Week 4- Week 4: The placenta and membranes Flashcards
List 4 unique and amazing facts about the placenta
- only temporary organ
- only organ shared between two people
- only lasts for as long as it s needed
- expelled without leaving a scar
- a healthy placenta almost always means a healthy baby
Explain the significance of the placenta in other cultures
Western= often thought of as gross or a taboo topic.
Maori and some Aboriginal peoples= sacred and will bury placenta often under a tree to ground the child to the earth. This spiritually links the child to country.
Chinese culture= it is traditionally dryied and used in traditional Chinese medicines as it is though to prevent/manage post natal depression as it is still rich in pregnancy hormones and nutrients.
Briefly explain the development of the placenta and when it is functional.
Placenta may commence development early when the trophoblast embeds in the endometrium and continues to develop through the embryonic period. However, it is not fully functional until the beginning of the second trimester, as the corpus luteum degenerates.
List 4 functions of the placenta
Respiratory: O2 and Co2 gas exchange between woman and fetus
Nutritive: baby receives nutrients though placenta
Excretory: baby removes waste products through placenta
Hormonal: some pregnancy specific hormes are produced by the placenta e.g. HCG, HPL, Relaxin, Oestrogen and progesterone
What is the process of development and formation of the placenta called
Placentation
What kind of tissue is a placenta attracted to and more likely to attach to?
Scar tissue from a previous pregnancy
Where is the most ideal place for a placenta to grow?
posterior wall of uterus (well away from the cervix os)
anterior placenta is still safe and normal, howeverrm can be more difficult for mother to feel fetal movements as the placenta reduces sensation and impact of movements.
Outline the development of the placenta
begins at implantation
- blastocyst adheres to the endothelium
- trophobast cells differentiate into an outer cytotrophoblast layer and an inner syncytiotrophoblast layer.
- as the cytotrophoblast proliferates, newly formed cells migrate into the syncytiotrophoblast and lose their cell membranes. This forms a rapidly growing mass.
- cytotrophoblast secretes proteolytic enzymes
- syncytiotrophoblast secretes sends out finger like projections allowing blastocyst to ashere to the endometrum.
- Lacunae or spaces begin to form within syncytiotrophoblast.
- syncytiotrophoblast errodes endometrial blood vessels and glands, lacunse become filled with maternal blood and glandular secretions
- lacunae fuse to form a network of which maternal blood flows
- by the end of week 2, small projections fo the cytotrophoblast begin to protrude into the syncytiotrophoblast forming primary chronic villi
- early in the second week extraembryonic mesoderm grows into these villi forming a core of loose connective tissue. (known as secondary chronic villi)
- by the end of the third week, embryonic blood vessels have begun to form in the extra embryonic mesoderm of secondary chronic villi transforming into tertiary chronic vili
- cytotrophoblast cells from the tertiary villis grow towards the decidua bisallis and spread across it to form a cytotrophoblast shell
- villis that are connected to the decidua basalis though the side of the trophoblastic cell are called anchoring villus
- villi growing from the sides of stem billi are called branch villis
- branch villis are surrounded by intra villi space= serves as the main site of exchange between mother and fetus
- by the 4th week fetal blood flow is established.
- 2 A and 1V divide into capillaries in the branch villi and exchange across placental membrane
By what week of pregnancy is fetal blood flow established?
4th week
How may artier and veins does an umbilical cord have and which are oxygenated?
2 arteries (deoxygenated) 1 vein (oxygenated)
Placenta previa
When the placenta grows over the OS. Makes vaginal birth impossible
An indication for a caesarean.
Name the three component of the placenta and whether they are maternal or fetal.
- Basal plate (maternal)
- Pool of blood (shared)
- Chronic plate + trophoblast projections (fetal)
What is the decidua basalis?
a layer of the basal plate
Roles:
- regulate syncytiotrophoblast invasion
- provide nutrition and gas exchange
- produce hormones
What is the chorioamnion membrane composed of?
Fromed by the basal and chrnoic plate coming together and meeting at the edge of the placenta.
Composed of two membranes:
- amnion (fetal)
- Chorion (maternal)
Describe the amnion, its function and any complications associated with it.
- The inner membrane (fetal)
- derived from inner cell mass and consists of epithelium with a connective tissue base.
- tough, smooth and transculent membrane
- continuous with the outer surface of the umbilical cord
- moves over the chorion aided by muscus
Function
- contain amniotic fluid
- produce small amounts of amniotic fluid
- produce prostaglandin E2 (aid in induction of labour)
Complications
- In rare instances, the amnion can peel away from the sack in early pregnancy and wrap around the limbs of the fetus, causing amniotic bands that can affect the growth of that limb.
Describe the Chorion, its composition, its function and any complications associated with it.
- Outer membrane (maternal)
- continuous with the placenta
- fragile and can easily rupture
Composed of;
- mesenchyme
- cytotrophoblasts
- vessels form the extended spiral arteries of the decidua basalis (this is the membrane closest to the woman’s uterus - the maternal surface)
- rough, fibrous, opaque
- loosely attached
Function
- produces enzymes that can reduce progesterone levels (help to induce labour)
- produces prostaglandins, oxytocin and platelet-activating factor which stimulate uterine activity
Complications
- friable and can rupture easily, which makes it relatively easy to be retained in the uterus following birth (usually coming away on its own within days after birth, other times requiring surgical removal).
Describe amniotic fluid and how it is produces.
- clear, the alkaline liquid contained within the amniotic sac.
Produces
- derived form maternal circulation across the placental membranes and exuded from fetal surface.
- from the waste of fetal metabolism e.g. urine and lung fluid
List some function of amniotic fluid
- distended the amniotic sac to allow for growth and free movement of the fetus= this assists with symmetrical MSK development
- equalised pressure
- protects fetus from injury
- maintains constant intrauterine temp (protects fetus from health loss)
provides small amount of nutrients - in labour, as long as the membranes remain intact the amniotic fluid protects the placenta and umbilical cord from the pressure of uterine contractions, and assists in facilitating the rotation of the fetus into the pelvis
- aids effacement (shortening and thinning) of the cervix and dilation of the internal cervical os (internal opening of the cervix to the uterus), particularly where the presenting part is poorly applied.
What composes amniotic fluid, volume + colours.
Amniotic fluid
- 99% water
- 1% being dissolved solid matter including food substances and waste products.
- During pregnancy, amniotic fluid increases in volume as the fetus grows: from 20 ml at 10 weeks to approximately 500 mls at term.
+ the fetus sheds skin cells, vernix caseosa and lanugo into the fluid.
- Normal amniotic fluid is clear/pink or even slightly straw coloured.
- Green or yellow amniotic fluid can indicate that the fetus has opened its bowels in-utero (this is called meconium-stained liquor - MSL), and this may be a cause for concern.
- Bright red or brown amniotic fluid can indicate intrauterine bleeding, possibly from the placenta or the fetus, and is usually an emergency.
Define the first stage of labour + name the phases.
The onset of painful, regular contractions resulting in effacement and dilation of the cervix.
from nil/0 to fully dilated (10cm )
- can take up to 16hrs in first time mother
- up to 10 hours for a multi
- Think LAT
1. Latent
2. Active
3. Transitional - All women need thorough education during pregnancy
that labour and birth are a normal process - Encouraging women to listen and trust her body,
surrounding herself with supportive people and
remembering there are variations in ‘normal’ will help her
labour progress
Explain each phase of the first stage of labour
Latent
- from very first contraction to cervix is 4cm
- 0-4cm dilation
- Cervix effaces – shortens from 3cm to 0.5cm long
- contractions= mild strength, infrequent
- slow dilation
- some may not experience this phase
- uncomfortable, cant sleep
- 1st baby 12hrs
- 2nd + 6-8 hrs
- effacement= fundance gets bigger and stronger and pulls upwards
- best for woman to be at home in this stage for relaxing.
- don’t diagnose active phase when in lateant as unnecessary intervention may occur.
Active
- from 4cm to fully dilated/8cm (usually not always- you can be latent at 4 cm!)
(approx 0.5-1.5cm per hour BUT EVEYONE IS DIFFERENT)
someone might dilate faster one hour and not at all in one hour.
- 4cm to 8cm
- more rapid dilation of cervix
- contractions= more frequent, coordinated, stronger and progressive descent of presenting part into pelvis.
RHYTHMIC
- 4 contractions in 10 mins that last 1 min long.
Transitional - just prior to second stage, - happens along with active labour - from 8cm - 10cm (fully dilated) - Crisis of confidence - characterised by woman feeling distressed, exhausted, like she is getting nowhere, and her mood, noises and responses might be completely out of character. (A LOT of women will say "I can't do this anymore!" or "I just want to go home!" in transition). - not all women experience this phase
Define the second stage of labour and name its phases
Period form end of first stage (fully dilated) until birth of baby.
Lull
- After full dilation of cervix
10-30-60 mins
- the restful stage, women energy renews before baby is pushed out
- sometimes confused with labour stoping (some practitioners may try augmentation of labour ARP or oxytocin/syntocinon)
- Cervix may be fully dilated but the presenting part may have not yet reached the pelvic outlet.
- Woman may not feel expulsive urge until the presenting part (PP) has descended further
- Woman may ‘go into self’ or even sleep.
Expulsive/descent phase
- contractions shorten uterine cavity this forces the baby into the pelvis and women pushing efforts propel presenting part into the pelvis.
- The descent of the baby into the pelvis on to the pelvic floor triggers Ferguson’s reflex
- The woman may have an ‘uncontrollable’ urge to push or bearing down feeling
- Changes in vocalisation – ‘grunting’
- Urge to defecate or may defecate (completely normal, and actually can be beneficial to the baby, more on that later in the course).
- Pouting anus
- Perineum bulges
- Visible presenting part, retracts between contractions.
Define the third stage of labour
- the separation of the placenta from the uterine wall
- expulsion of the placenta and membranes from the uterus and vagina
- control of bleeding.
What role do contractions play after the birth of the baby? and how
Contractions occlude the bleeding vessels that have supplied placenta= controlling bleeding.
How are contractions initiated if the positive feedback system after labour is completed and baby is born?
- The emotions after birth trigger the release of oxytocin (love hormone) which stimulates contractions of the uterus.
- if baby suckles on breast oxytocin release is much greater.
Oxytocin can be injected to maintain contraction. This is active management of the third stage
What the term given when intervention is provided via injection of hormones and cord traction in the third stage.
Active management of the third stage of labour.
This is the opposite of physiological management which is free of intervention.
Describe the fourth stage of labour and what occurs in it.
- first hour (or the “Golden Hour”) after birth for both mother and baby.
- monitoring
- preventing maternal bleeding
- baby observations to ensure normal adaption to extrauterine life.
What 9 stages will a new born move through in the first hours of life if left un disturbed and having skin on skin?
In this hour, if left undisturbed and skin-to-skin on mother’s chest, a baby should
spontaneously move through the following 9 stages.
1) The Birth Cry
2) Relaxation
3) Awakening
4) Activity
5) Resting
6) Crawling
7) Familiarisation
8) Suckling
9) Sleeping
Define labour and what are the mechanics of it?
Regular and coordinated muscular contractions of the uterus.
The fundus hardens and tightens and pull the uterus up which effaces and dilates the cervix.
- this results in repulsive contraction and birth of baby + placenta
What are the 4 key events of labour?
- regular, strong, coordinated contractions (effective)
- effacement and dilation of the cervix
- Birth of the baby
- Birth of the placenta
List and explain some uterine changes that occur in preparation for labour.
- Myometrial cells= are capable of activity without external stimulation (we don’t fully understand this)
- Uterotonic inhibitors (e.g. progesterone) decrease. During pregnancy, these uterotonic inhibitors prevent contraction, however as they diminish contractions gradually increase in intensity, frequency, strength, synchronicity and lead to effective labour
- myometrial cells change the structure (activation) so they can contract more strongly + continue throughout labour
- electrical activity increases
- ratio of hormones changes
- Myometrial cells become more responsive
- Increase in number of ion channels (think back to muscle contraction and how increased Ca for example could be extremely helpful and increase strength of contraction)
In the last few weeks of pregnancy, uterotonic inhibitors
decrease, while oestrogen and contraction-associated
proteins (CAPs) increase
▪ More responsive to electrical activity and increased
responsiveness of target tissues
Explain how the cervix stretches if it has not stretched the whole pregnancy?
- High content of connective tissue (made up of collagen fibres) resists stretching during pregnancy
- Stretching of the cervix results in local release of prostaglandin F2alpha and the release of oxytocin from the posterior pituitary gland- which increases uterine activity = labour begins
Describe ripening
Ripening= a softening process characterised by infiltration of leucocytes, increase in water, decrease in collagen content
- separate to contractions meaning we don’t need contractions for the cervix to ripen
the process of ripening begins well before labour
What are the 5 main processes that initiate and play a role in labour
- Corticotrophin-releasing hormone (CRH)
- Prostaglandins (PGE2 & PGF2alpha)
- Oxytocin
- Oestrogen
- Progesterone
What is the role Corticotrophin-releasing hormone (CRH)
Under the influence of oxytocin during labour it binds to different receptor types and promotes uterine contractions (enhances contractility)
What is the role of Prostaglandins (PGE2 & PGF2alpha)
Stimulate smooth muscle fibres to contract, formation of gap junctions (help to get rid of uterotonic inhibitors), increase calcium levels in myometrial cells (As well as
softening the cervix)
What is the role and release of oxytocin
Released in response to tactile stimulation of the reproductive tract (ripening cervix).
e. g. baby head pushes on cervix= contractions increase
- Increase of oxytocin receptors in decidua is 300 fold by term.
- Oxytocin binds to these receptors, stimulates the release of prostaglandins and stimulates uterine pacemakers.
- oxytocin is the love and labour hormone
What is the role of Oestrogen
Increases sensitivity of myometrial oxytocin receptors (facilitates myometrial contractility)
What is the role of Progesterone
During pregnancy, progesterone suppresses uterine excitement.
Before labour, the availability of progesterone decreases, and oestrogen synthesis increases resulting in an increased oestrogen/progesterone ratio that allows the uterotonic effect of oestrogen to dominate
What key events has to occur for labour to begin
Prior to labour, change in oestrogen/progesterone ratio
allows for activation of uterine muscle and ripening of
cervix
Why is it so important for a midwife to understand oxytocin?
Oxytocin is what relaxes the body and brings on contractions through a positive feedback loop.
For effective labour, we need to encourage the production of oxytocin by
- creating a safe space
- using soft language
- promoting physical contact and love
- promote trust
WHO definition of normal labour
Spontaneous onset between 37-42 completed weeks of pregnancy
– Low risk at the start and remaining throughout until birth
– Spontaneous birth of baby in vertex position
– Mother and baby in good condition after birth
Define effacement
Fundance gets bigger and stronger and pulls upwards
List some of the idea managements of labour
- remain at home in their space for as long as possible (+ explain why this is. Oxytocin will be released when you are calm and in your known space) Adrenaline is produced when scared to in a new space which will stop oxctocin
- ensure appropriate support
- encourage women to remain at home
- may be assessed in-home/hospital- VE/FH
- Sleep if possible
- continue to eat and drink
- Strategies for pain management (these keep gravity helping descent)
* Walk
* Warm bath/shower
* Continue normal activities
Why should you avoid paracetamol in the first stage of labour?
Paracetamol is a prostaglandin inhibitor
What are the two types of labour?
True labour
Spurious
Describe True labour
- causes effacement and dilation
- contractions are effective, regular, increasing in frequency and intensity
characterised by discomfort in the lower back radiating to the abdomen - pain is not relieved by ambulation
- head descends
Describe spurious labour
- contractions don’t change cervix
- not just not change in a few hours. Its ‘ been 24hrs with no changes and we thought this was a long latent phase so maybe this is spurious labour’
- tightness not pain (stomach and groin)
to assist
- position of baby? work to chnage this if bad
- massage and relax women to encourage oxytocin and therefore true contractions
What are some support factors that can affect labour process?
- trust woman’s body and the birthing process (creates oxytocin)
- sensitive, encouraging and appropriate support people
- comfortable environment
- known, trusted caregiver (require less pain management and progress though labour faster)
- opportunity for rest, and ability to eat and drink as the woman wants
- sitting on a toilet= private, pelvic floor relaxes
When should a women call and come into hospital?
- Ruptured membranes
- Regular, painful contractions that she is not managing/needs advice about
- Vaginal bleeding (as opposed to a ‘show)
- Any continuous pain
- Reduced fetal movements OR change in fetal movements from normal
- If she is concerned (about anything)
When should be assessed?
- Regular, strong, painful contractions she wants to come in
– Ruptured membranes (may be able to go home again if not mec- green, yellow fluid)
– Bleeding
– Decreased fetal movements
What is an Iatrogenic complication
illness or complication created by a medical practitioner
What is the midwifes role in the first stage of labour?
- Assess well-being woman and baby (mental health pf mother, fetal heart rate from start of contraction until 1 min after contraction)
- Support woman and partner – reassurance
- Keep informed (let them know the assessment findings)
- Assess progress (abdominal palpations, FHR)
- Ensure appropriate nutrition & fluids
- Provide coping strategies- positioning/mobile/heat/water
- ‘Being there’ what do they need?
- Escalate and manage with collaborative team when things deviate from normal
List some assessments carried out during active labour
Vital signs ▪ Fetal heart rate ▪ Contractions ▪ Abdominal palpation ▪ Vaginal examination ▪ Vaginal loss ▪ Fluid balance ▪ Coping / pain
Pulse for 30mins (Along with FH to ensure they are different and that we haven’t listening to baby)
BP 2hrly
Temp 4hrly
FHR 30mins 1st stage (more in second)
Abdominal palp 4rly (woman needs to lye on their back and this can be uncomfortable so they can decline)
VE 4hrs when in established labour
What is the normal range of fetal heart rate
120-160 bpm
Tacycardia >160 (may need CTG)
Bradycardia <110 (may need CTG)
Emergency type of fetal tachycardia is characterised by
A drop in FHR below 100bpm for >5mins (emergency situation)
Deceleration= dropping below baseline >15bpm then returning
▪ potential problem need full CTG
During the second stage of labour (lull + explosive) how frequently do we check fetal HR?
Every 5 mins (after each contraction)
What is a CTG
Fetal ECG
Describe the mechanics of a contractions
The fundus (top thick muscle) retracts/ contractions (shortens) - retracts after this
- pushes fetus down
contracts are rhythmic and regular which assists in pushing the baby down.
How to assess if contractions have changes
Number of contractions in a minute.
- assess regularity and strength
- from the beginning on one to the next one
e.g. Measurement of contractions (hold hand on fundus for 10 minutes)
2 in 10 mins
mild/moderate/strong
30 sec/ 40 sec/ 55+ sec
What are the main goals of fluid balance in labour?
- maintain fluids (prevent dehydration)
- light diet (prevent ketosis/maintain energy)
- empty bladder (provides room in pelvis + reduces the likelihood of damage to bladder and urethra at birth) sitting on toilet relaxes pelvic floor
- vomit (maybe a sign of progressing labour)
Why is it important for a women to empty her bladder during labour and post birth?
- provides room in pelvis
- reduces likelihood of damage to bladder and urethra at birth
Post birth
- it may shift the uterus to one side and therefore prevent it from correctly contracting and make it hard to palpate/assess thus making it hard to recognise complications.
Outline he causes of pain in pregnancy
- contractions
- dilation of the cervix
- stretching of the vagina + perineum
- pressure of baby on pelvic floor
Describe is the pathway of pain in relation to labour
- site experiences pain
First neuron - impulse travels along asending sensory tract
- impulse arrives at dorsal root ganglion of posterior horn
Second neuron
- from psterior horn, impulse crosses spinal cord
- impulse travels to medulla oblongate to pons vatoli to mid brain then to thalamus.
Third neuron
- impulse travels from the thalamus to the sensory cortex.
Explain the bodies natural pain relief
Endorphins from the experience are opiate-like peptides (neuropeptides) produced naturally
in the body at neural synapses in CNS pathways
▪ How they work:
– They bind to presynaptic membrane, and inhibit the release of
substance P (inhibit the transmission of pain).
– Substance P is a neurotransmitter that is ‘liberated’ at some
synapses when there is a pain impulse that facilitates information
about pain which is then transmitted to higher centres.
Name some techniques which activate peripheral sensory receptors
Superficial hot or cold - compresses / hot packs /cold face washer
▪ Hydrotherapy - Showers / baths
▪ Touch & Massage
▪ Acupressure, shiatsu, reflexology
▪ Transcutaneous Electrical Nerve Stimulation (TENS) (interrupts pain pathway)
▪ Water injections
These can actually reduce the pain signals getting to the brain.
List some techniques that enhance descending inhibitory paths
- Support person - therapeutic use of self
- Relaxation - breathing exercises
- Attention-focusing & distraction
- Music
- Aromatherapy
- Therapeutic touch
- Hypnosis
These help labour go smoothly
List some coping strategies for pain
- Reassurance
- Positioning
- Mobility (walking, rocking, swaying)
- Water
- Aromatherapy
- Music
- Heat packs
- Massage
- trust between provider/partner/support person and mother
- stay up right (sitting, kneeling, standing, leaning forward and squatting)
- intradermal water injections
- heat packs
- massage
- counter pressure
- transcutaneous electrical nerve stimulation (TENS) machine
List and explain some pharmacological pain relief
Nitrous oxide
- breathed in just during contraction
- something for women to focus that is rhythmic
Pethidine/Morphine
- can have resp depression in baby when born
- reduces awareness of the pain
Epidural
- lots of interventions occur when this is started
Name the 3 instances when a abdominal palpation may be helpful and what it would assist in finding
Admission assessment
- ensure size = dates
- position and engagement
Assessment of progress
- descent of head
- 4 hrly
Prior to VE
- match external findings with internal findings
What are some key practice points fo a VE
- Always after an abdominal palpation
- Often done to assess progress, but when performed by different clinicians can have inconsistent/differing findings
- increase risk of ascending infectionparticularly once membranes have ruptured
- Clinically it is common to perform VE’s 4 hourly, though this is not based on evidence
List some indications for a VE
- Prior to labour as part of determining induction method
- During labour to confirm onset
- Identify presentation and position
- Assess progress
- Perform ARM (artificial rupture of membrane)
- Apply FSE (fetal scalp electrodes)
- Exclude cord prolapse after ROM
- Confirm onset of second stage of labour (particularly for breech presentation or multiple pregnancy)
Contraindications of VE should not be completed!!
- If no consent
- Known placenta praevia or vasa praevia
- Active bleeding
- Suspected preterm labour (<37 weeks- may cause infection or onset labour)
- Pre-labour ROM (may introduce an infection)
List some key points of preparations prior to a VE
- Privacy (curtain, quiet room)
- Explanation (ensure what it intails, feeling, lube, right up at back of vagina)
- Consent (must be informed)
- Empty bladder (very uncomfortable)
- Position woman - semi-recumbent covered with sheet
- Waterproof sheet (bluey / pinky) underneath her
- Sterile gloves and lubricant
