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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?

25
When is the spinal cord myelinated
Week 20
26
When is the brain myelinated
Week 36
27
Why are gryi and sulci formed and at what week
Because brain grows more than skull, week 28
28
What is quickening
Maternal awareness of fetal movements from week 17
29
What do you use transvaginal US for
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
Average HR at term
110-160bpm
31
What is the Bio-Physical Profile?
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
Tell me about the non-stress test
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
Describe the two types of growth restriction that occur in different stages of pregnancy
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
Oligohydramnios is associated with what type of growth restriction
Asymmetrical | Also associated with premature membrane rupture and bladder obstruction
35
What would make a fetus "at risk"
cardiac anomaly, unexplained polyhydramnios, chromosome abnormalities
36
What can the fetus put in the amniotic fluid in response to stress or asphyxia
Meconium
37
How should you monitor fetal HR in labour
Scalp electrode
38
What are the key hormones needed for labour
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
When does oxytocin production start to increase
Second half of pregnancy
40
When does prostaglandin production start to increase
Locally produced in labour, stimulated by oxytocin to be released
41
How is oestrogen involved with the role of prostaglandins and oxytocin
Increases contraction related proteins e.g. myometrial receptors for oxytocin and prostaglandin
42
What initiates labour
Prostaglandins with membrane rupture
43
What induces cervical ripening and how
Prostaglandins reduce collagen, increase glycosaminoglucans and hylauronic acid Relaxin also causes cervical ripening
44
Ferguson reflex
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
What is brachystasis
Myometrium is special. At each contraction muscle fibres shorten, but do not relax fully. The uterus, particularly the fundal region therefore shortens progressively
46
What is the size of the birth canal determined by
The pelvic inlet
47
Three stages of labour
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
How should the fetus present?
Should be a vertex presentation (occiput leading), longitudinal lie, flexion attitude
49
What can we give to help induce labour
Synthetic PGs, oxytocin, anti-progesterone, stimulate PGs with membrane rupture
50
How is maternal blood loss limited post partum
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
How is the breathing environment different to the baby once it's born
Pulmonary vascular resistance is lower | O2 is much higher
52
What happens with baby's first breath
Pulmonary vascular resistance is now much lower so blood flows to lungs/more blood enters LA and less in RA, closes foramen ovale
53
Mammary glands are derived from
Ectoderm
54
Describe breast growth at different stages
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
Why is there no lactation before birth
Because even though prolactin is rising (and hcG/progesterone have developed boobs) oestrogen from placenta is inhibiting prolactin
56
Describe milk let down
Nipple sensory - hypothalamus - oxytocin released from ant pit - myoepithelial cells lining milk duct contract to let milk out
57
What does prolactin do in terms of lactation
DOESN'T control milk let down but does induce milk formation for NEXT feed
58
Why do periods take a while to come back after birth
Sucking inhibits GnRH
59
How does lactation end
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

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