Normal Fetal Growth Flashcards
When is fetal growth the fastest?
Before term
When does the baby gain the most weight?
Mid/late trimester
Define fetal growth
The increase in mass that occurs between the end of the embryonic period and birth
What are the two components which determine normal fetal growth?
Genetic potential
Substrate supply
What is substrate supply dependent upon?
Uterine and placental vascularity
What is genetic potential mediated via?
Growth factors e.g. IGF
What are the three phases of normal fetal growth and when do they take place?
- Cellular hyperplasia (4th-20th week)
- Hyperplasia and hypertrophy (20-28th week)
- Hypertrophy alone (28th-40th week)
In the alphabet: p>t
Distinguish between hypertrophy and hyperplasia
Hypertrophy - increase in cell SIZE
Hyperplasia - increase in NUMBER of cells
Besides increase in cell size, what happens during hypertrophy in the last phase of foetal growth?
Rapid accumulation of fat, muscle and connective tissue
Which four fetal organs grow rapidly in size during pregnancy?
LARGE:
Brain
Liver
SMALL:
Kidney
Heart
How do foetal organs compare to baby organs?
They contain 20% less cells, therefore must growth after birth
What is the average weight gain between 14 and 15 weeks?
5g/day
What is the average weight gain at 20 weeks?
10g/day
What is the average weight gain between 32 and 34 weeks?
30-35g/day (triples)
What happens to the weight gain after 34 weeks?
Growth rate decreases
Name and describe a bedside technique used to determine the health and growth of the baby
Symphysis fundal height (SFH)
Measure the distance from the pubic symphysis to the top of the uterus
At which week is the SFH at:
i) the pubic symphysis
ii) the umbilicus
PS - 12 weeks
U - 20 weeks
Between 20 and 34 weeks, what would the SFH be?
Gestational age plus or minus 2 cm
e.g. at 25w, it could be between 23 or 27cm
Between 36 and 38 weeks, what would the SFH be?
Gestational age plus or minus 3 cm
After 38 weeks, what would the SFH be?
Gestational age plus or minus 4 cm
State four reasons for why the SFH may be smaller than expected
Baby may be small for its gestational age
Oligohydramnios (reduced amniotic fluid)
Transverse lie (baby may be lying in different position)
We may have the wrong dates
State seven reasons for why the SFH may be larger than expected
We may have the wrong dates Multiple gestation Large for gestational age Polyhydramnios Maternal obesity Fibroids Molar pregnancy
What are the pros of SFH?
Simple
Inexpensive
What are the cons of SFH?
Low detection rate
Great inter-operator variability
Influenced by many factors (BMI, fetal lie, amniotic fluid, fibroids)
What is molar pregnancy?
When an unviable fertilised egg implants in the uterus and fails to come to term
Unviable because of abnormal number of chromosomes (e.g. fertilised by two sperm, or the egg doesn’t have any nuclei inside)
How else can the age of the fetus be estimated?
Dating by last menstrual cycle
Give four reasons why dating by LMP may be inaccuate
Irregular periods
Abnormal bleeding
Oral contraceptives
Breastfeeding ??
State three reasons why determining the baby’s date is important
To avoid small/large gestational age confusion
To ensure that inductions are given at the right time if the baby is due
To ensure that steroids can be given at the right time in preterm delivery, to promote lung surfactant in the fetus
In the modern day, how are babies dated?
Crown-rump length (length of baby sagitally)
Which group of babies are not dated by crown rump length?
IVF babies
What is used to date the pregnancy if the first scan is done after 14 weeks?
Head circumference
Give two situations when head circumference is used to date the baby
If first scan is done after 14w
If CRL is above 84mm
Which four parameters are used to estimate fetal weight (EFW)?
Biparietal diameter (BPD) Head circumference (HC) Abdominal circumference (AC) Femur length (FL)
What is done with these measurements?
Plotted on a centile graph to see growth curve to assess neonatal/obstetric complications
Give nine maternal factors influencing fetal growth
Age (e.g. older woman vs younger woman) Weight Diet Alcohol, drugs and smoking Disease Environmental toxins Poverty
Give four maternal diseases/conditions which could affect fetal growth
Hypertension
Diabetes
Coagulopathy
Prenatal depression
Give four feto-placental factors influencing fetal growth
Genotype (genetic potential)
Gender B>G
Fetal hormones
Previous pregnancy
Give five fetal hormones influcing fetal-placental growth
Somatotrophin (GH) FSH/LH Insulin Androgens Iodothyronines (by third trimester)
Which hormone is not produced by the fetus but is involved in pregnancy?
Prolactin
Which two organs produce androgens in the fetus?
Adrenals and gonads
How is a customised growth chart made to be as accurate as possible?
Based on fetal weight curves derived from normal pregnancies
Adjusted to reflect maternal factors e.g. height, weight, ethnicity, parity (previous successful pregnancies)
Optimised by excluding pathological factors ?
Give the advantages of obstetric ultrasound examination
Assesses fetal wellness + size Looks at trends in growth Predicts fetal metabolic compromise Anticipates need for premature delivery Gives a chance to liase with neonatal services for them to be present at birth
What is parity in a medical sense?
Number of previous successful pregnancies
Give an example of a condition causing a larger than average baby
Gestational diabetes - causes macrosomia (large baby)
Give two fetal abnormalities
Neonatal hydrocephalus
Achondroplasia
