Placenta, Parturition, Pregnancy Flashcards
Which part of the blastocyst produces the positive pregnancy test?
Syncitiotrophoblast, outer layer of trophoblast produces hCG which signals to corpus luteum to continue producing progesterone until placenta is developed enough to take over
What are the aims of implantation?
Anchor placenta
Establish basic unit of exchange between fetus and mother- chorionic villus
Establish maternal /fetal blood flow within placenta
Describe formation of chorionic villus
Primary villus-syncytiotrophoblast penetrated by cords of cytotrophoblast day 13
Secondary villus penetrated by fetal mesenchymal cells day 15-16
Tertiary villus-penetrated by fetal vessels: Chorionic villi day 23
Stalk attaching fetus to placenta forms umbilical vessels
What further changes occur to the chorionic villus during development of the pregnancy?
Thinning of placental barrier
Margination of fetal vessels
Massive expansion of surface area by arborisation
What is the name for coiled up chorionic villi?
Cotyledons
What changes occur to the Feto-maternal interface/ interhaemal distance as the pregnancy progresses?
Up to week 20: 4 layers - Syncitiotrophoblast, cytotrophoblast, mesoderm, capillary endothelium
After 20 weeks: 2 layers - Syncitiotrophoblast, capillary endothelium
Describe the Early stage formation-day 6/7 of the placenta
Blastocyst-inner cell mass / trophoblast - forms placenta
Establishment of placenta takes precedence
Invasion of endometrium-day 7
Syncytium-outerlayer
Cytotrophoblast-inner layer
Decidual reaction-limits invasion/initial nutrition/QA
Describe the structure of the umbilical cord
2 umbilical arteries-deoxygenated blood from fetus
1 umbilical vein-oxygenated blood-from mum
Helical
Wharton’s jelly
30-90cm
Describe the Maternal –fetal bloodflow system and what factors can affect it
Low pressure / high flow
500-750ml/min at term
Factors-fetal heart / vessels
umbilical vessels
uteroplacental flow- mumHow many placentas will there be in a dizygotic pregnancy?
2 placentas or fused
dichorionic diamnionic
How many placentas could there be in a monozygotic twin pregnancy?
Splits very early: dichorionic/diamnionic
Before day 9: monochorionic/diamnionic
After day 9: monochorionic/monoamnionic
What are the functions of the placenta?
Endocrine: steroid and peptide hormones
Transfer: Nutrition / waste / gas exchange
Immunity
What are the peptide hormones secreted by the placenta?
Human chorionic gonadotropin: Peaks at 10-12 weeks, Maintains corpus luteum, Basis of pregnancy tests
Human placental lactogen-hPL: Rise steadily during pregnancy, Glucose metabolism
What steroid hormones are secreted by the placenta?
Progesterone: maintains uterine quiescence, maternal adaptations, suppresses HPO
Oestrogen: Substrate for increased maternal oestriol is in fetal adrenal gland
What forms of transport and transfer does the placenta do?
Governed by MW, solubility, charge Simple diffusion, Facilitated diffusion, Active transport Pinocytosis / transcytosis
Which molecules move across the placenta by simple diffusion?
Gases-O2 /CO/ CO2
Water
Electrolytes
Urea and uric acid-waste products
Which molecule moves across the placenta by facilitated diffusion?
Glucose
Which molecules move across the placenta by active transport?
Amino-acids
Water soluble vitamins
Iron
What is pinocytosis? And which molecules are transported across the placenta in this way?
Receptor mediated transcytosis
Engulfed into cytoplasm of the trophoblast
Extruded into fetal circulation
Globulins, phospholipids, immunoglobulins
Describe the immune function of the placenta
Most antibodies of the IgG group cross readily
Receptor mediated pinocytosis
Passive immunity
IgG in fetal circulation exceeds concentration in maternal circulation as term approaches
What dysfunctions can occur with the placenta?
Position / Development: Inappropriate site-ectopic, praevia, Abruption, Uncontrolled invasion- accreta, increta,percreta
Growth: Uncontrolled growth, Gestational trophoblastic disease, Molar / choriocarcinoma
Transport bad stuff: Smoke, Drugs-eg, cocaine, Alcohol-Fetal alcohol syndrome, Infectious agents-eg, rubella, Antibodies-Rh disease
Blood flow compromised: Inadequate placentation, HTN &pre-eclampsia, maternal vascular disease, IVC compression, maternal haemorrhage / hydration
What is placenta praevia?
Placenta implants low down close to cervix
Risk of major haemorrhage during delivery
What is Abruption of the placenta?
Trauma or cocaine
Rips Placenta off attachment
What is placenta accreta, increta and percreta?
Uncontrolled invasion of the placenta
Accreta: into myometrium
Increta: outside uterus
Percreta: into abdomen, other organs
What types of placent praevia can occur?
Marginal
Low lying
Complete
What types of Abruption could occur?
Revealed
Concealed
Concealed and revealed
What blood flow dysfunction could occur with a placenta? What could be consequences of this?
Inadequate placentation: HTN &pre-eclampsia
Impairment: maternal vascular disease, gestational age, post dates
Mechanical: IVC compression
Volume: maternal haemorrhage / hydration
Consequences: fetal growth restriction / fetal compromise / fetal death
What is a marker for dysfunction in foetal blood flow?
Amniotic fluid volume
What happens to the placenta as it ages?
Placenta matures to meet increasing demands of fetus
Surface area increases
Interhaemal distance decreases
Ultimately may be exceeded, post dates
When is the placenta delivered?
3rd stage of labour, afterbirth. Controlled cord traction to get it out
Inspection
Why is dating a pregnancy important?
Monitor normal progress of pregnancy (both for mum & baby)
Educate mum / reassure / expectations
Early detection of problems in mum or baby / intervention
Prepare mum / family / health care team
Know if pregnancy is too short / possible prematurity
Know if pregnancy is too long / post dates
What dates are normal for pregnancy?
Term: 37-41 completed weeks Preterm: 24-37 weeks Post term: > 41 weeks Three trimesters Embryonic period first 8 weeks, Foetal period 8 weeks to term
What are methods of dating a pregnancy?
LMP: Naegele’s Rule Early sono: CRL crown rump length Symphysio –fundal height from PS to fundus Later sono: BPD bi parietal diameter UK standard is BPD at 12 weeks
What are flaws to pregnancy dating?
Overweight lady measurements would be difficult
Not accurate in twins
What anatomical changes occur in pregnancy?
Mechanical effects as uterus enlarges
Compression of multiple structures: Bladder / Ureters, Gut, Diaphragm / Lungs, Heart / Aorta / Vena cava
Skin / Muscle stretching
Lumbar spine exaggerated lordosis
Why do we use a wedge when measuring pregnant ladys blood pressure?
Compression of aorta & IVC in supine position
What hormone changes occur in pregnancy?
First trimester: Human chorionic gonadotropin, morning sickness
Second trimester: Progesterone dominates/ oestrogen also high
Progesterone= Smooth muscle relaxant so Ureters-Dilated, Bladder-less tone, Gut-delayed peristalsis, full stomach, Decreased vascular resistance, fall in BP, Skin-pigmentation, Dark nipples, linea nigra
Human placental lactogen: glucose metabolism
Prolactin: preparing for lactation
Give an overview of antenatal care
Early visits: Establish due date, Check medical history, Check OB history, Discuss lifestyle
Later visits: Monitor maternal adaptations / changes, Monitor foetal growth & development, Educate / advise / prepare
Throughout pregnancy there should be identification of risk factors that could affect maternal and foetal outcomes
What is reflective functioning in pregnancy? And how can it be assessed?
Mother’s imagined relationship with her baby
Look at mother’s mental representations of unborn baby using Working Model of the Child Interview
When do Maternal Representations of the Developing Foetus occur?
During antenatal period pregnant women build up maternal representations or images of their developing foetus
Particularly apparent between the fourth and seventh month of gestation when foetal movements can be felt by pregnant women
What factors can affect a women’s reflective functioning and maternal representations of their unborn baby?
Biological changes
Psychological factors
Social factors including environment and relationships of mother to be
What maternal representations do women who suffer domestic abuse have? And what is the significance?
Have more negative representations of their developing foetus
Babies more likely to be insecurely attached once they are born
What does the Working Model of the Child Interview do? What are the domains that women can be divided into?
Identifies whether women are Balanced, Disengaged or Distorted
Balanced: can provide richly detailed, coherent stories about experiences of their pregnancies and positive and negative thoughts and feelings about their foetuses
Disengaged: uninterested in foetus or their relationship with it and demonstrate few thoughts about the babies future traits and behaviours or themselves as mothers
Distorted: tend to digress or express intrusive thoughts about their own
experiences as children, often viewing their foetuses as an extension of
themselves or their partners
Why are maternal representations important?
Stable over time so women with distorted or disengaged prenatal representations still have them at 1year post-partum
Predict observed parenting behaviours and child attachment at 12 months
Highlights need for identification of unplanned pregnancies, substance abuse, domestic violence and unresolved parenting so that women can be supported through early intervention
What is Intergenerational Transmission of Trauma?
Trauma and neglect in childhood have effects that last throughout life course
Ghosts in the Nursery: process by which traumatised children become
unresolved parents who then re-enact trauma they experienced with their own baby. Result of parent’s mental representations of their child and the way they act towards their child
What is ghosts in the nursery?
Ghosts from parent’s childhood invade the parent-infant relationship by unconsciously influencing the way parents think about and behave towards their baby
Parents enact with their baby, scenes from their own unremembered, but painfully influential early experiences of helplessness and fear
What are unresolved parents?
Carry issues from their childhood that have not been addressed
May be less able to parent because infants distress triggers their own stress and painful memories of vulnerability and dependence
Unable to respond to infant in terms of his or her current functioning
Unable to mentalise about distress of their infant and make inaccurate assumptions about the reasons for such behaviours, For example, might suggest that baby is crying to annoy her or describe the baby in critical and inappropriate terms (she is evil)
Unresolved parents tend to become very withdrawn or very intrusive in their parenting
How can parents go from unresolved to resolved?
Need opportunity to address issues from their childhood
Need help to learn how to mentalise
What is mentalisation?
Ability to understand mental state of oneself and others which underlies overt behaviour
Ability to understand actions of oneself and others as meaningful because they are underpinned by intentional mental states such as personal desires, needs, feelings, beliefs, and reasons
What is resilience?
Dynamic process encompassing positive adaptation within the context of significant adversity
What is a key source of resilience in early life?
Secure attachment to at least one primary caregiver, or a stand-in caregiver
What is Angels in the nursery?
Process by which children acquire protective experiences despite a wider context of abuse which enables them not to re-enact the abuse with their own children
This happens in moments of particular connectedness which enable the child to identify with a loving parent, and so enables the child when they become a parent not to re-enact other traumas that they may have experienced
What systems undergo major maternal adaptations?
CVS Respiratory Urinary / renal Blood Glucose Metabolism
What adaptations occur to the cardiovascular system in pregnancy?
Occur early- by 12-16 weeks
Heart Enlarges, Apex displaced up and laterally
Increased output up to 6.0 L/min /more in labour
Rate increases 10-15bpm
Stroke Volume increases
MAP falls by about 10mmHg, rises to normal as term approaches
Vascular resistance falls
What antenatal checks can be performed for cardiovascular system?
Hx of CVS disease
BP check at every visit
When is cardiac output highest in pregnancy?
Right after delivery due to release of aorta-caval compression and uterine contraction (autotransfusion)
What adaptations occur to the respiratory system in pregnancy?
Rib cage and breast enlargement
Diaphragm pushed cranially- changes in lung volume
↑ mucosal engorgement due to plasma volume expansion, nasal epistaxis
Increased respiratory rate / maternal awareness/ mild respiratory alkalosis
What antenatal checks would you do for respiratory system?
Hx of respiratory disease
Smoking
What is normal acid base status for a term pregnant lady?
Respiratory alkalosis with metabolic compensation
What adaptations occur to the urinary system in pregnancy?
Increase in renal size
Changes in RAAS Promote plasma expansion (Na + water retention)
Renal plasma flow and GFR are increased
Creatinine Clearance is increased
Renal indices are lower (creatinine / BUN)
Lower absorption thresholds / glucose / protein
Increased risk of infection; dilated ureters /stasis/
What antenatal checks would you do for the urinary system?
Hx of renal disease
UA urinalysis
C&S culture and sensitivity
What adaptations occur to the blood in pregnancy?
Plasma Volume expands 45%
Red cell mass expands by 15% so Hb conc / Hct / RBC fall
Physiologic / dilutional anaemia by 28-34 weeks
Toleration of blood loss is increased for delivery
Many coagulation changes, generally pregnancy is pro-thrombotic
What antenatal checks would you do to check blood?
Weight oedema nutrition Feanaemia labs advice travel Hx of thrombosis
What are average blood losses during delivery?
600 ml with vaginal delivery
1000ml with C/S
Maternal adaptation allows gravidas to tolerate haemorrhage better before showing a drop in BP
PPH still occurs
What adaptions occur to glucose metabolism in pregnancy?
Pregnancy is diabetogenic due to placental hormones (Placental lactogen, HGH, cortisol, progesterone)
Increased appetite/ fat deposition
Insulin resistance increases in pregnancy and levels rise
Post prandial glucose levels increase
Facilitates transfer to baby
Adaptive capacity of pancreatic insulin output may be overwhelmed Gestational diabetes
What antenatal checks would you do for glucose metabolism?
Risk assessment
screening for GDM
UA urinalysis
nutrition
What is gestational diabetes Mellitus?
Appears in 4% of pregnancies
Not enough insulin to counteract diabetogenic hormones which increase in pregnancy
Obesity also increasing in the population
Tends to recur in future pregnancies
Increases risk for type 2 DM later in life
Increases risk to baby of macrosomia
What is pre eclampsia?
Systemic disease
Failed adaptation to pregnancy
Linked to inadequate placentation
High blood pressure: Failure of reduced vascular resistance, Failure of renal adaptation to pregnancy
Proteinuria: Leaking of glomeruli
Odema: Leaking of capillaries with increased volume
Which groups are more at risk of pre eclampsia?
Young or older gravidas
Higher incidence in primigravidas
What can result from pre eclampsia?
Maternal and / or foetal compromise and death
What antenatal checks can you do for pre eclampsia?
Risk factors BP at every visit in same position Urinalysis check for PROTEIN Symptom advice / education Check weight and oedema
Describe CO2 removal from the foetus
Maternal hyperventilation stimulated by progesterone
Maternal pCO2 falls
Facilitates placental transfer of CO2 by simple diffusion
Foetus cannot tolerate higher pCO2 than mother, Acid-base problems
Describe oxygen and CO2 movement in the foetus
Oxygenated blood arrives at foetus in umbilical vein
Delivered to venous side of foetal circulation
Foetus must cope with low pO2 blood arriving in wrong place
What shunts are present in the foetal circulation?
Ventricles work in parallel rather than in series
Preferential flow of blood
Ductus venosus: Around liver
Foramen ovale: Flow from inferior vena cava directed selectively to left atrium
Ductus arteriosus: Pulmonary artery to aorta, Distal to branch to head
How do we monitor the foetal cardiovascular system?
Structure Rate Responsiveness Timing Flow: umbilical artery flow doppler
What circulatory adaptations occur after birth?
After first breath: pulmonary vascular resistance decreases causing left atrial pressure to rise above right atrial pressure, closing foramen ovale
Ductus arteriosus contracts due to high pO2 sensitivity of smooth muscle
Both shunts close within minutes after birth. Complete closure normally occurs within a few weeks
Ductus venosus remains partially open but closes with two-three months after birth
Describe foetal lungs and their development
Thin walled air sacs for gas exchange Surfactant to reduce surface tension and allow sacs to expand 4 stages of development Pseudoglandular: 5-17wks Canalicular: 16-25wks Terminal sac: 24-40wks Alveolar: upto 8 years
What is the function of foetal lungs? And what significance does this have for a preemie?
Foetus makes breathing movements irrigating lungs with amniotic fluid (diaphragmatic)
Surfactant produced by type II pneumocytes increase significantly after 30 weeks
Surfactant deficiency in pre-term infants can cause respiratory distress
How do we monitor Foetal lung development?
Foetal Breathing movements
Amniotic fluid analysis: look for surfactant levels
Outline the main features of development of the foetal nervous system
At 8-10 weeks: Local stimuli evoke response Swallowing:10 w Breathing Movements :12-16 w Ability to suck: 24 w Integration of nervous and muscular function increase rapidly in third trimester Hears sound: 24-26 w Eye sensitive to light: 28 w Mum feels movements 18-20 weeks
How do we monitor foetal nervous system?
Foetal movements
Foetal responses
Foetal position / posture / tone
Outline the development of the foetal GI system
Swallowing: 10-12 w
Peristalsis and transport of glucose: 10-12 w
Amniotic fluid volume regulated by swallowing
Hydrochloric acid and digestive enzymes: stomach and small intestine, early fetus
Movement of fluid in GI enhance growth and development of GI tract
Outline the development of the foetal urinary system
Pro and mesonephros degenerate by 11-12w
Failure to form or regress result in anomalies
Between 9-12 w, ureteric bud and nephrogenic blastoma interact to
produce metanephros
14 w, loop of Henle functional
Kidneys start producing urine at 12 w
