Normal Foetal Growth And Development

Front 1

What are the complications of foetal growth restriction?
HHHie.

Back 1

Hypoxia
Hypothermia
Hypoglycaemia
Infection
NEC

Front 2

What are the long-term complications of foetal growth restriction?

Back 2

Hypertension
Cardiovascular disease
Diabetes

Front 3

What are the foetal influences on foetal growth?

Back 3

Genetic - chromosomal defects more likely to cause FGR; foetal sex, males > females.
Infection - rubella, cytomegalovirus, toxoplasma, syphilis.

Front 4

What are the physiological maternal influences on foetal growth?

Back 4

Normal: maternal height, pre-pregnancy weight, age, ethnic group.
Parity: increase = increased weight.
Teenage mothers more likely to have FGR babies.

Front 5

What are the behavioural maternal influences on foetal growth?

Back 5

Smoking, alcohol, drug use are all associated with FGR.

Front 6

What are the chronic disease influences on foetal growth?

Back 6

Chronic maternal disease may restrict foetal growth, usually through effect on placental function or by resulting in maternal hypoxia.
Hypertension.
Lung conditions - CF.
Cardiac conditions - cyanotic heart disease.
Maternal thrombophila.

Front 7

What are the placental influences on foetal growth?

Back 7

The placenta is the only way in which the foetus can receive oxygen and nutrients from the mother during pregnancy.
Placental infarction and separation can impair transfer.

Front 8

What is trisomy 13 called?

Back 8

Patau's syndrome.

Front 9

What is trisomy 18 called?

Back 9

Edward's syndrome.

Front 10

What are the four shunts in the foetal circulation?

Back 10

Umbilical circulation.
Ductus venosus.
Foramen ovale.
Ductus arteriosus.

Front 11

What is the ductus venosus? What is its purpose?

Back 11

The ductus venosus shunts blood from the umbilical vein directly to the inferior vena cava. This allows the bulk of the oxygenated blood to bypass the liver and join the IVC to go to the RA.

Front 12

What prevents the oxygenated blood from the umbilical vein that is shunted through the ductus venosus from mixing with the unoxygenated blood from the IVC?

Back 12

The ductus is a narrow vessel so there is a high blood velocity generated within it so the ductus venosus blood is "streaming". Also, there is a membranous valve in the RA, called the crista dividens, which also prevents them from mixing.

Front 13

What is the foramen ovale? What is its purpose?

Back 13

It is a phsiological defect in the atrial septum.
It allows oxygenate blood from the RA to pass straight into the LA. From here, blood passes through the mitral valve to the left ventricle and hence to the aorta.

Front 14

Where does most of the oxygenated blood in the foetal circulation go?

Back 14

50% goes to the head and upper extremities.
The remainder passes down the arota to mix with blood of reduced oxygen saturation from the right ventricle.

Front 15

What is the ductus arteriosus and what does it do?

Back 15

It connects the pulmonary artery with the descending aorta.
Allows deoxygenated blood that has returned from the head to flow through the RA and RV to bypass the lungs.
By this means the deoxygenated blood can travel down the aorta into the umbilical arterial circulation and return to the placenta for reoxygenation.

Front 16

What keeps the ductus patent prior to birth?

Back 16

The production of prostaglandins E2 and prostacyclins. These act as local vasodilators.

Front 17

What happens to the foetal shunts after birth?

Back 17

1. Cessation of umbilical blood flow.
2. Leads to cessation of flow in the ductus venosus.
3. Leads to fall in pressure in the right atrium.
4. Leads to closure of the foramen ovale.
5. Ductus arteriosus closes a few days after birth.

Front 18

What causes the pulmonary circulation to open after birth?

Back 18

Ventilation combined with a rapid fall inpulmonary vascular ristance.

Front 19

What can be the conseqeunce of a failed transition from foetal to adult circulation?

Back 19

Pulmonary vascular resistance may fail to fall despite adequate breathing.
LEADS TO --->
LtoR shunt of blood from aorta through the PDA into the lungs. Therefore babye is cyanosed and can suffer from hypoxia.
Can result in:
- pulmonary congestion
- NEC
- intraventricular haemorrhage

Front 20

When does the lung first appear?

Back 20

At 3 to 4 weeks post-conception as an outgrowth of the primitive foregut.

Front 21

What are the developments of the foetal lung:
a) by 20 weeks?
b) by 25 weeks?
c) by 30 weeks?

Back 21

a) conductive airway tree and vascular tree developed.
b) type I and II epithelial cells
c) surfactant production

Front 22

What is the foetal lung filled with?

Back 22

Fluid.
Begins to be produced during gestation.
At birth, production ceases and fluid is absorbed.
The clearance of fluid and the onset of breathing causes the resistance in the vascular bed to fall and results in an increased pulmonary blood flow.

Front 23

What is the importance of surfactant?

Back 23

Surfactant prevents the collapses of small alveoli during expiration by lowering surface tension. Inadequate amounts result in poor lung expansion and poor gas exchange.

Front 24

What is respiratory distress syndrome?

Back 24

Occurs in infants born pre-term prior to the maturation of the surfactant system.
Inadequate surfactant results in poor lung expansion and poor gas exchange.
RDS - present in the first few hours of life with tachypnoea and cyanosis. Occurs in 80% of babies born between 23 and 27 weeks.
Complications: hypoxia, asphyxia, IVH, NEC.
Can reduce incidence and severity by giving steroids antenatally to mothers at risk.

Front 25

Why is amniotic fluid important for lung maturation?

Back 25

Babies practice breathing during utero.
Oligohydraminos (reduced amniotic fluid) can result in pulmonary hypoplasia. Leads to progressive respiratory failure from birth.

Front 26

What does the foregut endoderm give rise to?

Back 26

Oesophagus, stomach, proximal half of duodenum, liver, pancreas.

Front 27

What does the midgut endoderm give rise to?

Back 27

Distal half of the duodenum, jejunum, ileum, caecum, appendix, ascending colon, transverse colon.

Front 28

What does the hindgut endoderm give rise to?

Back 28

Descending colon, sigmoid colon, rectum.

Front 29

What is the point of the physiological hernia?

Back 29

During weeks 5/6, there isn't enough room for the midgut to develop inside the abdomen, so it is extruded into the umbilical cord as a hernia.
It undergoes rotation prior to re-entering the abdominal cavity by 12 weeks.

Front 30

What is an omphalocele?

Back 30

Failure of the gut to re-enter the abdominal cavity.

Front 31

What is an atresia in relation to the gut?

Back 31

These exist when there is a segment of bowel in which the lumen is not patent, e.g. the oesophagus or duodenum.
As the foetus continually swallows amniotic fluid, any obstruction which prevents this will cause polyhydramnios.

Front 32

What is the most common fistula?

Back 32

TOF - trache-oesophageal fistula.
A connection exists between the trachea and oesophagus. Causes air to pass into the stomach or swallowed milk and stomach acid to pass into the lungs. Needs surgical intervention.

Front 33

What is VACTERL?

Back 33

A collection of congenital anomalies.
Vertebral.
Anal.
Cardiac.
Tracheal.
Esophageal.
Rectal.
Limb.

Front 34

When does peristalsis begin in utero?

Back 34

During the second trimester.
The large bowel is filled with meconium at term.

Front 35

When does the foetus greatly increased its fat stores?

Back 35

During the last trimester.
Therefore, preterm infants have virtually no fat.

Front 36

Why are growth restricted foetuses more likely to have hypoglycaemia?

Back 36

Because they have reduced glycogen stores.

Front 37

What do the pancreas, liver and gall bladder develop from?

Back 37

The endoderm of the foregut.
Liver and biliary tree - 3/4 weeks.

Front 38

When does the liver begin to perform haematopoiesis?

Back 38

By the sixth week.
Peeks at 12 - 16 weeks.
Continues until gestation.

Front 39

What happens to unconjugated bilirubin in utero?

Back 39

It is actively transported from foetus to mother. Only a small amount is conjugated by the liver and secreted in bile.

Front 40

What do infants sometimes get physiological jaundice?

Back 40

Because of the loss of the placental route of excretion of unconjugated bilirubin.
May result in unconjugated hyperbilirubinaemia, especially in preterm infants.

Front 41

What are the two primitive forms of the kidney?

Back 41

Pronephros, mesonephros.
Pronephros develops first into ducts. Induces the production of the mesonephros. Pronephros degenerates. Mesonephric (Wolffian) duct contnues to extend.

Front 42

What does the uretic bud develop from, when, and into?

Back 42

Ureteric bud develops as an out-pouching from the Wolffian duct during the fifth week of gestation. It will branch out to from the collecting duct system and the renal secretory system.

Front 43

When are the ureteric bud and the nephronic units formed by?

Back 43

32 - 36 weeks gestation. However, not yet mature. Maturity continues after birth.

Front 44

What is the importance of foetal urine?

Back 44

It forms much of the amniotic fluid. If there is renal agenesis, this will cause a severe reduction in amniotic fluid.

Front 45

What is Potter's syndrome?

Back 45

Babies born with bilateral renal agenesis develop Potter's syndrome due to the oligohydramnios. Features include:
- widely spaced eyes
- low set ears
- don't pass urine
Usually die due to renal failure or pulmonary hypolasia.

Front 46

Where are the most common sites of congenital urinary tract obstruction?

Back 46

Pyeloureteric junction.
Vesicoureteric junction.
Posterior urethral valves.

Front 47

What is the vernix?

Back 47

It is the outer layer of the ectoderm, the periderm, which forms at 6 weeks. The periderm eventually sloughs to become the vernix, a creamy protective coat that covers the skin of the foetus.

Front 48

What happens to preterm babies with no vernix?

Back 48

No vernix and thin skin allows a large amount of insensible water loss.

Front 49

Which immunoglobulin crosses the placenta?

Back 49

IgG. Provides passive immunity to the foetus and the neonate.

Front 50

When does the foetal heart begin to beat?

Back 50

At 7 to 8 weeks.

Front 51

When does the amnion contact the chorion?

Back 51

By 12 weeks gestation.
The two membranes become adherent but they never fuse.

Front 52

What are the four functions of the amniotic fluid?

Back 52

1. Protect the foetus from mechanical injury.
2. Permit movement of the foetus while preventing limb contracture.
3. Prevent adhesions between foetus and amnion.
4. Permit foetal lung development.

Front 53

What are some causes of oligohydramnios?

Back 53

Renal agenesis.
Cystic kidneys.
FGR.

Front 54

What are some causes of polyhydramnios?

Back 54

Anencephaly.
Oesophageal/duodenal atresia.
This is because they cause reduced removal of fluid.