Pregnancy and Delivery Flashcards
When are the three trimesters in pregnancy and how are they defined?
3 trimesters (defined by experience rather than scientific basis)
1st – 0-13 weeks (30-60% are not successful)
2nd – 13-26 (95% pregnancies successful from here) 26 weeks earliest NATURAL survival at birth
3rd – 26-39 (39-41 weeks is term)
What major changes occur in the first trimester?
Altered immune system Altered emotional state Altered brain function Altered hormones Altered appetite – GI Imbalance
(Uterus presses on GI tract in later trimesters reducing appetite, 1st trimester instead presents with morning sickness)
What major changes occur in the second trimester?
Increased blood volume
Increased blood clotting tendency
Decreased blood pressure
Altered fluid balance
What major changes occur in the third trimester?
Altered joints (increased flexibility) Increased weight
What is the role of hCG in pregnancy? When does it peak?
HCG binds to corpus luteum mimicking LH to ensure continued release of progesterone and oestrogen.
8 Weeks peak
(Levels coincide with morning sickness)
What happens to levels of the main pregnancy hormones?
Placental lactogen - Rises continually, acts as GH for the foetal development
Oestrogens - Rises continually, becomes dominant in delivery
Progesterone - Rises continually, remains dominant until delivery
What are the terms used to describe the various stages of an unborn baby?
Conceptus – baby, placenta, foetal membrane, umbilical cord
Embryo – Baby before species distinguishable
Foetus – Baby for remainder of pregnancy
Infant – Baby after delivery
What are the different time keeping systems used in embryological development and clinical pregnancy? Why are these used?
Embryological development measured from fertilisation for accuracy.
Clinically pregnancy is measured last day of menstruation
This only becomes clinically relevant in the case of determining the actually age on infants born pre-term for likelihood of survival etc.
What are the purposes of the placenta?
Separation Exchange Biosynthesis Immunoregulation Connection
SEBIC
What are the functional subunits of the placenta? What are their features?
Functional subunit = Cotyledon
Irregular shape (Resemble gyri in brain) but often called semi-circular. Larger in centre than at periphery
Cotyledon highly branched – high surface area (11m2)
Very effective transport of molecules
What is unusual about the placental vessels? Why does this occur?
Umbilical arteries – Deoxygenated
Umbilical vein – oxygenated
(Think of the umbilical vessels like the pulmonary vessels with same set up - blood leaves the heart to be oxygenated via the mother’s oxygen supply and therefore returns oxygenated)
What is the Cytotrophoblast shell? What is its purpose?
The cytotrophoblastic shell is the external layer of cytotrophoblasts from the fetus that is found on the maternal surface of the placenta
It blocks spiral artery from placenta (if broken down
before ~8 weeks, maternal blood pressure will destroy placenta and result in miscarriage)
Limits oxygen – prevent free radical formation in early embryo
What can placental malformation result in?
Miscarriage in late 1st trimester or 2nd trimester
Pre-eclampsia (Early delivery)
Foetal growth restriction
How common are the various outcomes of pregnancy?
Miscarriage - 350k annually within 13 weeks, 7000 late miscarriages (<23 weeks)
Term (37-41 weeks) births – 700k annually
Preterm (23-37 weeks) birth – 80k annually 45k preterm labour 35k preterm emergency caesarean
(Cause of preterm emergency caesarean – Severe gestational hypertension and other life threatening conditions)
What are Braxton-Hicks contraction?
‘Practise’ contractions that may be experienced by mothers throughout pregnancy, although usually in the later trimesters. It is thought that these sporadic uterine contraction may assist the uterus in preparing for delivery.
NOT EVERY MOTHER WILL EXPERIENCE THESE
What are the phases of labour?
Phase 1 – contraction and cervical changes (MANY HOURS) Longest in first pregnancy
Phase 2 – Baby delivered (FEW HOURS)
Phase 3 – Placenta delivered (30 mins)
What initiates full-term and preterm labour?
Term - Poorly understood
Pre-term: Intrauterine infection Intrauterine bleeding Multiple pregnancy Maternal stress Others
What are the processes that occur in labour?
Cervical ripening and effacement
Co-ordinated Myometrial contraction
Rupture of foetal membranes
(All of these are inflammatory responses)
What changes occur in cervical ripening and effacement?
Change from rigid to flexible structure
Loss of ECM
Recruitment of neutrophils
Prostaglandin E2 and IL-8 released to do this
Paracrine changes IL-8
What occurs in co-ordinated myometrial contractions
Fundal dominant contractions to cervix
Increased power and co-ordination of contraction
Controlled by chemical mediators
(Prostaglandin F2alpha (Foetal E2) from foetal membranes, Oxytocin receptors increased and contraction associated proteins)
Oestrogen dominance is what causes upregulated production of prostaglandins
What changes occur in the rupture of foetal membranes?
Loss of strength, changes in amnion basement component Leukocyte recruitment (Exacerbated in preterm labour) Increased MMP (Matrix metalloproteinase) levels and activity Prostaglandins and ILs mediate
What pro-inflammatory transcription factor is a major component in initiating labour?
NF-kappaB
What pro-inflammatory products are produced in labour
COX-2, IL-8, IL-1beta, MMPs, Oxytocin r, PG r, Contraction-associated genes all involved, and all have NF-kB binding domains in their gene promotors, suggesting its importance
What are thought to be some mechanisms involved in full-term labour?
PGE2 synthesis is constitutive during labour - Inflammatory activity
PAF – platelet activating factor produced in lung surfactant (If surfactant high, high levels and indicates that baby will be able to breathe so delivery can start) upregulates inflammation in foetal membranes
CRH levels increase sharply in labour upregulates inflammation in membranes and also stimulates foetal pituitary to produce ACTH – produce cortisol in adrenals. Cortisol travels through placenta and drives CRH – positive feedback
THINGS THAT INCREASE CRH AND CORTISOL PRODUCTION (E.G. MULTIPLE PREGNANCIES OR MATERNAL STRESS INCREASE THE INFLAMMATION – PRETERM BIRTH)
IL-1beta also produced in full-term labour.
Why does progesterone remain high but labour still occur in human pregnancy?
Progesterone receptor binds to NF-kB prevent inflammatory cascade preventing labour
PR-B able to mediate this
PR-A less able to mediate
PR-A rises at term, PR-B falls at term – functional progesterone withdrawal even though levels remain high
What is a breech birth?
When the baby is facing head up, will causes complications in delivery
