Session 9- The fetus Flashcards

1
Q

how does the mother compensate for the low partial pressure of oxygen

A

progesterone causes physiological hyperventilation which results in the mother developing a physiological respiratory alkalosis- this also means there will be a lower conc of aCo2 in maternal blood setting up a gradient for gas exchange

increased maternal dpg to reduce materal affinity for o2

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2
Q

what is HbF comprised of

A

2 alpha

2 gamma

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3
Q

why does HbF have a higher affinity for o2

A

it doesnt bind 2,3 BPG as maternal Hb does

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4
Q

what is the double Bohr effect

A

as co2 passes into the intervillous blood the pH will decrease causing decreased affinity for oxyen for the mother

the fetus will be giving up Co2 dur to the gradient of transfer causing increased pH which results in increased affinty for oxygen

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5
Q

what is the double haldene effect

A

as maternal Hb gives up o2 it can accept increasing amounts of Co2

the fetal Hb gives up more Co2 as o2 is accepted

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6
Q

why causes fetal distress

A

a possible fetal response to hypoxia is bradycardia via vagal stimulation to try and reduce he o2 demand required by the heart

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7
Q

how can smoking affect blood oxygen levels

A

can cause chronic hypoxaemia which could lead to intruterine growth restriction

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8
Q

where does ductus venosus shunt and why

A

blood from umbilical vein to IVC to prevent blood going to the liver to maintain a high level of o2 in circulation that will be arriving to the brain

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9
Q

where does foramen ocale shunt

A

allows most of the blood to travel from right atrium to left atrium and a small amount goes to right ventricle mixing with blood from SVC

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10
Q

what hormones are neccesary for fetal growth

A

insulin

IGFI- nutrient infependant dominates in T1

IGFII - nutrient dependant dominated in T2 T3

leptin

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11
Q

What is the dominat cell growth mechanism in 0-20 weeks

A

hyperplasia

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12
Q

what is the dominant cell growth mechanims in 20-28 weeks

A

hyperplasia and hypertrophy

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13
Q

what is the dominant cell growth mechnaism in 28-term

A

hypertrophy

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14
Q

where does amniotic flid come from

A

fetal urinary tract
fetal lungs
fetal GI tract

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15
Q

how is bilirubin metablised

A

during gestation clearnance of fetal bilirubin is handled efficiently by the placents

fetus cannot conjugate bilirubin

physiological jaundice is common

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16
Q

where does the ductus arteriosus shunt

A

pulmonary trunk and aorta

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17
Q

why does blood enter the RV

A

due to teh crista dividens to prevent the RV atrophying and allows a small amount of blood to enter the lungs to promote its devlopment

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18
Q

what is symmetrical growth restriction

A

all parts of the foetus are small

19
Q

what is assymetrical growth restriction

A

head sparing

restriction on teh abdomen but is is disproportinatly smaller than the hed

20
Q

how is amniotic fluid recyced

A

inhaling amniotic fluid by fetus practicing breathing movements

swallowing the fluid and so it enters the fetal GI tract. Debris from the GI tract accumulate as meconium which is passed as babys first stool

21
Q

what is the composition of amniotic fluid

A

water, electrolytes and substances and elements of fetal ski

22
Q

what is symphysis findal height

A

a non-invasve way to asses grwoth by measuring the length from the pubic symphysis to yhe top of the fundus

at 20 weeks the SFH should be at the umbilcus

23
Q

what is polyhydramnios

A

a lot of amniotic fluid which can occur due to swallowing difficulties or excessive urine production

24
Q

what is oligohydromanios

A

lack of amniotic fluid

due to IUGR

25
Q

what is the average fetal weight

A

3500g

26
Q

what does a fetal weight of <2500g suggest

A

restrcited growth

27
Q

what does a fetal weight of >4500g

A

macrosomia

28
Q

what cayses low birth weight

A

premature

constituitionaly sma;;

growth restriction

29
Q

how does developemeny of resp systej statrt

A

outpouching of foregut to create the bronchopulmonary tree in the embryonic period

30
Q

what is teh pseudoglandular stage

A

then budding and bracnhing of bronchioles in week 8-16

31
Q

what is fetal viability determied by

A

whether the pneumocytes are present

32
Q

what can you di if preterm delivery is unavoidable

A

give glucoccorticoids to help stimulutae the production of surgacctant in the fetus

33
Q

what is the canalicular stage

A

formation of resp bronchioles in week 16-26

still no alveloi

34
Q

when do alveoli form

A

approximately weeks 26-term

they develop from the ends of resp bronchioles- it is only at this point that type I and II pneumocytes develop

35
Q

what is the corticospinal tract and when does ot form

A

co-ordinated movements require a tract which i the corticospinal tract

4th month

36
Q

when does the mother first feel the baby moving

A

17 weeks

37
Q

what is the aetiology of fetal heart rate acceleratons in utero

A

response to fetal movement

38
Q

what is the normal fetal hr

A

110-160

39
Q

which prenatal diagnostic test has the highest risk of miscariae

A

chorionic villus sampling

40
Q

what is the most common fundal height at 36 weeks

A

xiphersternum

41
Q

what is the most common fundal height at 20 weeks gestation

A

umbilicus

42
Q

what is the most common fundal height at 16 weeks gestation

A

mid-way between pubis and umbilcus

43
Q

what is the most common fundal height at 12 weeks gestation

A

pubic symphysis

44
Q

what is important to give in early pregnancy to promote heathly devlopment of the nervous system

A

folic acid