Reproduction session 8 Flashcards
(29 cards)
- Define
Partition
Labour
Delivery
- Parturition = transition from pregnant to non-pregnant state (birth)
- Labour = physiologic process by which a fetus is expelled from the uterus to the outside world -> uterine decidua (internal lining) and myometrium
Changes in the cervix tend to precede uterine contractions
• Delivery = the method of expulsion of the fetus, transforming fetus to neonate
Stages of labour:
First stage - Creation of the birth canal
Two phases:
- Latent Onset of labour with slow cervical dilatation but softening. Lasts a variable time.
- Active Faster rate of change & regular contractions
(• Physiologically – multiple changes resulting in creation of the birth canal and descent of the fetal head into it
• Clinically – interval between onset of labour and full dilatation of the cervix)
Second Stage
- passive – descent and rotation of the head
- active –Maternal effort to expel the fetus and achieve birth
- Physiologically – changes in uterine contractions to expulsive, descent of the fetus through the birth canal and delivery. (adaptations of the fetus)
- Clinically – the time between full (10cm) dilatation of the cervix and delivery.
Third stage
- Physiologically – expulsion of the placenta and contraction of the uterus
- Clinically – third stage starts with the completed birth of the baby and ends with complete expulsion of placenta and membranes
- Usually lasts between 5 and 15 minutes; up to 30 -60 minutes may be normal depending on circumstances and management
Draw a flow chart to show how these stages are initiated
- In humans what promotes labour?
- What produces this substances?
- What stimulates its production?
- Prostaglandins MOA:
- Cervical ripening is due to?
- Increase in O:P ratio & increase PG levels
- PG mainly in myometrium & decidua (mother)
Placenta, decidua, myometrium and membranes can all synthesis prostaglandins
Increased synthesis of prostaglandins by amnion in third trimester
- Increase in oestrogen: progesterone ratio and mechanical damage stimulates prostaglandin synthesis
(higher O:P more PG)
- Powerful contractors of smooth muscle and are also involved in cervical softening
- oestrogen, relaxin & prostaglandins breaking down the CT
- What factors effect contractility of the uterus?
- Action of oxytocin is inhibited in pregnancy by?
Stimulated by?
- What increases the no. Of receptors for oxytocin?
- Pregnancy = increased number of gap junctions to aid communication between muscle cells (coordinates effective uterine activity)
• @ 36 weeks = increased number of oxytocin receptors in myometrium - therefore uterus can respond to pulsatile release of oxytocin from posterior pituitary gland
what allows for the inc no of receptors?
- What increases release of oxytocin? Draw a diagram to explain. What is it called?
- Other factors
- • Progesterone inhibits contractions
• Oestrogen increases gap junctional communication between SM cells – increases
contractility
• Mechanical stretching of uterine smooth muscle increases contractility – as gestation increases
Oxytocin - Initiates uterine contractions
- Inhibit: progesterone, relaxin and low number of oxytocin receptors
Stimulate: Afferent impulses from cervix and vagina
Ferguson reflex
- Acts on smooth muscle receptors – More receptors if oestrogen:progesterone ratio high
- • Cervical stretching releases prostaglandins
- Fetal effects ? – glucocorticoids – placenta – inhibits progesterone
- Fetal oxytocin?
- Infection, bleeding – feed into the central mechanisms triggering contractions
- When do changes in the cervix occur? What changes are made to the cervix (before & after)
- What causes the cervix to change?
- How does the cervix collagen in proteoglycan matrix change in ripening?
- What is this triggered by?
- How does increasing levels of relaxing during pregnancy effect the cervix?
- Stage 1 :
Tough, thick, collagen -> dilation (10cm) , softening, ripening
- oestrogen, relaxin and prostaglandins breaking down the connective tissue.
- – Reduction in collagen
– Increase in glycosaminoglycans
– Increases in hyaluronic acid
– Reduced aggregation of collagen fibres - Triggered by prostaglandins
– PGE2 and PGF2a
in the uterus increase contractility of SM in the cervix cause dilation/relaxation
- collagen : ground substance ratio, enzymes degrade collagen
- Occurs over a period of weeks – evident from 36/40
- Labour cervix offers less resistance to
- presenting part
- Known as effacement and dilatation
- Size of birth canal? (i.e. size of baby head, cervix & pelvic inlet)
- Changes of the pelvic floor,vagina and perineum?
- How is the myometrium specialised for stage 2
(• passive – descent and rotation of the head
• active – Maternal effort to expel the fetus and achieve birth)
- What is the sequence of contractions in the uterus
- The uterine capacity is progressively reduced so
- • In normal presentation
– Head biggest part
– Diameter of presentation 9.5 cm
Cervix 10cm
• Maximum size of birth canal determined by pelvis
– Pelvic inlet typically 11 cm
– Softening of ligaments may increase it
- stretching of levator ani & thinning of the central portion of the perineum transforms to almost transparent membranous structure
- Myometrium -> CONTRACTION & RETRACTION (partially relax + shortening)
- Symmetry and polarity: contractions from two poles of uterus -> fundus -> upper part of the uterus (more powerful) -> lower segment (less powerful)
- pressure inside uterus increases
- How does the generating force in the myometrium start?
- Control of contractility?
- – Much thickened in pregnancy
– Force when intracellular [Ca2+] rises
– Due to action potentials
– Triggered spontaneously ‘pacemakers’
- • Contractions made more forceful & frequent by – Prostaglandins
- More Ca2+ per action potential – Oxytocin
- More action potentials – Lower threshold
3.
How do we describe the position of the fetus
Lie, attitude, presentation
LAP
Give further detail of lie
Longitudinally or transverse
Give further detail of attitude
Ef of - extension
flexion - fuck of
How can a baby present?
Buttocks out or feet first and head is
- Principles of inducing labour
- How can the physiology of the fetus be monitored during labour
- Movements in the second stage of labour?
- How can delivery be facilitated by intervention?
- • Stimulate release of prostaglandins – membrane rupture
- Artificial prostaglandins
- Synthetic oxytocin
- Anti-progesterone agents
- • Monitoring the fetus – compare with observations on any patient – but indirect
- Consider the whole picture – the maternal-placental-fetal unit
- Heart rate patterns
- Maternal temperature
- Colour & amount amniotic fluid
- Scalp capillary pH
SCALP = HAT on fetus SCALP H-HR A-amniotic fluid T- temp of mum
- • Head flexes, Head rotates internally (towards sacrum), “crowning” (head stretches perineal muscle and skin) (eyes looking at ass), extension of head and external rotation/ restitution (you nose sniff the ass, you extend head away so you rotate back to normal)
- Shoulders rotate
- Shoulders deliver (right before left i think)
- Followed rapidly by the body
- Cesarean Section, Operative delivery (forceps/ vacuum)
A. Separation and Descent of the Placenta, how does it occur ?
- Control of Bleeding: (3)
- Normal blood flow through site is ? (10-15% of cardiac output)
A.• Baby born - marked reduction in size of uterus due to powerful contraction and
retraction (ongoing)
- Size of placental site therefore reduced (can be up to ½ before separation begins)
- Inelastic placenta is squeezed by contraction
- • 1. Powerful contraction/retraction of uterus especially action of interlacing muscle fibres (“living ligature”) which constrict blood vessels running through the myometrium
- Pressure exerted on placental site by walls of contracted uterus (apposition – once placenta and membranes delivered)
- Blood clotting mechanism (sinuses and torn vessels)
- 500-800 ml/minute
Immediate changes in physiology enabling fetus/neonate to adapt to independent life
Neonate takes first breath
– Multiple stimuli
• Trauma
• Cold
• Light
• Noise
CVS:
- Clamping the umbilical cord results in closure of the Ductus venosus
- On taking a first breath, tissue resistance decreases in the lungs
- Vascular resistance decreases and blood flows to lungs
- It becomes oxygenated and pulmonary pO2 rises
- Net drop in pressure on the right side of the heart, higher pressure in left atrium closes Foramen ovale
- This pressure imbalance results in a temporary reversal of flow through the Ductus arteriosus and its muscle wall contracts in response to increased pO2 closing it
Respiration
- First breath causes lungs to expand
- Alveoli inflate
- Inflation maintained by surfactant
- Regular breathing enabled by neonatal brain pathways triggered at birth
- Resuscitation of newborn based on knowledge of physiology and biochemistry
Expulsion of the fetus requires a no. Of processes
What is the Apgar score?
Definition of post partum and importance?
- What does post natal care entail?
- What does post natal examination entail?
- midwives must visit not less than 10 days post delivery - up to 28 days post delivery
The health visitor also has a statutory responsibility for allnot less than 10 days infants under five years of age in a given residential area and will usually visit the woman at home between day 10 and 12 postpartum and then encourage the mother to attend local baby
clinics once a week until the baby is approximately 6 weeks of age.
The health visitor then takes over responsibility for the child until he/she is five years of age. The community midwife has a responsibility of care to the woman until 28 days postpartum and, therefore, will visit her or advise regarding care if there are any complications or concerns.
- approx. six weeks after delivery by the GP or by the obstetrician if the antenatal period or delivery have been complicated. By six weeks postpartum most of the pregnancy-induced changes in maternal physiology have returned to normal and it is an appropriate time for assessing the mother-infant interaction.
Examination:
- woman’s mental and physical health + feeding and behaviour of the baby.
- urinary, bowel and sexual function as incontinence and dyspareunia or anxiety about sexual intercourse are issues that many women will not discuss voluntarily.
- Blood pressure, urinalysis and a general, breast, abdominal and pelvic/perineal examination is performed to ascertain that the uterus has involuted adequately and that any perineal trauma has healed.
- A cervical smear is also taken if it is due and contraception is discussed, if it has not already been initiated. The postnatal examination is an excellent opportunity to discuss with the mother her adjustment to parenthood and any anxieties she may have.
ANATOMICAL AND PHYSIOLOGICAL CHANGES (11)
-
Lower genital tract- these are secondary to low oestrogen levels
- Reduction in size of vulva, vagina and cervix
- Poor lubrication of the vagina
- Transformation zone of the cervix withdraws into the endocervix
- Internal os is closed - Bleeding- initial heavy flow= lochia rubra
- Changes from red-brown/red-pink-heavy white (lochia alba)
- Duration of bleeding is variable, only 1:10 women still bleeding at 6/52 post partum
- Passage of clots is not normal, except for the one passed on D3/4
- Endometrium regulates
- If no lactation, new endometrium by 3/52, 1st period due by 6/52
- If lactation, ovarian activity suppressed, therefore menses delayed by several months
-
Skeletal muscle- devarication of the recti, resolves depending on pre-pregnancy laxity,
parity, level of physical activity - Skeleton- ligament laxity resolves
- Cardiovascular function- the increased PR (by 15bpm) at term and increased cardiac output reverses by 6/52
What happens to haemoglobbin, serum ferritin, wbc and platelets post partum?
- The early puerperium in the hours after birth may be characterised in some women by a postnatal ‘high’. A degree of elation is obviously normal, especially if the woman is satisfied with her birth experience and has a close partner and family that are supportive and congratulatory.
Positive feelings in the puerperium include: - Negative feelings may include:
- satisfaction
an increased closeness to her partner
an increased closeness to her own mother
a gradual ‘falling in love’ with the baby
a feeling of protectiveness towards the baby
changes in the relationship with the marital partner: now ‘mother
and father’ and not just ‘husband and wife’. - dissatisfaction, disappointment or distress over the delivery process
anxiety about the baby
rejection or ambivalence about the baby
jealousy about the baby being the centre of attention
fears of harming the baby
physical discomfort and anxiety about physical damage during birth
overwhelming responsibility
resentment at loss of freedom
reactivation of poor relationship with own mother leading to anxiety about repetition through generations.
ONSET AND MAINTENANCE OF LACTATION
1.a ? cause hypertrophy in pre-existing alveolar-lobular structures in the breast. There is also formation of new alveolae by budding from the milk ducts, with proliferation of milk-collecting ducts
B. Although there are high levels of lactogenic hormones (prolactin and placental lactogen) in pregnancy, only minimal amounts of milk are formed, because
MILK PRODUCTION AND SECRETION
2a. Prolactin levels and milk production are dependent to the frequency and duration of suckling. Prolactin levels are at their highest in the early puerperium (period of 6 weeks post natal) and reduce slowly, only returning to normal after weaning.
Milk secretion is also dependent on adequate emptying of the secreting glands. Accumulation of milk inside the alveoli will cause distention and atrophy of the glandular epithelium. Therefore, adequate milk secretion requires an intact neuroendocrine axis and
adequate emptying of the breast with infant feeding.
- DELIVERY OF THE BREAST MILK
A. Oxytocin, contraction of the myoepithelial cells situated around the alveolae expel the milk into the milk-collecting ducts. These ducts have longitudinal muscle cells, which are also stimulated, causing them to dilate and improve the free flow of milk towards the nipple along these dilated ducts.
b. This leads to the ‘let down’ reflex. Oxytocin is released in response to a variety of sensory inputs including suckling, seeing or hearing the baby but is also readily inhibited by emotional stress or anxiety. There also seems to be a 90 minute cycle of ‘let down’
irrespective of suckling, because oxytocin is released in a pulsatile manner from the pituitary.
As lactation is initiated, the volumes are low and colostrum is
initially produced. This has a high fat content and is also high in
immunoglobulins. As suckling continues, the amount of milk
increases until, when fully established, approximately 800 ml per
day are produced.
a. Progesterone, oestrogen, prolactin, growth hormone and adrenal steroids
b. oestrogen & progesterone inhibit their effects. Prolactin is released by the action of suckling at a nipple that has become exquisitely sensitive post delivery.
