12. Fetal Growth And Development

Question 1

When is the embryonic period and what happens in it?

Answer 1

Weeks 3-8.

Creation of structures - organogenetic period. Absolute growth is very small. Placental growth is great.

Question 2

When is the fetal period and what happens in it?

Answer 2

Weeks 9-38.
Growth and physiological maturation of the structures created in the embryonic period. Is the period involving preparation for the transition to independent life after birth. Growth and weight gain is rapid.

Question 3

When does crown-rump length of a fetus increase, and when is weight gain occur?

Answer 3

CRL - increases rapidly in pre-embryonic, embryonic and early fetal periods.
Weight gain - slow at first, increases rapidly in mid and late fetal periods.

Question 4

When is protein deposition most significant in the fetus?

Answer 4

Early fetus.

Question 5

When is adipose deposition most prominent in the fetus?

Answer 5

Late fetus.

Question 6

What is the head to body ratio in a fetus at 9 weeks and what happens there after?

Answer 6

9 weeks - head is approximately half the crown rump length.

Thereafter, the body length and lower limb growth accelerates.

Question 7

Give 3 ante-natal assessments of fetal well-being that are non-invasive

Answer 7

Asking mother about fetal movements (reveal foetuses requiring follow-up).
Symphysis-fundal height.
USS.

Question 8

When is an ultrasound can routinely carried out in pregnancy and why?

Answer 8

20 weeks.

To assess fetal growth and anomalies (everything is developed and big enough to see).

Question 9

Why might an ultrasound scan be carried out early in a pregnancy?

Answer 9

Calculate age.
Rule out ectopic pregnancy.
Check number of foetuses.

Question 10

Why can using the date of the last menstrual period of a pregnant woman be inaccurate in estimating fatal age?

Answer 10

Woman may have an irregular menstrual cycle.

Question 11

What is an accurate way to estimate fetal age using an ultrasound scan?

Answer 11

Using developmental criteria, and measuring crown-rump length (between 7 and 13 weeks).

Question 12

What is biparietal diameter?

Answer 12

Distance between the parietal bones of the fetal skull.

Question 13

What is biparietal diameter and what can it be used in combination with?

Answer 13

Used in combination with abdominal circumference and femur length to date pregnancies in the second and third trimester. Also sued for gro

Question 14

Which is considered the average birth-weight, and so what weigh suggests growth restriction and what is macrosomia?

Answer 14

3500g average.
<2500g growth restriction.
>4500g macrosomia.
But many factors influence birth weight eg number of weeks born at, so not all pathological.

Question 15

What causes macrosomia?

Answer 15

Maternal diabetes.

Question 16

Why is accurate dating of a pregnancy important?

Answer 16

If baby is born with a low weight, allows you to tell if is because they are premature, constitutionally small (small mother=small baby), or have suffered growth restriction.

Question 17

Why is it important to be able to tell if a baby has suffered growth restriction?

Answer 17

Is associated with neonatal morbidity and mortality?

Question 18

What happens in the pseudoglandular stage (weeks 8-16) of the lung development in a fetus?

Answer 18

Duct system begins to form within the bronchopulmonary segments created during the embryonic period (when the respiratory diverticulum is formed from the foregut - bronchopulmonary tree).

Question 19

What happens in the canalicular stage (weeks 16-26) of the lung development in the fetus?

Answer 19

Formation of the respiratory bronchioles as budding from the bronchioles formed during the pseudoglandular stage.

Question 20

What happens in the terminal sac stage (weeks 26-term) of the lung development in the fetus?

Answer 20

Terminal sacs (alveoli) begin to bud from the respiratory bronchioles and differentiation of Type I and II pneumocytes which produce surfactant.

Question 21

What aids in the preparation of the lungs to take on gas exchange at birth, in the second and third trimesters?

Answer 21

Breathing movements for conditioning o the respiratory musculature.
Fluid filled.

Question 22

Development of what system and why determines the threshold of viability?

Answer 22

Development of the lungs - viability is only a possibility once the lungs have entered the terminal sac stage of development, ie after 24 weeks.

Question 23

When does respiratory distress occur and what causes it?

Answer 23

Often affects infants born prematurely, is due to insufficient surfactant production so lack of surface tension and alveoli collapse.

Question 24

What is used as treatment for respiratory distress syndrome if pre-term delivery is unavoidable or inevitable?

Answer 24

Glucocorticoid treatment of the mother which increases surfactant production in the fetus.

Question 25

What is the values definitive fetal heart rate, and when is it achieved?

Answer 25

110-160bpm.

Around 15 weeks.

Question 26

What happens to fetal heart rate in foetal distress and demise?

Answer 26

Fetal bradycardia.

Question 27

What is oligohydramnios and what causes it?

Answer 27

Too little amniotic fluid.
Placental insufficiency (last of nutrients), foetal renal impairment.

Question 28

Is kidney function necessary for survival in utero?

Answer 28

No - just leads to oligohydramnios.

Question 29

What is polyhydramnios and what causes it?

Answer 29

Too much amniotic fluid.
Caused by a foetal abnormality, eg inability to swallow (eg due to fistula or blind ending oesophagus or due to CN defect so unable to coordinate swallow).

Question 30

What system is the first to begin developing and last to finish developing?

Answer 30

Nervous system.

Question 31

When do the corticospinal tracts required for coordinated voluntary movements in a foetus start to form?

Answer 31

4th month.

Question 32

Why is there increasing infant mobility in the first year after birth?

Answer 32

Myelination of the brain only begins in the 9th month of gestation. So corticospinal tract myelinated is incomplete at birth, and as it develops, so does movement.

Question 33

Between which weeks of pregnancy does the fetus begin startle movements?

Answer 33

Weeks 8-10.

Question 34

Between which weeks of pregnancy does the fetus begin breathing movements?

Answer 34

10-12 weeks.

Question 35

Between which weeks of pregnancy does the fetus begin noncoordinated suckling movements 9eg sucking thumb)?

Answer 35

Weeks 13-16.

Question 36

What is quickening?

Answer 36

Maternal awareness of foetal movements from 17 weeks onwards.