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Repro > Session 7 - Fetal physiology / growth > Flashcards

Session 7 - Fetal physiology / growth Flashcards

1
Q

Describe the double Bohr effect

A

Bohr effect is lower pH giving up oxygen more easily
Baby has higher CO2 than mother so at maternal blood lakes the fetus puts its CO2 in there
This means maternal RBCs will now give up their oxygen for fetus
Fetal CO2 has now become lower so have increased affinity for O2

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2
Q

Why is it useful for the mother to have respiratory alkalosis

A

Increased 2,3 BPG so give up oxygen more easily to fetus

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3
Q

Describe the double Haldane effect

A

Haldane affect is O2 affecting affinity of CO2
So M offloads O2 at baths, so can now take up CO2 fetus delivers
Fetus takes up o2 and will have less affinity for CO2 so it will leave

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4
Q

Compare contrast Bohr and Haldane effect

A

Bohr effect: Co2 affects the affinity of Hb for O2

Haldane effect: O2 affects the affinity of Hb for CO2

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5
Q

Fetal CO2 >/ < maternal Co2

A

Fetal co2 is higher

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6
Q

Fetal 02 >/< maternal O2

A

Fetal o2 lower

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7
Q

What is all that separates maternal blood from fetal capillaries

A

syncytiotrophoblast

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8
Q

what is fetal pO2

A

4kPa (adult is 11-13 kPa)

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9
Q

How does the fetus get the oxygen it needs?

A

HbF, double bohr and haldane, maternal respiratory aklalosis, mumma has increased haematocrit

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10
Q

What’s weird about fetal vagus nerve responses

A

If hypoxic, fetal HR slows!

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11
Q

What factor is important for fetal growth

A

IGF

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12
Q

Describe fetal growth in weeks in terms of hyperplasia/hypertrophy

A

Hyperplasia 0-20wks, hyperplasia +++ 20-28, 28-term is hypertrophy

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13
Q

First bowel movement is called

A

Meconium

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14
Q

How does the fetus handle bilirubin

A

It can’t really because it can’t conjugate so the placenta does it (that’s why physiological jaundice is common as the fetus has a lag in taking over)

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15
Q

What is normal, LBW, and macrosomic birth weight?

A

normal 2500g, macrosomic 4500g, LBW <2500g

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16
Q

When does CRL rapidly increase

A

In pre-embryonic and embryonic period

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17
Q

When does weight and growth rapidly increase

A

In foetal period (9-38)

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18
Q

From when can fetal movements be felt

A

Week 17

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19
Q

What do you use to measure fetal growth in different week periods

A

If 7-13 then CRL, if second or third trimester then measure femur length or biparietal diameter or abdominal circumference

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20
Q

Causes of oligohydramnios and polyhydramnios

A

Oligo- kidney problems, ureter problems

Poly- dysphagia, CNS problem, blind oesophagus, duodenal atresia, maternal hypertension

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21
Q

Three stages of fetal lung development with weeks

A

8-16: pseudoglandular (bronchioles formed)
16-24: canalicular (respiratory bronchioles formed)
24-term: terminal sac stage

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22
Q

What can you give to mother to increase surfactant in fetus

A

Glucocorticoids

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23
Q

What is the first system to start developing and the last to finish

A

Nervous system

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24
Q

When are coordinated voluntary movements possible?

A

Week 16

25
Q

When is the spinal cord myelinated

A

Week 20

26
Q

When is the brain myelinated

A

Week 36

27
Q

Why are gryi and sulci formed and at what week

A

Because brain grows more than skull, week 28

28
Q

What is quickening

A

Maternal awareness of fetal movements from week 17

29
Q

What do you use transvaginal US for

A

Checking for ectopics or early pregnancy loss (empty sac, no heart activity), can see heart beat from 5-6weeks (whereas USS only 10weeks for heart, 20weeks with stethoscope)

30
Q

Average HR at term

A

110-160bpm

31
Q

What is the Bio-Physical Profile?

A

Measures 5 facets of fetal development using USS and ECG. Looks at fetal movements, fetal breathing movements, HR, amniotic fluid volume, fetal tone (flexion or extension)

32
Q

Tell me about the non-stress test

A

Fetal HR should increase after fetal movements. Measure for 30 mins and see 3 increased HRs following movement. Test is either reassuring or non-reassuring, not necessarily worrying

33
Q

Describe the two types of growth restriction that occur in different stages of pregnancy

A

In early pregnancy you get symmetrical growth restriction, in late pregnancy asymmetrical growth restriction because the head has already done most of its growing but the abdomen is supposed to grow in this bit (so normal head, small abdo)

34
Q

Oligohydramnios is associated with what type of growth restriction

A

Asymmetrical

Also associated with premature membrane rupture and bladder obstruction

35
Q

What would make a fetus “at risk”

A

cardiac anomaly, unexplained polyhydramnios, chromosome abnormalities

36
Q

What can the fetus put in the amniotic fluid in response to stress or asphyxia

A

Meconium

37
Q

How should you monitor fetal HR in labour

A

Scalp electrode

38
Q

What are the key hormones needed for labour

A

So prostaglandins increase intracellular Ca2+ and increase myometrial gap junctions. Basically preparing the uterine muscle to contract.
Oxytocin works synergistically with prostaglandins, increases intracellular Ca2+ and gap junctions

39
Q

When does oxytocin production start to increase

A

Second half of pregnancy

40
Q

When does prostaglandin production start to increase

A

Locally produced in labour, stimulated by oxytocin to be released

41
Q

How is oestrogen involved with the role of prostaglandins and oxytocin

A

Increases contraction related proteins e.g. myometrial receptors for oxytocin and prostaglandin

42
Q

What initiates labour

A

Prostaglandins with membrane rupture

43
Q

What induces cervical ripening and how

A

Prostaglandins reduce collagen, increase glycosaminoglucans and hylauronic acid
Relaxin also causes cervical ripening

44
Q

Ferguson reflex

A

As contractions increase they get more often and stronger
Sensory receptors in the cervix and vagina are stimulated by contractions; excitation passes via afferent
nerves to the hypothalamus, promoting massive oxytocin release. This ‘positive feedback’ makes
contractions more forceful and frequent

45
Q

What is brachystasis

A

Myometrium is special. At each contraction muscle fibres shorten, but do not relax fully. The uterus, particularly the fundal region therefore shortens progressively

46
Q

What is the size of the birth canal determined by

A

The pelvic inlet

47
Q

Three stages of labour

A
  1. Creation of birth canal, ends when 10cm dilated
  2. Begins once cervix is 10cm dilated, ends with delivery of fetus
  3. Placenta and membrane expelled, normally within ten minutes
48
Q

How should the fetus present?

A

Should be a vertex presentation (occiput leading), longitudinal lie, flexion attitude

49
Q

What can we give to help induce labour

A

Synthetic PGs, oxytocin, anti-progesterone, stimulate PGs with membrane rupture

50
Q

How is maternal blood loss limited post partum

A

Living ligatures contract (myometrial blood vs are constricted by uterine contractions)
Contraction and retraction of uterus makes placental site smaller so helps with placental separation
Thrombosis of torn vessels and sinuses

51
Q

How is the breathing environment different to the baby once it’s born

A

Pulmonary vascular resistance is lower

O2 is much higher

52
Q

What happens with baby’s first breath

A

Pulmonary vascular resistance is now much lower so blood flows to lungs/more blood enters LA and less in RA, closes foramen ovale

53
Q

Mammary glands are derived from

A

Ectoderm

54
Q

Describe breast growth at different stages

A

Oestrogen from ovaries at puberty stimulates lactiferous duct growth
Post-menarche progesterone induces further lactiferous duct growth and also starts development of lobules at the end of ducts
At pregnancy hCG induces rapid growth and branching of terminal portions of lobules, vascularity increases +++
At 8 weeks sustained progesterone completes alveolar differentiation
At 12 weeks alveolar secretions
At 24weeks secretions are Ig rich

55
Q

Why is there no lactation before birth

A

Because even though prolactin is rising (and hcG/progesterone have developed boobs) oestrogen from placenta is inhibiting prolactin

56
Q

Describe milk let down

A

Nipple sensory - hypothalamus - oxytocin released from ant pit - myoepithelial cells lining milk duct contract to let milk out

57
Q

What does prolactin do in terms of lactation

A

DOESN’T control milk let down but does induce milk formation for NEXT feed

58
Q

Why do periods take a while to come back after birth

A

Sucking inhibits GnRH

59
Q

How does lactation end

A

If sucking stops then oxytocin won’t be released so will stop releasing milk
Plus prolactin levels fall over time so will stop making milk

Repro (10 decks)

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