Fetal growth Flashcards
What is normal fetal growth
Three phases
First
-4-20 weeks
-increases in fetal weight,
-due to increase in protein content and DNA content (cellular hyperplasia)
-development of tissues, organs, structures
-simialr weight at 20 week mark across most babies
Second
-20-28 week
- increased in protein and
weight
-gorwth of liver and brain
-lesser increases in fetal DNA content
-hyperplasia and concomitant hypertrophy
Third
-28 weeks
increased fetal protein and weight
-no increase in DNA
-hypertophy
How can we measure fetal growth
-use a growth chart
-tape measure from symphsis pubis to top of fundus (y axis)
-x axis is gestational age
-mark up with cross to work out age
Defintitions
Fetal growth restriction (FGR)
Failure of a fetus to achieve his or her
growth potential
-genetically meant to be bigger, but smth patholgical occured
Small for gestational age (SGA)
Birth weight <10th centile for gestational age
– Centiles are based on local populations
– Can be adjusted for sex, parity, race,
maternal weight and heigh
Large for gestational age (LGA)
Birth weight >90th centile
Low birth weight (LBW)
-birth weight less than a certain threshold
e.g. 2500g
What are the consequences of fetal growth restrictions
pathological process
-may cause perinatal and neonatal death
-LBW babies more likley to die in first year, can suffer with asphyxia, hypoglycermia, hypothermia
-growth origin of adult disease
What is the barker hypothesis
what happens in utero affects you for the rest of your life
-if you suffer from metabolic syndrome, and something alters growth, more likley to have metabolic programming that puts you at risk of metabolic diseases in adult hood
If your mother has impaired nutrition what can that alter
-can alter appetitie centres develop
-can alter kidney response to conditions -> can get hypertension
-more likely defective beta cell function -> can cause insulin defiency
-more likley to have altered adipose tissue, which can lead to obesity
-blood vessles can be altered -> hypertensuin
Get a thrifity phenotyoe
-you try to make the most of every nutrition
-Evolved like this to offer advantage in a “famine environment”
- but moretime when the chld is born they may be in industrialised society
What intergenerational effects are there
Mothers who had a small gestetional age
-more likley to have SGA babies
-increase perinatal mortaloty
Based on rodent models when can we break the intergenerational effects
After undernutrition for 12 generations,
-takes around 3 gen to restore normal fetal growth and development
What can maternal undernutrition have on subsequent generations
ncrease adiposity,
glucose intolerance and cardiovascular risk in F1 and F2 generations
What are the mechanims for transgenerational effects
how does it happen
-may be due to epigenetics via DNA methylation, histone modifcation, micro RNA
In maternal mitochondria
-food restriction can alter
number and function
Directly passed onto to offspring through ova.
epigenetics: heritable changes in gene expression
by mechanisms other than underlying DNA
sequences
What are the causes of LGA
large for gestatioanal age
- Gestational age; pregnancies that go beyond 40 weeks increase incidence
- Fetal sex; male infants tend to weigh more than female infants
- Excessive maternal weight gain and obesity
- Multiparity (more children yoy have the bigger your babies are have 2
- Erythroblastosis fetalis - Hydrops Fetalis
- Genetic disorders of overgrowth (babies express genes like e.g. Beckwith-Wiedemann syndrome, Sotos syndrome)
- Maternal diabetes (the most common cause of pathological overgrowth -> pre-existing or gestational)
maternal diabetes
yiu get increase maternal glucose conc -> glucose corsses placenta -> baby makes for insulin -> they start making more fat
=have bigger abdomen circumferances
What is the pathophysiology behind LGA
matenral diabtes
- Increased maternal glucose concentrations
glucose corsses placenta - Increased fetal insulin concentrations
- Increased fetal growth factors
- babies have bigger abdomens but notmal head circumferance
What causes abnormal growth
can be genetic
enviorment causes
-maternal
-fetal
-placental
What maternal factors can affect growth
Mothers Ethnicity
* Maternal stature/BMI
– Maternal v paternal influence
* Drugs
– Cigarettes (toxic to placenta, cause growth restriction)
-alcohol, drugs
* Nutrition
-> lacking micronutrient affects growth
* Maternal hypoxia (cyanotic heart disease, chronic respiratory disease,
being born at altitude)
What did we learn about the dutch famine
-if famine had hit the third trimerster -> reduces birth-weight of baby (started
-if famine had happened throughout pregancy (they adapted -> babies where in the thrifty enviorment)
-so babies wont always become fmall
-babies had late gestataion
-decreased birthweight
What are fetal factors that can affect griowth
- Genome
– Chromosomal disorders - Growth factors
– Insulin like growth factors,
thyroxine - Congenital infection
– Cytomegalovirus (CMV),
Toxoplasmosis, rubella
What placental factors affect growth
- Primary placental problems
– abnormality of placenta
structure/function)
Secondary placental
problems
-Mums has problems
– Hypertension (uterine arteies dont model themselves well)
– Chronic renal disease
– Vasculitis
– Pro-thrombotic disorders
-this then affects placenta
Multiple gestation
– decreased surface area
Malplacentation in IUGR
-uterus blood flow supplued by uterine arteries (supplied by arcuate and spiral arteries)
-shape of uterine artery waveform is unique
-in early pregenacy there is high vascular impedance and low flow
-what happens is body releasies its preganant
mid preganancy theres high flow and low resustance (cardiac output to placenta is a lot in pregnant mother)
-can get poor trophonblast invasion into maternal spiral aterties
-if trophoblast invasion does not occuur _> you get increased impedance to flow and decreased placental perfusion -> which causes growth probelms
How can we see if placental blood flow is going through problems
use a uterine artery doppler waveform
-its seeing if uterine artery is handling blood flow well
-if theres raised resistance there is less blood flow to placenta -> risk of growth problem
If there is a growth problem due to IUGR what happens
-you start growing normally
-but then things change
-the fetus goes all out to protect brain, and the fetus stops growing their abdomen
-this is called asymmetric growth
we do additional tests like measuring uterine arteyr, baby blood flow
What happens in an antenatal appointments
for fetal growth
low risk women: measure abdomen (fundus to symphysis)
high risk women
-measure femur length, head circumferance, abdomen cirucmfernace)
-use measurments an estimated fetal weight
If we think there is a problem with fetal growth
what can we do
- we can do cardiotocograph to see short term wellbeing
-if we want to know long term wellbeing we can measure blood flow in umbilical artery, middle cereberal artery and ductus stenosis
-if blood flow is being divereted elsewhere (to brain) then we will see more middle cerebral artery acvity than normal
What are the risk factors for small growth baby
Maternal risks factors
-age over 25
BMI increased
-hypertension
-diabetes
-previous pregnancy history
-weight gain
-exposure (cigaraaettes drugs)
theres more …
coccaine: 3x more likely to have growth restriction, due to vasoconstriction -> causes vasoconstriction to placenta
What risks can happen in pregnancy that can make the child at risk of growth restrictions
-heavy bleeding
pre-eclampsia
-hypertension (pregnancy)
-placental abruption
-
When do we measure SFH
each appointment from 24 weeks
Uterine artery Dopplers in second trimester
if a fetus is small
should do extra monitoring
CTG
* Dopplers and liquor volume
-if doppler suggets risk of stillbirth is high, then baby should be delievered
What is gestational diabetes
-Gestational diabetes mellitus (GDM) is defined as any degree of glucose intolerance with its onset (or first recognition) during pregnancy
* occurs in 5% pregnancies
What is a pre-existing risk of GD
-deficent insulin production
-theres chronic insulin resistance
-this was present before pregancyc
-prgancy is a state of insulin resistant
-resistant increases with gestation
-so can flip from a pre-diabetic state to diabetic state
When do we screen for GD
** Screen from early pregnancy 16-18 weeks if:
**–Past history of GDM or glucose intolerance
**Screen from 24-26 weeks if:
**–Family history of diabetes (first degree relative)
–PCOS
–BMI > 30
–Ethnicity: Asian, Black, Middle Eastern
–Previous macrosomia >4500g (previous big baby)
–Previous unexplained stillbirth
–On steroids (e.g. prednisolone) -> say your on it for asthma
**Screen urgently if arises in current pregnancy:
**
–Significant glycosuria (3+ glucose at any time or 2+ on two or more occasions)
–Polyhydramnios and macrosomia
* Screen via:
–Oral Glucose Tolerance Test (overnight fast then 75g glucose load, test at 2 hrs)
–Random blood glucose profile >36 weeks
in some centres theres lots of women with risk factors
so they just screen
What are the GDM for the mother
- Pre-eclampsia
- Pre term labour
- Instrumental delivery / Caesarean section
- Diabetes in later life
What are complications of GD for a child
- Macrosomia
- Shoulder dystocia
- Polyhydramnios
- Perinatal mortality and morbidity
Neonatal hypoglycemia, jaundice, polycythemia,
and hypocalcemia - Fetal programming and increased risks of adult diseases
shoulder dystocia
extra growth around shoulder, when baby is coming out, shoulder gets stuck under symphysis, when baby is half in and out, pressure on chest, means heart stops beating because chest can’t expand
may break clavicle, deliver baby posterioly,
Who is involved in diabetes managments
Multi-disciplinary:
– Obstetrician
– Diabetologist
– Diabetic nurse
– Dietician
How often does blood pressure get monitored
around 7 days
How do we measure GDM
-Diet
– Oral agents e.g. metformin
– Insulin
Tight glucose control reduces risk
How do we measure child growth
- Regular growth scans
- Regular BM monitoring
- Deliver around 38 weeks depending on diabetes
-most times they try to deliver aorund - Offer GTT 6 weeks postnatal
-assess to see if woman has ongoing diabetic risk, offer GTT at 6 weeks to see if diabetes has gone away since placenta has, if it hasnt it mean she has type 2 diabetes
