Foetal Growth Flashcards
Phases of fetal growth
- Hyperplasia- 4-20 weeks = increase in foetal weight, protein content and DNA content
- Hyperplasia with concomitant hypertrophy- 20-28 weeks = increased protein and weight and lesser increases in foetal DNA content
- Hypertrophy- 28-term = continue to increase in foetal protein and weight but no increase in DNA
intrauterine growth restriction (IUGR)
Failure to reach growth potential.
85% of unexplained still births may be due to restricted growth
children will catch-up growth during childhood, but have increased chance of diabetes and obesity in adult life. This is due to growth, metabolism and vasculature as well as postnatal factors that are also important
SGA and LGA
Small for gestational age, less than 10th centile for population, age, maternal weight, etc. (may be normal) and large for gestational age, more than 90th centile.
LBW
Low birth weight, less than 2500g
Intergenerational effects of SGA
Mothers who suffer from SGA are more likely to have SGA children. Maternal undernutrion also increases adiposity, glucose intolerance and CV risk .
Mechansisms for transgenerational effects of SGA
Epigenetic - heritable changes in gene expression, e.g. DNA methylation, microRNA, histone modificaiton. - materal mitochondiral changes due to food restriction.
Causes of LGA
Gestation >40weeks, male, maternal obesity, multiparity, genetic. Too much insulin from mother = more insulin for fetus = increased stores = increased weight, esp around cheeks, shoulders, head.
Barker hypothesis
Problems in fetus does not follow linear pattern, but follows U shape. SGA and LGA babies are both at risk of neonatal and adult disease.
Causes of abnormal growth
Can be maternal, feotal or placental.
Maternal factors for abnormal growth
- Ethnicity, BMI
- Smoking, drugs and alcohol
- Nutrition of the mother does not have a large effect on the foetus as the placenta acts as a parasite – placenta takes what it needs from the mother at the expense of the mother
Only really effected with very bad eating disorders/starvation - hypoxia due to cyanotic heart disease, chronic respiratory disease or altitude can effect the working of the placenta
Foetal factors for abnormal growth
- Chromosome disorder – trisomy 18 (Edward’s syndrome)
- Inherited growth factor disorders like insulin like growth factor or thyroxine
- Congenital infections that cross the placenta and effect the baby such as rubella
Placental factors for abnormal growth
- Primary placental problems = abnormality of placenta structure and function, could have an extra lobe or be implanted in the wrong place on the uterus
- Secondary placental problems = due to conditions of the mother like hypertension, chronic renal disease
- Multiple gestation = babies that share the placenta unevenly so baby with smaller placental share will be growth impaired
Asymmetrical vs symmetrical patterns of IUGR
Asmy = preserved head/heart growth but reduced abdominal growth. More likely to be placental problem as blood diverted to essential organs. Sym= more likely to be maternal problem.
What is abnormal placentation
failure of trophoblast invasion causing high resistance system, clinically indicated by changes in uterine artery waveform
what is symphsio-fundal height
Measuring the size of the uterus by measuring the mother’s abdomen
- Not very accurate and is effected by maternal height, weight, fibroids, extra muscle growth in uterus and can only be done on mothers with one baby
- However, it is cheap and easy and can be done anywhere
Ultrasound gives more accurate measurements
- Can estimate the foetal weight using circumference of head, abdomen and femur
- This is done every 3 weeks from 24 weeks onwards to create a foetal growth assessment
- However, if far more expensive so shouldn’t be done on every patient only high risk ones
