Parturition and lactation

Question 1

define partuition

Answer 1

the process of giving birth labour

Question 2

what two anatomical elements are key from partuition and what must happen to them

Answer 2

ripening of cervix and uterine contractions

Question 3

outline 3 stages of labour briefly

Answer 3

stage 1 - ripening of cervix and developing contraction and dilation of cervix

stage 2- cervix fully dilated strong uterine contraction baby delivered head first

stage 3- extremely strong contractions delivers placenta

Question 4

what hormone is extremely important in stage 3 of labour delivering the placenta

Answer 4

Oxytocin ensure muscle clamps down on blood vessels to prevent hemorrhage

Question 5

describe the 3 time frame stages that the cervix undergoes during gestation

Answer 5

quiescent is for 37 weeks, activation cervix starts to ripen and weaken a bit before labour and stimulation the cervix begins to dilate

Question 6

why does the cervix remain closed for majority of gestation

Answer 6

because a closed cervix is essential to maintaining pregancy

Question 7

how is the cervix ripened

Answer 7

through inflammation, cox 2 enzymes stimulate prostaglandin(PGE 2) production which activates immune response, contributes to metalloproteinases 2 and 9 breaking down collagen in cervix and immune cells and cytokines attacking cervix

Question 8

what does cox 2 do

Answer 8

enzyme for prostaglandin production

Question 9

what enzyme is most important for cervix ripening

Answer 9

metalloproteinases 2 and 9 breaking down the collagen in the cervix

Question 10

what is functional progesterone hormone withdrawal

Answer 10

actual concentration of progesterone does not decrease it plateaus unlike other mammals and the cells stop being responsive to progesterone

Question 11

whats causes inflammatory process in cervix

Answer 11

WHAT INSTIGATES THIS INFLAMMATORY PROCESS?

HORMONE CHANGES - Functional progesterone withdrawal - inflammation and influx of
immune cells, increased corticotrophin releasing hormone and oestrogen,
plus cervical distension → oxytocin → PGR (Ferguson reflex).

Question 12

what are the clinical implications of cox 2 being increased at at term
and post partum

Answer 12

pge 2 used to ripen cervix in women who cervix is intact and not ripening

Question 13

in the quiescent stage of gestation describe uterine contraction activity and why it is favorable to be like this

Answer 13

minimal and this is because the baby is not ready to come out yet and strong frequent contraction for 37 weeks could harm baby

Question 14

why are there does uterine contractions begin to increase

Answer 14

in preparation for stimulation phase where their will be many strong contractions

Question 15

describe innervation and vasculrisation of myometrium

Answer 15

lots of vessels good supply, sparsely innervated good due to pain that would be felt potentially

Question 16

what physiological changes allow preparation of uterus myometrium for labour

Answer 16

contraction associated proteins’
induced: prostaglandin receptor
COX-2, oxytocin receptor,
gap junctions (connexins),
calcium signalling proteins and
ion channels
Myometrium primed for contraction

Question 17

for uterine contraction why is up regulation of connexons synthesis so important

Answer 17

so there is a greater conduction of electrical information between smooth muscles cells allowing for a more co-ordinated and strong contraction

Question 18

what does cervical distension caused by fetal movement do

Answer 18

Cervical distension due to fetal movement and development of uterine contractile activity also triggers
maternal oxytocin release (Fergusson reflex) and local prostaglandin production.

Question 19

what enzyme is responsible for PGE production

Answer 19

cox2

Question 20

what hormones and processes cause uterine myometrium contractility to increase

Answer 20

The initiation of these processes is likely to involve oestrogen, oxytocin, uterine stretch, inflammatory
agents, CRH, and functional progesterone withdrawal. Clinically this information has been translated
into the use of oxytocin as an agent for labour induction and augmentation.

Question 21

why is oxytocin not that useful in encouraging contractions in premature preganancy

Answer 21

because oxytocin receptors are poorly expressed as the stage due to down regulation as you do not want baby to be delivered early in non pathogenic circumstances

Question 22

pro relaxation occurs for majority of pregnancy, what characterizes this period in smooth muscle cells

Answer 22

calcium in cell is low and extremely negative resting membrane potential not excitable

Question 23

when are smooth muscle cells in uterus converted from pro relaxation to pro contraction

Answer 23

Pro-contraction pathways up-regulated in labour - Contraction in smooth muscle involved influx of
calcium through voltage gated ion channels and receptor operated channels involving the release of
inositol trisphosphate (IP3) which amplifies the response by releasing calcium from the SR

Question 24

what drug can be used to inhibit uterine contraction and delay labour

Answer 24

nifediprine calium voltage gate inhibitior

Question 25

during pregancy what happens to resting membrane potential of myometrium

Answer 25

becomes more and more positive from -75 to -45

Question 26

prior to labour what receptor increases its protein synthesis and why

Answer 26

oxytocin so it is ready to respond

Question 27

how does ethnicity affect when a child is born

Answer 27

slight variation of timing of birth with white ethnicties taking slightly longer

Question 28

what is the normal time for a fetus to be born

Answer 28

between 37-41 weeks

Question 29

why do babies in uk never exceed gestation of more than 42 weeks

Answer 29

medical intervention at this point

Question 30

why are babies born between 37-41 weeks normally

Answer 30

because mother cant support growth of baby anymore, ageing placenta , balanced against fetus maturation size and ability to survive in environment makes 37-41 weeks ideal for birth

Question 31

why do pregnancy with multiple children twins triplets tend to give birth earlier

Answer 31

increased amniotic fluid, increased stretch and distension, two placentas

Question 32

what are the four main theories about what causes regulates timing of labour in humans

Answer 32

Several related hypotheses:
1. Placental CRH production is key driver
2. Fetal HPA, cortisol and PGE2
plus a drive for estrogen production (from dehydroepi-androsterone sulphate, DHEAS) plays a key
role,
3. Functional progesterone withdrawal, and
4. Fetal maturation (fetal lung) initiates surfactant
production which stimulates inflammatory response in uterine tissues, this increases cytokine output
and suppresses progesterone transcription events and favours pro-contraction gene regulation

Question 33

outline this theory about Fetal HPA, cortisol and PGE2 and its role in pregnancy timing

Answer 33

fetus hpa axis develops and secretes crh, causes acth release which causes cortisol release in mother acting on uterus promoting inflammation and pge 2

Question 34

when are female breast capable of producing milk

Answer 34

from about 16 weeks of pregnancy but they don’t at this stage

Question 35

why do females only lactate after pregnancy though the breast have been ready since 16 weeks

Answer 35

inhibited by progesterone and estrogen which decrease in conc after removal of placenta

Question 36

prolactin hormone conc after pregnancy drops is this normal

Answer 36

yes it was initially high because of inhibition by progesterone and estrogen, but it will rise with suckling

Question 37

why is suckling so important even with no milk delivery

Answer 37

Prolactin concentrations also
drop, but there is a steady maintained plateau after pregnancy as long as there is suckling. Without
suckling, prolactin remains at lower levels for a few weeks - milk production, but scant. Suckling
ensures that prolactin production is maintained and that full lactogeneisis can occur.

Question 38

How does suckling ensure milk production?

Answer 38

Neuroendocrine reflex, suckling induces an impulse via the spinal cord and brain stem to stimulate
vasoactive intestinal peptide (VIP) production from the paraventricular nucleus in the hypothalamus.
This induces prolactin synthesis in the anterior pituitary and release into the maternal circulation.
Suckling also suppresses dopamine production (dopamine inhibits prolactin production) therefore
increasing prolactin release. The strength and duration of suckling will determine the subsequent level
of prolactin production.

Question 39

How does this milk get to the baby’s mouth

Answer 39

Suckling again
stimulates this milk ejection reflex. Suckling signals via the spinal cord and brain stem to the
hypothalamus. Suckling stimulates the supraoptic and paraventricular neurones to produce oxytocin
production and stimulate oxytocin release into the maternal circulation. The oxytocin stimulated the
myoepithelial cells that surround the alveoli lobules storing the milk. The cells contract, pushing milk
into the ducts and increasing intra-mammary pressure (let down reflex) enabling the suckling infant
to draw the milk out through the nipple