Foetal Growth Flashcards
how can foetal size be determined externally?
Symphysis Fundal Height (SFH):
Distance between pubic symphysis and fundus of uterus.
why may the SFH be lower than it should be?
- wrong LMP date
- baby lies in a transverse line
- oligohydramnios (low amniotic fluid levels)
- baby is small for GA.
why may the SFH be higher than it should be?
- wrong LMP date
- multiple pregnancy
- molar pregnancy
- maternal obesity
- polyhydramnios (excess amniotic fluid)
- large for gestational age
what complications affect the SFH reading (larger than usual)?
- molar pregnancies
- fibroids
- polyhydramnios
- llarge baby for GA
what are the main factors important for foetal growth?
- genetic potential (from the parents)
- substrate supply (derived from placenta vasculature)
when does foetal growth occur?
end of embryonic period to birth
what can be identified using ultrasound scanning?
o Crown- Rump length o Biparietal diameter (BD). o Head circumference (HC). o Abdominal circumference (AC). o Femur length (FL).
Combines into Estimated Foetal Weight (EFW).
what is ultrasound mainly used for?
- overall foetal wellbeing (i.e. chromosomal abnormalities)
- management of abnormal growth
- prediction of metabolic compromise
- anticipate premature delivery
what are customised foetal growth charts based on?
o Based on foetal weight curves for normal pregnancies.
o Adjusted to reflect maternal constitutional variation – i.e. mother weight.
o Optimised – with curves free from data influenced by pathological factors.
how does the growth velocity change with GA?
o 14-15 weeks -->5g/day. o 20 weeks --> 10g/day. o 32-34 weeks -->30-35g/day. o >34 weeks -->velocity decreases.
Fastest velocity is mid-third trimester.
what are the phases of normal foetal growth?
o Hyperplasia (rapid cell division) – 4-20 weeks.
o Hyperplasia and hypertrophy
– 20-28 weeks.
o Hypertrophy (most foetal weight gain) – 28-40 weeks
why is it hard to date a pregnancy? why is it important however?
there are issues knowing the LMP date i.e. planned vs. unplanned pregnancies, oral contraceptive use
important to classify GA and get it right
how can pregnancy be dated best?
ultrasound
– determining crown-rump length of foetus at the end of 1st trimester
variations in foetal size are more limited at this stage so more accurate date
what are some specific maternal factors affecting foetal growth?
Poverty
– more likely to be young (low birth weight) and be less educated on risks.
Mother’s age
– too young or too old can impact baby health.
Drug use and alcohol.
Smoking and nicotine.
Diseases.
Mother’s diet and physical health
– MALNUTRITION is the most important factor in baby growth.
Mother’s prenatal depression.
Environmental toxins.
what are the foeto-placental factors influencing foetal growth?
Different genotypes. Gender – males tend to be bigger than females. Previous pregnancy – infants are heavier in the 2nd and subsequent pregnancies. Hormones – one important hormone is IGF-1
what are the effects of IGF-1 in foetal growth?
- Increase mitotic drive.
- Increase nutrient availability for tissue accretion.
Little effect on tissue differentiation (this is mediated by cortisol).
what mediates tissue differentiation?
cortisol
SGA
Small for Gestational Age
– infant has a birth weight <10th centile
(AKA “Small for Dates”).
what is the definition of IUGR/FGR?
failure of the infant to achieve its predetermined (genetic) potential for a variety of reasons
Intrauterine growth restriction - the term is only used for those with definite with IUGR
LBW
Low Birth-Weight
– <2,500g
most LBW are not FGR
does not consider GA
VLBW
Very Low Birth-Weight
- <1,500g
does not consider GA
ELBW
<1,000g
does not consider GA
relationship between foetal growth and GA
A baby at term at 2,500g would be SGA but a baby of 2,500g ay 33 weeks’ delivery is normal (i.e. preterm)
- important to determine between pre-term babies that are of a LBW and those that are IUGR (at a greater risk).
what is the most sensitive centile in the IUGR age/weight graph?
10th
10th centile will capture all babies with IUGR but also those that are SGA.
i.e. captures false +ve.
what is the most specific centile in the IUGR age/weight graph?
3rd
3rd centile captures IUGR but also misses some.
no genetics considered
what is IUGR a common factor in?
stillborns
has serious consequences on post birth survival
subsequent pregnancies may be affected by IUGR
when does IUGR often occur?
develops in the 2nd and 3rd trimesters as the 1st stage focuses on embryology
what are the causes of IUGR?
Maternal medical factors
– infection, pre-eclampsia, uterine abnormalities, etc.
Maternal behavioural factors – i.e. alcohol.
Foetal factors
– i.e. multiple pregnancy.
Placental factors
– i.e. placental cysts, impaired trophoblast invasion.
what are the short term problems with LBW/prematurity/FGR?
Respiratory distress Intraventricular Sepsis Hypoglycaemia Necrotising Jaundice Electrolyte imbalance haemorrhage enterocolitis
what are the medium term problems with LBW/prematurity/FGR?
Developmental delay
Respiratory
Special needs schooling
what are the long term problems with LBW/prematurity/FGR?
foetal programming
what is the link between IUGR and pre-eclampsia?
main cause of pre-eclampsia is diminished remodelling of spiral arteries by cytotrophoblasts.
This causes decreased blood flow and hence decreased nutrient supply to the placenta and foetus.
what are the pros and cons of SFH use?
pros: • Simple • Inexpensive cons: • Low detection rate: 50-86% • Great inter-operator variability • Influenced by a number of factors (BMI, foetal lie, amniotic fluid, fibroids)
what are some consequences of abnormal foetal growth?
- neonatal hydrocephalus
- achrondoplasia
- macrosomia
what are the consequences of pre-eclampsia?
hypertension and proteinuria.
what would a blood pressure in pre-eclampsia (PET)?
what is the other sign for pre-eclampsia?
> 140/90
significant proteinuria (>300mg/day)
what are some maternal factors affecting foetal growth?
medical:
- diabetes mellitus
- chronic hypertension
- chronic infections
behavioural:
- smoking
- poor nutrition
- drugs
- living in altitude
what are some foetal factors affecting foetal growth?
- chromosomal abnormalities
- multiple pregnancies
- structural abnormalities
what are some placental factors affecting foetal growth?
impaired trophoblast invasion
what facilitates spiral artery remodelling?
cytotrophoblasts
how is a mother screened for pre-eclampsia risk?
- look for systemic diseases
- pHx of pre-eclampsia in previous pregnancies
- uterine artery Doppler scan (identify high resistance blood flow)
what must be given to a prematurely delivered baby (<30 weeks)?
glucocorticoids
what is the difference in handling a late and early IUGR?
late IUGR is easier to deal with than an early IUGR as this is most likely linked with pre-eclampsia
