7.1 Foetal growth and development

Question 1

How long does an unborn baby spend in the uterus?

What is the average length of pregnancy?

Answer 1

38weeks

40weeks

Question 2

When do we count the first day of pregnancy?

Answer 2

Pregnancy is counted from the first day of the woman’s last period (NOT the date of conception which generally occurs two weeks later)

Question 3

What are the 3 stages that occur from fertilisation to birth?
What weeks do these occur between?

Answer 3

A: pre-embryonic/ germinal (0-2w)
B: embryonic (3-8w)
C: foetal (9-birth)

Question 4

Pre-Embryonic period is divided into 2 stages, what are these?
What occurs in each?

Answer 4

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.

Question 5

What happens during the Embryonic period?

Answer 5

“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

Question 6

What happens during the Foetal period?

Answer 6

Weeks 9-40 -> Refinement in structure and function and rapid growth period

Early fetus begins protein deposition

Late fetus begins adipose deposition

Question 7

Describe growth velocity during development?

Describe weight changes during development?

Answer 7

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

Question 8

When is a foetus is regarded as having a “growth restriction”

Answer 8

If his/her estimated weight is below the 10th percentile for his gestational age

Question 9

What are the 2 main types of growth restriction?

Answer 9

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.

Question 10

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.

Answer 10

1) zygote
2) cleavage
3) blastocyst
4) implantation

Question 11

What are the 3 basic germ layers?

What does each go on to become?

Answer 11

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

Question 12

The lungs are derived from 2 embryological layers, what are these?

Answer 12

Endoderm forms the inner portion of the lungs

Mesoderm forms the epithelial covering of the lungs

Question 13

What are the components of the support system of the embryo? (3)

Answer 13

• umbilical chord
• amnion
• placenta

Question 14

Define organogenesis?

Answer 14

the process of organ formation during the first 2 months of pre-natal development

Question 15

What are the 2 processes of foetal growth?

Answer 15

1) Rapid growth (increase in size and cell number)

2) continued tissue and organ differentiation (specialisation of cells to perform distant functions)

Question 16

What are the timelines that define the following:

• Embryo
• Fetus
• Newborn

Answer 16

• Embryo 2-8 weeks after fertilization
• Fetus 8 weeks to birth
• Newborn first 24hours of Life

Question 17

What are the timelines that define the following:

• Neonate
• Term Neonate
• Preterm, very preterm and extremely preterm

Answer 17

• 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)

Question 18

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?

Answer 18

Average weight = around 3500g (3.5kg)

Low Birth Weight (LBW) <2500grams

Very Low Birth weight (VLBW) 1500grams

High Birth weight > 4500g known as macrosomia

Question 19

What are the timelines that define the following in postnatal development:

• Neonatal
• Infancy
• Childhood
• Puberty
• Young Adult

Answer 19

• 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)

Question 20

List 2 causes of a large birth weight

List 2 causes of low birth weight

Answer 20

Large:

1) Diabetes
2) Obesity

Low:

1) premature birth
2) suffered growth restriction
3) exposure to infection

Question 21

List 3 ways we can determine Foetal development with examples

Answer 21

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

Question 22

How is the last mensural period used to estimate foetal age?

Why may this be inaccurate?

Answer 22

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

Question 23

How can we use an ultrasound to estimate the foetal age?

At what week is this measurement performed?

Answer 23

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

Question 24

List 3 other things an ultrasound be used to find out?

When is this test routinely carried out?

Answer 24

Ectopic pregnancies
Number of foetuses
Foetal anomalies

Routinely carried out at ~20 weeks

Question 25

What is the Biparietal diameter? (BPD)

When is it used and what for?

Answer 25

The distance between the parietal bones of the foetal skull

Used in combination with other measurements to date
pregnancies in T2 & T3

Question 26

List another measurement we can do?

How is this useful?

Answer 26

Abdominal circumference & femur length

AC & FL used in combination with BPD for dating and growth monitoring

Also useful for anomaly detection

Question 27

What are the 2 ways we can estimate Symphysis- fundal height using the mother?

Which is more accurate?

Answer 27

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)

Question 28

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

Answer 28

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

Question 29

What are the timelines for the 3 trimesters of pregnancy?

Answer 29

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

Question 30

What is Nuchal translucency (NT) and what is it used for?

Answer 30

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

Question 31

Describe the combined test and when it is used

Answer 31

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

Question 32

When should females be offered an early ultrasound scan and what will this detect?

Answer 32

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

Question 33

Give 4 pieces of lifestyle advice a doctor could give a pregnant mother

Answer 33

• vitamin D supplementation
• Folic acid
• Alcohol, smoking, recreational drugs
• exercise, including pelvic floor exercises

Question 34

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

Answer 34

To reduce the risk of listeriosis: bacterial infection caused by Listeria monocytogenes

Question 35

Give 3 reasons why monitoring foetal growth is so important

Answer 35

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