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RDA > Pregnancy/Labour > Flashcards

Pregnancy/Labour Flashcards

1
Q

How many trimesters are there in pregnancy?

A

3- 1st till 16 weeks, 2nd 17-26 and 3rd 27-40

There is a greater risk of miscarriage in the first trimester due to teratogens after this is complete it is likely that the pregnancy will continue to full term.

Survival outside the womb is 27 weeks and before 37 weeks is premature after 41 is post-term.

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2
Q

What are the maternal changes during pregnancy?

A

increased weight -3rd (10-15 Kg)
increased blood volume - 2nd and later
increased blood clotting tendency - 2nd and later
decreased blood pressure - 2nd (if she stands up she is more likely to fall over - postural hypotension)
altered brain function - 1st and later
altered hormones - 1st and later
altered appetite (quantity and quality- cravings refelct what the baby is lacking)- 1st and later
altered fluid balance -2nd and later ( may be linked to the lower bp)
altered emotional state - 1st and later (can be elated or low mood)
altered joints - 3rd
altered immune system - 1st and later

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3
Q

What are the hormonal changes in pregnancy?

A

Hcg is a functional homologue of LH which drives the production of oestrogen and progesterone from ovaries to drive the formation of the corpus luteum.

The corpus luteum is driven to keep producing progestrone to maintain the endometrium by hcg.

placental lactogen increases as the size of the placenta changes.

Hcg is high in the first trimester but decreases after as the oestrogen and the progesterone increase. PROGESTERONE IS VITAL.

at about week 10 the placenta will take over the formation of progesterone.

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4
Q

what does the fertlised egg look like?

A

two pronuclei joining their chromosomes but no nuclear membrane.

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5
Q

What is conceptus?

A

everything resulting from the fertilised egg.

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6
Q

What is an embryo?

A

the baby before it is clearly human (i.e. before 8 weeks)

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7
Q

What is a fetus?

A

the baby for the rest of the pregnancy.

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8
Q

What is an infant?

A

The baby after is has been born

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9
Q

What happens during development?

A

starts off as a bilayer of two cells - epiblast and hypoblast. (blastocyst)

Embryo- there is a head and eye + liver formed. limbs begin to form (5-6 weeks)

Fetus - (3 months) –> human as primary structures are all there. Arms, legs, head, eyes, liver, toes etc..

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10
Q

What is the timing issues in pregnancy?

A

It is counted from the first day after the final menstrual period.

Cannot use day of ovulation as we do not know exactly when this is.

Discrepency of two weeks but this does not greatly affect the term dates.

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11
Q

What is the job of the placenta?

A

Separation of blood supplies of mother and baby

  • Exchange of nutrients (maternal to foetal) and waste products (foetal to maternal)
  • Connection (or anchorage)
  • Immunoregulation – allows the maternal immune system to switch off, allowing for pregnancy
  • Biosynthesis (e.g. progesterone, oestrogens and hCG)
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12
Q

Describe the primary structure of the placenta?

A

The primary subunit is the placental villi - this is extremley branched - provides a large surface for the exchange of nutrients between the foetus and mother - placental villus also anchors the placenta.

Within each villus there is a complex blood supply, including arterial and venous vessels, connected to smaller capillaries in the terminal portions of each villus. The fetus and mothers blood supply are in close proximity but do not mix.

NB the placenta parallels the lungs as the veins carry oxygenated blood and arteries de-oxygenated.

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13
Q

How do placentas develop?

A

At day 9 the conceptus is almost fully implanted into the endometrium and their outer layers are multinucleate syncytiotrophoblast which contains fluid filled lanucae.

the underlying layer of cytotrophoblasts are proliferating adjacent to the embryo and this is where the placenta will develop from.

from implantation the cytotrophoblast will proliferate into synctium and this will then form a cytotrophoblast column. This then undergoes branching (villius sprouting). the mesenchymal cells lining the inside will become the villius vasculature and branching will continue.

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14
Q

Describe what happens with cytotrophoblasts?

A

These limit the amount of oxygen to the embryo during early development by forming a shell around the embryo.

The baby is growing rapidly and it is thought that the limited blood supply is avoiding the oxygen free radicals from forming and harming the foetus.

the spinal arteries are remodelled in the 2nd and third trimester when an infant growth is greatest - these have an important role in the delivery pathology.

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15
Q

Describe the stages of pregnancy?

A

At the earliest stages of pregnancy, the conceptus is in contact with maternal endometrial cells

  • As it grows, it makes transient contact with the maternal capillaries
  • But the rapidly proliferating cytotrophoblast cells form a shell around the conceptus
  • This isolates it from maternal blood by about 4 weeks post fertilisation.
  • The decidual glands hypertrophy during the first trimester of human pregnancy
  • These provide the nutrients for the placenta and developing baby
  • The source of the nutrients (glands: histotrophic) rather than maternal blood (haemotrophic) is different
  • The cytotrophoblast shell remains in place until about 8 weeks post-fertilisation (10 weeks GA)
  • Cytotrophoblast plugs block the spiral arteries –> these are broken down and this allows maternal blood through spiral arteries. this leads to an increase pressure on the placenta –> this is the point in which the placenta must be anchored properly or there will be loss of the foetus.
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16
Q

What is miscarriage?

A

loss of a viable preganancy - usually within 13 weeks.

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17
Q

When is delivery usually at?

A

37-41 weeks

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18
Q

When is a delivery considered preterm?

A

23-37 weeks

unlikely to survive before 22 weeks

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19
Q

How does labour begin?

A

It starts as organised contractions from the fundus to the base.

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20
Q

What is the process of labour?

A

Cervical ripening and effacement (increasing)

  • Co-ordinated myometrial contractions (increasing)
  • Rupture of fetal membranes
  • Delivery of infant
  • Delivery of placenta
  • Contraction of uterus
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21
Q

What is braxton-hicks contractions?

A

partial contractions

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22
Q

What are the phases of labour?

A

PHASE I: can last many hours, and involves contractions and cervical/uterine changes

o Contractions become more powerful and more coordinated

o The cervix begins to soften (ripening) and gets thinner (effacement)

o The length of phase I is incredibly variable (12 to 48 hours)

  • PHASE II: can last hours, and the baby is delivered in this phase
  • PHASE III: approximately half an hour long, in which the placenta is delivered

LONGEST IN THE FIRST PREGNANCY SHE HAS.

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23
Q

What is happening in cervical ripening and effacement?

A

inflammatory process in the cervix

with remodelling of ecm

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24
Q

What is happening in the myometrial contractions?

A

Prostaglandins are very importnat in this process.

Increased oxytocin receptors.

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25
Q

What happens in the rupture fetal membranes?

A

inflammatory process - leukocyte recruitment.

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26
Q

What is the key TF?

A

NF-KB- many initiators and they drive the process in labour seen below.

COX-2 controls prostaglandin productions and MMP Which are important in the inflammatory regulation.
IL-8,IL-B (can further drive the NFKB), oxytocin receptor, PG receptors, contraction-associated proteins.

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27
Q

What does PGE2 lead to?

A

There is an increase in prostaglandins.

28
Q

What are the two key drivers of normal term labour?

A

PAF (platelet activating factors is also part of the lung surfactant - this increase in its levels very quickly in the weeks beore pregnancy as this means that they baby can breathe air)

CRH increases in the three weeks before delivery every quickly. Can be driven up by stress and multiple preganancies.

Infection can drive preterm labour - use entoxin to miminc this.

29
Q

What is the hypothesis of partuition?

A

The high levels of CRH will start to switch UP IL and prostaglandin production in the foetal membranes

o Cortisol from the adrenal gland is acting on the foetal lung

o It stimulates the foetal lungs to produce surfactant (including PAF)

o Therefore, high levels of cortisol production à more surfactant produced (MORE PAF PRODUCED)

o Lungs are in intimate contact with amniotic fluid (baby takes amniotic fluid into lungs, and expels it)

o This allows PAF to enter the amniotic fluid, and PAF upregulates the same factors in the membranes

o PAF is a signal that the lungs are mature, and therefore the baby is safe to be born

30
Q

What is vital in pregnancy?

A

progestereone - will remain high until after the delivery of the placenta

During pregnancy there is a lot of progesterone receptors which can bind to NFKB which can stop the pro-inflammatory effects.

At the end of preganancy the progestrone receptor levels go down and NFKB go up. There is still a high progesterone but there are no receptors to bind to so the NFKB effects pre-dominate.

31
Q

What produces progesterone during pregnancy?

A

the corpus luteum is the main source but you also get the production of progesterone by the placenta.

At 9 weeks the corpus lueteum will stop producing progesterone and this will rely on the placenta which will increase the levels this is the luteo-placental shift.

32
Q

Describe the production of oestrogens once the corpus luteum has stopped producing them:

A

this then shifts also to the placenta however it does not have the enzymes that are needed to convert the pregnelenone into the sex steroid.

This therfore will need to use the fetal adrenals to form the weak DHEA. This is then sulphates and this inacctivates it so that the foetus is not exposed to the androgen.

This is then converted into 17-B oestradiol.

33
Q

How is oestriol (which is very high in preganancy formed):

A

This is through a similar mechanism to the oestradiol.

The DHEA-S is hydroxylates to give 16-OH DHEA-S and this is the precursor.

This shows that the mother, fetus, placenta are all interconnected.

34
Q

Why does the blood increase its clotting ability the start of pregnancy?

A

to reduce the blood loss during delivery.

35
Q

Why should pregnant women not stand for too long?

A

this is due to their lower blood pressure that puts them at risk of fainting.

This will increase in the thrid trimester.

36
Q

Why does body temp increase during pregnancy:

A

this is to do with the high levels of progesterone which maintain a high temp.

As the fetus grows it will also contribute to the mothers temperature.

37
Q

What is the increase in breast size dependant on:

A

the hormones that are present and their levels:

  • prolactin
  • oestrogens
  • human placental lactogen
38
Q

what is hyperemesis gravidarum?

A

the most severe form of morning sickness.

this is highest in the first trimester and is thought to be due to the high levels of hcg.

39
Q

Why is there altered brain function?

A

due to the high hormone levels espescially progesterone.

There is also a slight decrease in brain size but this is not functional.

40
Q

Why is appetite altered during pregnancy?

A

this is due to the increasing size of the fetus impacting the gastr-intestinal system which decreases the distensibility of the stomach and so the mother may have to have 6 smaller meals a day rather than 3 big ones.

41
Q

Why is there alterated urine frequency during pregnancy?

A

this will increase in the first trimester as there is a change in hormones which will increase the fluid retension and increase the plasma volume.

This normalises in the second and in the third it will increase again.

this is because the uterus is greatly increased in size and this leads to a greater pressure on the bladder. This means that there will be more frequent smaller urine volumes.

42
Q

Why are there altered emotions during pregnancy?

A

This is due to the levels of the horomones which mean that the mother can be elated or feeling low.

43
Q

Why are there changes to the joint structure during pregnancy?

A

the pelvic girdle will alter to make connections that make it more flexible this will be permenant after the fetus is born.

44
Q

How and why is there altered immune system during pregnancy?

A

This is so the foetus is not recognised as non-self and attacked by the immune system.

The placenta produced HLA-G which invariant compared to normal HLA. This HLA-G is used to inform the immune system that the fetus is human and so it will not attack it as it is not non-self. - acts as a human marker

At the uetero-placental junction there is supression of the immune system and an increase in Th2 but a decrease in Th1

45
Q

What is the only condition in which it is viable to live with a chromsome missing?

A

Turner’s syndrome - X0

46
Q

What are the risks associated with a preterm baby?

A

Tertatogens can lead to complications such as cleft lip/palate and spina bifida.

the lungs, digestive system, immune system and brain are all developed late. most preterm pregnancies are due to a uterine infection –> the baby’s brain is very vulnerable to inflammatory mediators and this can lead to brain damage.

47
Q

What is embryology?

A

the process in which a single cells develops into a recognisable human being - this is usually over 8 weeks.

48
Q

How does the timings of embryo development vary to preganancy?

A

in embryo development it is counted from the point of fertilisation where pregnancy is counted from the first day of the last period.

post-fertilisation is 2 weeks after the GA

49
Q

What are the subunits within the placenta?

A

cotyledons - each contains one or more villi

50
Q

how does the foetal contact with the mother change during pregnancy?

A

at first the foetus is in contact with the mother endometrial cells.

As it grows it is in contact with the maternal capillaries

at about 4 weeks the conceptus will surround the fetus and separate it from the mother’s blood.

51
Q

describe how the nutrient supply changes during pregnancy:

A

the decidua will hypertrophy to provide the nutrients for the fetus in the first trimester.

At around 8 weeks post fertilisaion a cytotrophblast plug forms blocking the spiral arteries.

This will break down at around 10-12 weeks gestaional to provide the fetus with nutrients via the spiral arteries.

52
Q

Why is the transfer from placental suppply to the maternal blood supply for nutrients dangerous?

A

if the placenta is not anchored properly this will lead to the risk of miscarriage as there is an increase in pressure meaning that the placenta can detach from the mother.

53
Q

describe the changes go the spiral arteries and why?

A

the vascular endothelium and the smooth muscle are lost - this is to increase the blood flow to the fetus.

the loss of the smooth muscle means that it does not respond to vasoconstrictors.

no nervous system = no pain

54
Q

what are maternal risks during labour?

A

remodelling of the spiral arteries means there cannot be any action of the vasoconstriction.

Involution of the uterus is needed to block the spiral arteries and stop blood loss.

55
Q

what are the risks to the infant during preganancy?

A

Partial chromosome loss, exchange of sequences between chromosomes, chimeras and mosaics

i.e. changes in chromosomes number.

56
Q

what are the stages of labour?

A

first stage - uterine contractions to the os uteri dilation. –> this is the longest stage and begins with the rupture of the fetal membranes including the amniotic sac (hence water breaking).

second stage - expulsive stage beginning with dilation of the cervix to expulsion of the infant. (this usually is 30 mins long)

third stage - completed with the expulsion of the placenta and the membrane. (THERE MUST BE REMOVAL OF THE PLACENTA AS IT IS INFLEXIBLE (STOPS UTERINE CONTRACTIONS) + INVOLUTION OF THE UTERUS TO BLOCK THE SPIRAL ARTERIES AND REDUCE BLOOD LOSS.)

57
Q

why is the involution of the uterus following the delivery of the placenta important?

A

this is how blood from the spiral arteries stops flowing through.

this leads to an increase in oxytocin.

58
Q

What is cervical effacement?

A

ripening - softer + flexible

dilation - thinner and stretched sideways.

59
Q

what is labour defined by?

A

fundally dominant contractions.

the contractions are in an organised manner from fundus to base and this is used to push the fetus out.

60
Q

what are braxton-hicks contractions?

A

this is in the 8 weeks before delivery.

not just relaxed briefly contracts then relaxes again. This happens intermittently.

61
Q

what are the main events during labour and what controls these events?

A
  1. cervical effacement and ripening (cervix becomes softer and thinner. this requires remodelling/loss of the ecm. involves IL-8, PGE2, MMP. increasing pressure of the head on the cervix will increase the strength of teh contractions + decrease the time between them)
  2. co-ordinated myometrial contractions –> from the fundus down to push the infant out. (high PGE2 and an increase in oxytocin receptors)
  3. delivery of the infant
  4. delivery of the placenta
  5. contraction of uterus to prevent maternal blood loss.
62
Q

what key TF is associated with labour and what can up-regulate this?

A

NFKB is associated with all the genes that are pro-labour.

it is increased by IL-1B.

63
Q

what foetal factors act to control labour?

A

as the foetus matures there will be an increase in surfactant - this releases PAF.

there will also be an increase in CRH.

these will both increase the levels of PGE2, COX-2 (needed to form PG) and IL-1B (increases NFKB)

64
Q

what factors can lead to a preterm delivery?

A

anything that increases the stress on the mother as this will increase the levels of CRH (e.g. multiple pregnancies)

anything that increases the levels of inflammatory mediators (such as uterine infection)

anything that increases muscle contraction (such as multiple pregnancies pushing on the cervix.)

65
Q

what happens to progesterone during labour?

A

lower levels of progesterone initiate labour BUT the levels will still be high.

this is mediated by PG-B and not A.

RDA (7 decks)

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