7.1 Foetal growth and development Flashcards
How long does an unborn baby spend in the uterus?
What is the average length of pregnancy?
38weeks
40weeks
When do we count the first day of pregnancy?
Pregnancy is counted from the first day of the woman’s last period (NOT the date of conception which generally occurs two weeks later)
What are the 3 stages that occur from fertilisation to birth?
What weeks do these occur between?
A: pre-embryonic/ germinal (0-2w)
B: embryonic (3-8w)
C: foetal (9-birth)
Pre-Embryonic period is divided into 2 stages, what are these?
What occurs in each?
Zygotic stage: is formed when the male gamete (sperm) and female gamete (egg) fuse.
Blastocyst stage: The single-celled zygote begins to divide into a solid ball of cells. Then, it becomes a hollow ball of cells called a blastocyst, attaching to the lining of the mother’s uterus.
What happens during the Embryonic period?
“organogenesis” Start of the organs developing from 2 weeks to 2months
Embryo undergoes intense morphogenesis & differentiation
There is little weight gain, it is mainly placental growth
What happens during the Foetal period?
Weeks 9-40 -> Refinement in structure and function and rapid growth period
Early fetus begins protein deposition
Late fetus begins adipose deposition
Describe growth velocity during development?
Describe weight changes during development?
Growth velocity is very small during the pre-embryonic and embryonic periods and increases rapidly during the foetal period
During the embryonic period weight gain is slow but increases rapidly in the foetal period
Initially protein accounts for most of this weight gain until after week 28 when foetal adipose tissue is laid down in subcutaneous and abdominal stores
When is a foetus is regarded as having a “growth restriction”
If his/her estimated weight is below the 10th percentile for his gestational age
What are the 2 main types of growth restriction?
1) Symmetrical: growth restriction is generalised and proportional
2) Asymmetrical: abdominal growth lags and there is relative sparing of head growth.
(2) tends to occur in the last part of pregnancy when maternal, foetal or utero- placental factors cause some deprivation of nutritional and oxygen supply to the foetus.
Sperm and egg combined to form a single cell called a ______ and the germinal stage of development commences
The germinal stage takes around 10 days. During this stage, the zygote begins to divide, in a process called ______.
This forms a ______ which attaches to the lining of the uterus around 6 days after fertilization. This process is called _______, is completed by day 9 or 10.
1) zygote
2) cleavage
3) blastocyst
4) implantation
What are the 3 basic germ layers?
What does each go on to become?
1) Endoderm: Digestive system, liver, pancreas, Lungs (inner)
2) Mesoderm: Circulatory system, skeletal system, muscular system, Lungs (epithelial layer)
3) Ectoderm: Hair, nails, skin, Nervous system
The lungs are derived from 2 embryological layers, what are these?
Endoderm forms the inner portion of the lungs
Mesoderm forms the epithelial covering of the lungs
What are the components of the support system of the embryo? (3)
- umbilical chord
- amnion
- placenta
Define organogenesis?
the process of organ formation during the first 2 months of pre-natal development
What are the 2 processes of foetal growth?
1) Rapid growth (increase in size and cell number)
2) continued tissue and organ differentiation (specialisation of cells to perform distant functions)
What are the timelines that define the following:
- Embryo
- Fetus
- Newborn
- Embryo 2-8 weeks after fertilization
- Fetus 8 weeks to birth
- Newborn first 24hours of Life
What are the timelines that define the following:
- Neonate
- Term Neonate
- Preterm, very preterm and extremely preterm
- Neonate from birth to 4 weeks
- Term Neonate 37weeks to 42 weeks
- Preterm <37 weeks.
(very preterm 28 to 32 weeks) and (extremely preterm less than 28)
What is the average weight of a newborn?
What defines the following:
- low Birth Weight (LBW)
- very Low Birth weight
- high Birth weight, what is this known as?
Average weight = around 3500g (3.5kg)
Low Birth Weight (LBW) <2500grams
Very Low Birth weight (VLBW) 1500grams
High Birth weight > 4500g known as macrosomia
What are the timelines that define the following in postnatal development:
- Neonatal
- Infancy
- Childhood
- Puberty
- Young Adult
- Neonatal birth to 1 month
- Infancy 1 month to 2 years
- Childhood 2 years to puberty
- Puberty 12 years to mid-teens
Young Adult is a new category (late teens to early twenties)
List 2 causes of a large birth weight
List 2 causes of low birth weight
Large:
1) Diabetes
2) Obesity
Low:
1) premature birth
2) suffered growth restriction
3) exposure to infection
List 3 ways we can determine Foetal development with examples
1) By duration of pregnancy:
- Fertilisation age
- Mothers last mensural period
2) By developmental criteria:
- Ultrasound ➞ crown-rump, foot length, biparietal diameter of head
- After birth ➞ weight at delivery, appearance after delivery
3) By symphysis- Fundal height
- distance between symphysis pubis to top of uterus
How is the last mensural period used to estimate foetal age?
Why may this be inaccurate?
A pregnancy wheel (a gestation calculator) uses last menstrual period to help determine your due date.
EDD is calculated by adding 280 days (40 weeks) to the first day of the last menstrual period
Gestational age is the age of the pregnancy from the last normal menstrual period (LMP), foetal age is the actual age of the growing baby
May be inaccurate due to:
- irregular cycles
- whether calendar months used
How can we use an ultrasound to estimate the foetal age?
At what week is this measurement performed?
Use Crown-rump length (CRL): measurement of the length of foetus from the top of the head (crown) to the bottom of the buttocks (rump).
Measured between 7-13 weeks to date the pregnancy and estimate EDD
List 3 other things an ultrasound be used to find out?
When is this test routinely carried out?
Ectopic pregnancies
Number of foetuses
Foetal anomalies
Routinely carried out at ~20 weeks
What is the Biparietal diameter? (BPD)
When is it used and what for?
The distance between the parietal bones of the foetal skull
Used in combination with other measurements to date
pregnancies in T2 & T3
List another measurement we can do?
How is this useful?
Abdominal circumference & femur length
AC & FL used in combination with BPD for dating and growth monitoring
Also useful for anomaly detection
What are the 2 ways we can estimate Symphysis- fundal height using the mother?
Which is more accurate?
1) Measuring tape (more accurate): measure mothers belly from top of uterus to top of pubic bone (distance between symphysis pubis to top of uterus)
2) The finger method (less accurate)
When using the Symphysis- fundal height (using the mother) where is the uterus located during the following timelines:
12-14 weeks
20-22 weeks
36-40 weeks
Weeks 12-14: top of uterus is right above pubic bone level
Weeks 20-22: top of uterus is at the level of belly button
Weeks 36-40: top of uterus is right under the ribs, as baby drops lower into the pelvis the top of uterus regresses by ~4cm
What are the timelines for the 3 trimesters of pregnancy?
T1: week 1 to the end of week 12
T2: week 13 to the end of week 26
T3: week 27 to the end of the pregnancy
What is Nuchal translucency (NT) and what is it used for?
Nuchal translucency (NT) is the sonographic appearance of a collection of fluid under the skin behind the foetal neck in the first-trimester of pregnancy
Detects chromosomal abnormalities
Describe the combined test and when it is used
The ‘combined test’ (triple test) comprises of
- nuchal translucency
- beta-human chorionic gonadotrophin
- pregnancy associated plasma protein- A
Offered to screen for Down’s syndrome in week 11
The quadruple test should be offered during week 15 weeks
When should females be offered an early ultrasound scan and what will this detect?
Pregnant women should be offered an early ultrasound scan between 10 weeks and 13 weeks 6 days
Determines gestational age and to detect multiple pregnancies
Give 4 pieces of lifestyle advice a doctor could give a pregnant mother
- vitamin D supplementation
- Folic acid
- Alcohol, smoking, recreational drugs
- exercise, including pelvic floor exercises
Why should pregnant women be given advice on the following foods
no eating pâté
not eating uncooked/undercooked ready-prepared meals/eggs
drinking only pasteurized or UTH milk
not eating ripened soft cheese
To reduce the risk of listeriosis: bacterial infection caused by Listeria monocytogenes
Give 3 reasons why monitoring foetal growth is so important
1) identify if they are at an increased risk of associated morbidity and mortality
2) detection of chromosomal abnormalities
3) identify potential birth complications eg. Macrosomia
