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Repro > Foetal physiology, growth and development > Flashcards

Foetal physiology, growth and development Flashcards

1
Q

Why does O2 move from mum to baby at the placenta effectively? (5)

A
  • Fetal blood has low pO2- diffusion gradient
  • fetal Hb is made of 2 alpha and 2 gamma subunits- higher affinity
  • double bohr effect
  • increased maternal production of 2,3 BPG secondary to physiological respiratory alkalosis means her Hb is low affinity
  • double haldane effect
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2
Q

What is the double bohr effect?

A

Progesterone= hyperventilation = low pCO2= CO2 entering maternal blood= pH drop= T state= lower affinity for O2= O2 moves to fetus.
Also, CO2 lost from fetal circulation= increase pH= R state= increased affinity for O2

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3
Q

What is the haldane effect?

A

The Hb in mother gives up more O2 so can accept increasing CO2. Hb on fetus accepts more O2 so gives up Co2. This means no alterations in local pCO2

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4
Q

Describe the fetal circulation

A
  • Most blood in RA passes into LA via foramen ovale
  • Some blood however goes into RV, it passes into the pulmonary artery but from here bypasses lungs and goes into aorta via ductus arteriosus
  • The blood travels round the body, then goes to the placenta via the umbilical arteries (low pO2)
  • Umbillical veins leave placenta, bipasses liver via the ductus venosus and enters back into the IVC
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5
Q

How does the fetus respond to hypoxia? (2)

A
  • Resdistributes blood flow to heart and brain
  • Slows down heart rate to reduce O2 demand (chemoreceptors detect drop in pO2 but stimulate rather than inhibit the vagus nerve)
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6
Q

What is a normal HR for a fetus?

A

120-160 BPM

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7
Q

How can a foetuses HR be measured? (3)

A
  • ultrasound at 5-6 weeks
  • doppler stethoscope at 8 weeks
  • normal stethoscope at 20 weeks
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8
Q

How much amniotic fluid is normal at 38 weeks?

A

1L

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9
Q

How is amniotic fluid recycled?

A

Some is swallowed as it practices swallowing, some is inhaled as it practices breathing, some it absorbed through skin. It is then absorbed and excreted again.

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10
Q

What is amniotic fluid made of?

A

98% is water. It also contains electrolytes, creatine, urea, bile, renin, glucose, hormones and cells.

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11
Q

What is the vernic caseosa?

A

A waxy covering which protects the foetuses skin from amniotic fluid.

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12
Q

What happens to debris from swallowng amniotic fluid which cannot be absorbed

A

It is called muconium, it cannot be directly excreted until birth. It accumulates and in the foetuses GI tract and is passes as its first poo

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13
Q

Which can be done first, choriocentesis or amniocentesis?

A

choriocentesis

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14
Q

Why do some babies get jaundice after birth?

A

some times takes a while for their liver to develop the ability to conjugate bilirubin

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15
Q

What hormones are needed for fetal growth, which are specific to the 1st and 2nd trimester?

A

insulin, EGF, TGFa and leptin (from placenta) always needed.
IDF2 is nutrient independant and seen in trimester 1
IDF1 is nutrient dependant seen in trimester2

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16
Q

What is meant by asymetrical growth restriction?

A

The baby is disproportionate (head proportionally larger than abdomen)

17
Q

When does malnutrition have to occur to cause symetrical and asymetrical growth restriction?

A

If early on= symetrical growth restriction (reversible).

If later= asymetrical

18
Q

What may cause asymetrical growth restriction?

A
  • maternal factors (malnutrition, smoking ect) later in pregnancy
  • Uteroplacental insufficiency (placenta poorly effective
  • genetic disorders
  • preeclampsia
  • preterm birth
19
Q

What may cause symetrical growth restriction

A
  • extreame fetal malnourishment
  • environmental toxins (maternal substance abuse)
  • genetic disorders
  • congenital infections
  • anaemia
  • preterm birth
  • may just be a small baby (small mum inc likelyhood)
20
Q

What is the fundal height at 12 weeks, 16 weeks, 20 weeks and 36 weeks?

A

12 weeks= pubic symphysis
16 weeks= between pubic symphysis and umbilicus
20 weeks= umbilicus
36 weeks= xiphisternum

21
Q

How does rate and type of growth change?

A

Embryonic period= hyperplasia, lots of activity but not much absolute growth
Fetal period= hypertrophy and some hyperplasia= lots of absolute growth
Head grows first- taking up 1/2 total body length, eventually the body catches up until head only takes up 1/4 total body length

22
Q

What should be reported at a normal 20 week scan? (4)

A
  • mother felt baby moving
  • heartbeat can be heard w/ normal stethoscope
  • structures big enough to be seen w/ ultrasound and check theyre developing normally
  • can asses age of fetus accuratly by looking at crown- rump length
23
Q

Why is time since last menses an inaccurate way to asses fetal age?

A

Irregular cycles

24
Q

How can fetal age be assesed in the 2nd or 3rd trimester?

A
  • crown- rump length

- biparietal diameter (distance between the two parietal bones)

25
Q

Define macro and microsomia

A 
Microsomia= birthweight< 2500g
Macrosomia= birthweight > 4000g
26
Q

What may cause macrosomia?

A

Gestational diabetes
large parents
constiutionally large

27
Q

Describe the development of the respiratory system

A

Starts as diverticulum growing out from foregut at 8-16 weeks. At 16-26 weeks they bud and form bronchioles and the tracheosphageal septum starts to appear. By 26 weeks the respiratory bronchioles appear, the trachea and oesphagus are completely seperated and the type 1 and 2 pneumocytes start to develop.

28
Q

How can respiratory distress be prevented in babies which have to be born prematurely.

A

Glucocorticoid treatment before birth, should increase surfacant production

29
Q

When does the kidney start to develop and what does it do in the foetus?

A

at the 10th week, it filters urine but doesnt perform other functions of the kidneys

30
Q

Why is a baby less than 4 months old uncoordinated?

A

Corticospinal tracts are needed to coordinate voluntary movements but these dont develop till the baby is 4

31
Q

when does myelination of the brain occur?

A

In the 9th month of pregnancy

32
Q

When do motor and sensory systems start to develop?

A

from 8 weeks, this allows the baby to practise movements such as sucking and breathing. the mother becomes aware of these movements from about 17 weeks

33
Q

How can fetal development be assessed?

A
  • Amniotic fluid volume (monitors placenta, kidneys, MSK and CNS ect)
  • fetal movement (monitors CNS and MSK)
  • fetal breathing movements (resp, CNS, MSK)
  • heart rate response to non stress test (autonomics, CVS)
34
Q

What may cause olihydramnios (low amniotic fluid volume)

A

Placental insufficiency, fetal renal impariment, maternal hypertensive disorders, fetal bladder outlet obstruction, premature rupture of membranes

35
Q

What may cause polyhydramnios (high amniotic fluid volume)? (2)

A

inability to swallow, idiopathic

36
Q

What is normal fetal pO2?

A

4pka

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