foetal growth Flashcards
foetal growth ie length vs and weight during pregnancy
most rapid at start, then length slowly plateaus, whereas fetal weight rises slowly at start, and becomes more rapid
3 phases of foetal growth
hyperplasia, then hyperplasia+ hypertrophy in 2nd trimester, then only hypertrophy in 3rd, thus hypertrophy key for fetal weight
SPH (symphysis fundal height) technique- purpose+ pros and cons
measure distance in abdominal wall between pubic symphysis and top of uterus to determine age of baby- it’s simple, but low detection rate+ affected by other factors eg mother BMI
what measure used to date pregnancies d, and what when after 14 weeks
by crown rump length ie top to bottom, or head circumferance if first scan AFTER 14 weeks
how ultrasound assesses foetal growth
measure biparietal diameter, head circumference, abdominal circumferance and femur length, and combine to form foetal weight, and then do this multiple times and plot on a foetal growth chart
maternal and fetoplacental factors affecting foetal growth
diet, alcohol, smoking, disease eg diabets, mothers age- fetoplacental factors include gender (males bigger), and hormons
customised growth chart
adjusted for maternal height/weight+ ethnicity
why ultrasound used
doesn’t just assess size, but also it’s wellness ie whether moving, whether it’s metabolically compromised- can also look at trends in growth, and whether baby needs to be delivered prematurely
define small for gestational age
birth weight below 10%
foetal growth restriction- define and danger
fetus doesn’t achieve its predetermined growth potential- most common cause for stillborn babies
determiants of early growth restriction
measure size, and umbilical doppler (blood flow)
effects of low birth weight/FGR
respiratory issues, sepsis, hypoglycaemia, developmental delay
causes of small for gestational age
may be foetal issue (eg abnormality/infection) or problem with placenta (eg pre-eclampsia- spiral arteries stay narrow), or could simply be dating issue
pre-eclampsia and cause
maternal hypertension (above 140) with proteinuria (above 0.3g) due to less remodelling of spiral arteries
when foetuses need monitoring
mum had previous maternal hypertension/FGR/stilll birth, and if there is abnormal PAPP-A in blood (above 0.3)
uteroplacental doppler screening
assesses uterine arteries ie whether there is high resistance- positive increases risk of pre-eclampsia ie FGR
sequence of events in blood vessels- uterine, umbilical, middle cerebral, ductus venosus
uterine arteries affected first, then umbilical arteries- babies then have increased flow to brain due to hypoxia (via middle cerebral artery), but less to lungs and kidneys (less to kidneys= less amniotic fluid): then less blood in ductus venosus, suggesting baby needs to be delivered soon
importance of CTG and foetal movement
if they are moving, indicating there is no hypoxia, so they will move, and heart rate (CTG) is normal
when FGR pregnancies delivered
above 28 weeks/above 500 g
early vs late growth restriction
early is rarer and more correlated to pre-eclampsia ie maternal disease: difficult to manage, whereas late is more common, less correlated to pre-eclampsia, and easy to manage (simply deliver)
what is low birth weight and significance
less than 2.5kg-
difference between low birthweight because born preterm and low birth weight because growth restricted
if you are growth restricted ie 2.5kg at term, means you are more vulnerable to abnormalities: if you are 2.5kg simply because you are born preterm, thats fine
sensitivity vs specificity when choosing centile
when choosing what centile to use for determining growth restriction, 10% most sensitive, but 3% most specific ie get false negatives ie some restricted babies might be misssed
when does growth restriction occur
mainly in 2nd/3rd, weight gain occurs mainly then
treating IUGR+ pre-eclampsia
corticosteroids eg for lungs
