmonary blood flow-> increased pressure in LA-> decreased pressure RA

Question 6

Respiratory system

Answer 6

Surfactant production starts 2 months before birth
No surfactant-> respiratory distress syndrome
Fetus makes rapid respiratory movements 1-4 per day
Moves amniotic fluid in and out of lungs-> lung development and resp muscle conditioning

Question 7

Renal system

Answer 7

Kidneys are functional during pregnancy 
Produce amniotic fluid
Produce lots of hepatouric urine
Inefficient Na reabsorption 
Fetal urine-> 0.5l/day to amniotic fluid

Question 8

Nervous system

Answer 8

Fetus can respond to extraneous stimuli form 2nd trimester
Loud noises, intense light, rapid temp decrease
Results in changed movement and increased heart rate
Pain detected at 29 weeks
Immature blood brain barrier-> opioids and nictine can produce dependence

Question 9

Sub optimal intrauterine conditions

Answer 9

Poor maternal diet 
Maternal stress
Hypoxia 
Drugs
Endocrine disrupting chemicals 
Alcohol

Question 10

Suboptimal intrauterine conditions lead to…

Answer 10

Placental insufficiency 
Poor placental growth 
Poor transport mechanisms
Impaired barrier
Vascular dysfunction 
Increased cortisol secretion 
Aberrant invasion of decidua and spiral artery re modelling

Question 11

Consequences of placental insufficiencies

Answer 11

Small baby 
Intrauterine growth restriction 
Metabolic changes in infants
Obesity 
Impaired glucose tollerance 
Insulin resistance
Dyslipdemia 
Obesity 
Type 2 
Metabolic syndromes in adults

Question 12

Barker hypothesis

Answer 12

The lower the weight of the baby at birth and infancy the higher the risk of CV disease

Question 13

Dutch famine disease

Answer 13

Low birth weight associated with risk of hypertension, stroke and diabetes
Maternal diabetes and macro soma-> CV and metabolic disease

Question 14

Evolutionary changes

Answer 14

Low birth weight babies-> survival value for selecting genes that reduce fetal growth in response to maternal nutritional stress as a way of preparing the offspring for optimised survival in resource poor world
However if recourses are fine-> catch up growth is bad of for health

Question 15

Thrifty gene hypothesis

Answer 15

Early in evolutionary history-> genes that promoted fat deposition would’ve been useful to survive famine
In modern society these genes aren’t useful
Disease and diabetes
Early life metabolic adaptions help survival of organism by selecting appropriate growth trajectory in response to environmental ques

Question 16

Epigenetics

Answer 16

The mechanism of regulating gene expression without altering the DNA sequence

Question 17

Epigenome

Answer 17

The machinery that regulates gene expression-> alters phenotype
Histones-> wrapped around DNA-> controll when the complex opens so code can be read

Question 18

Epigenetic modification

Answer 18

DNA methylation-> addition of methyl groups to cytosine-> activate or repress genes
Histone modification-> methylation affects hi stones-> alters DNA wrapping and availability of genes to be activated

Question 19

Examples of epigenetic modification

Answer 19

Reprogramming during gametogenesis-> differ in spermatogenic and oogenic lineage-> uni parental imprinting
After fertilisation-> rapid demethylation of entire maternal nome and slower of paternal. Not on imprinted genes
Can be modulated throughout life

Question 20

Parental imprinting

Answer 20

For majority of genes expression is bilallelic
80-100 one parent silences their own gene-> parent specific monoallelic expression
IGF is paternal
Gnasxl paternally expressed-> suckling