Parturition and lactation Flashcards
define partuition
the process of giving birth labour
what two anatomical elements are key from partuition and what must happen to them
ripening of cervix and uterine contractions
outline 3 stages of labour briefly
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
what hormone is extremely important in stage 3 of labour delivering the placenta
Oxytocin ensure muscle clamps down on blood vessels to prevent hemorrhage
describe the 3 time frame stages that the cervix undergoes during gestation
quiescent is for 37 weeks, activation cervix starts to ripen and weaken a bit before labour and stimulation the cervix begins to dilate
why does the cervix remain closed for majority of gestation
because a closed cervix is essential to maintaining pregancy
how is the cervix ripened
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
what does cox 2 do
enzyme for prostaglandin production
what enzyme is most important for cervix ripening
metalloproteinases 2 and 9 breaking down the collagen in the cervix
what is functional progesterone hormone withdrawal
actual concentration of progesterone does not decrease it plateaus unlike other mammals and the cells stop being responsive to progesterone
whats causes inflammatory process in cervix
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).
what are the clinical implications of cox 2 being increased at at term
and post partum
pge 2 used to ripen cervix in women who cervix is intact and not ripening
in the quiescent stage of gestation describe uterine contraction activity and why it is favorable to be like this
minimal and this is because the baby is not ready to come out yet and strong frequent contraction for 37 weeks could harm baby
why are there does uterine contractions begin to increase
in preparation for stimulation phase where their will be many strong contractions
describe innervation and vasculrisation of myometrium
lots of vessels good supply, sparsely innervated good due to pain that would be felt potentially
what physiological changes allow preparation of uterus myometrium for labour
contraction associated proteins’ induced: prostaglandin receptor COX-2, oxytocin receptor, gap junctions (connexins), calcium signalling proteins and ion channels Myometrium primed for contraction
for uterine contraction why is up regulation of connexons synthesis so important
so there is a greater conduction of electrical information between smooth muscles cells allowing for a more co-ordinated and strong contraction
what does cervical distension caused by fetal movement do
Cervical distension due to fetal movement and development of uterine contractile activity also triggers
maternal oxytocin release (Fergusson reflex) and local prostaglandin production.
what enzyme is responsible for PGE production
cox2
what hormones and processes cause uterine myometrium contractility to increase
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.
why is oxytocin not that useful in encouraging contractions in premature preganancy
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
pro relaxation occurs for majority of pregnancy, what characterizes this period in smooth muscle cells
calcium in cell is low and extremely negative resting membrane potential not excitable
when are smooth muscle cells in uterus converted from pro relaxation to pro contraction
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
what drug can be used to inhibit uterine contraction and delay labour
nifediprine calium voltage gate inhibitior
during pregancy what happens to resting membrane potential of myometrium
becomes more and more positive from -75 to -45
prior to labour what receptor increases its protein synthesis and why
oxytocin so it is ready to respond
how does ethnicity affect when a child is born
slight variation of timing of birth with white ethnicties taking slightly longer
what is the normal time for a fetus to be born
between 37-41 weeks
why do babies in uk never exceed gestation of more than 42 weeks
medical intervention at this point
why are babies born between 37-41 weeks normally
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
why do pregnancy with multiple children twins triplets tend to give birth earlier
increased amniotic fluid, increased stretch and distension, two placentas
what are the four main theories about what causes regulates timing of labour in humans
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
outline this theory about Fetal HPA, cortisol and PGE2 and its role in pregnancy timing
fetus hpa axis develops and secretes crh, causes acth release which causes cortisol release in mother acting on uterus promoting inflammation and pge 2
when are female breast capable of producing milk
from about 16 weeks of pregnancy but they don’t at this stage
why do females only lactate after pregnancy though the breast have been ready since 16 weeks
inhibited by progesterone and estrogen which decrease in conc after removal of placenta
prolactin hormone conc after pregnancy drops is this normal
yes it was initially high because of inhibition by progesterone and estrogen, but it will rise with suckling
why is suckling so important even with no milk delivery
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.
How does suckling ensure milk production?
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.
How does this milk get to the baby’s mouth
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
