Pregnancy Flashcards
What is the gestational age
Used clinically
Time zero - first day of last menstrual period
Expressed in completely weeks plus days
What is the embryonic age
Used in embryology
Time zero = fertilisation
Expressed in days or ongoing weeks
When does implantation occcur
Begins day 6/7, complete by day 10 after ovulation
What are the 3 stages of implantation
apposition, attachment and penetration
What is the inner layer of the trophoblast
composed of mononuclear cells and is known as cytotrophoblast
What is the outer layer of the trophoblast
multinucleated cells and is known as syncytiotrophoblast - makes hCG
What is the role of hCG
feeds back to corpus luteum which is making progesterone, which then maintains pregnancy (positive feedback loop). Endometrium becomes deciduliased (dilating blood vessel in the presence of NK cells).
What are recurrent miscarriages
3 or more sequential miscarriages with the same partner.
What happens at Day 12 after implantation
extraembryonic structures develop from extraembryonic endoderm and then cavitates. Embryo getting nutrition by diffusion.
What happens at Day 13 after implantation
primitive amniotic cavity forms. Primitive yolk sac is pinched off.
What is the end of the second week of implantation characterised by
first appearance of chorionic villi
How is the chorion leavae formed
the villi on the decidua capsularis pole degenerate
How is the chorion frondosum formed
Villi adjacent to the decidual plate rapidly grow and expand
How is the placenta formed
Chorion frondosum and decidual plate
When do spiral arteries open
Spiral arteries open (closets to the embryo) during the first trimester. Dilated but plugged by cytotrophoblast. These plugs break down for intervillous flow. 6 weeks post conception to see on USS
What happens if spiral arteries fail to open
pre-eclampsia occurs (high blood pressure, systemic condition characterised by proteinuria). Failed adaption to paternal antigens in the placenta.
How can pre eclampsia be picked up on uterine artery doppler screening
Should be continuous flow in diastole. Pre-eclampsia, pattern will be same as in non-pregnant women (absent flow at the end of diastole.
When is aspirin given for pre-eclampsia
Aspirin given before 16 weeks to reduce risk. Have to be given before gestation
What are the characteristics at the end of the fourth month
placenta has attained its definitive form.
Maternal portion formed by the decidual plate and a fetal portion, made by the chorion frondosum
Amniotic membrane and chorionic membrane (closest to the placenta)
Maternal circulation 500ml/minute
Average blood loss at delivery is 300-500 ml
What happens when cleavage occurs before implantation
Dichorionic
What happens when cleavage occurs 6-8 days into implantation
Monochorionic, diamniotic
What happens when cleavage occurs after day 8
Monoamniotic
What is chronionicity
Number of gestational sacs
What is gastrulation
Formation fo the 3 layers fo the embryo
When is the first sign of polarity notices
14 days = formation of primitive streak (bottom) and buccopharyngeal membrane (head
What does the ectoderm comprise
epidermis, hair, nails, nervous system, mammary glands (carcinoma)
What does the mesoderm comrpise
connective tissue, musculoskeletal system, gonads (cancers are sarcomas)
What does the endoderm comprise
epithelial lining GI and resp tracts and bladder, liver, pancreas
What is sacrococcygeal teratoma
Tumour in newborns in the coccyx. Causes heart failure
What do ectodermal dysplasias cause
inability to sweat, teeth do not form
What is Hirschprung’s disease
Neural crest disorder: absence of nerves in the colon. Forms toxic megacolon.
What happens in the fourth emboryonic week
neurulation
Cranial neuropore closes D25 (non-closure is anencephaly, lethal), caudal neuropore closes D27 (non-closure is spina bifida)
What is holoprosencephaly
failure of forebrain to divide and develop. Associated with other midline and facial defects, Tri 13. Severity varies
What is cardiogenesis
canalisation of cardiogenic clusters in the mesoderm results in the formation of the paired heart tubes.
How does the GI system develop
Primitive gut tube differentiates to foregut (temporally closed by the oropharyngeal membrane until 4th week. Blood supply for celiac artery), midgut (connected to yolk sac until 5th week), and hindgut (temporally closed by cloacal membrane, which ruptures in the 7th week)
Midgut rotates 90 degrees counter clockwise around the axis of the SMA and the umbilical cord. 10th week, midgut retracts back into the abdomen and rotates a further 180 degrees
What is omphalocoele
often coexists with T18. Intestine are outside body, covered by a thin layer of tissue.
What is gastroschisis
gut is outside and parallel. Isolated defect. More common in young women.
What does VEGF do
Cause proliferaiton of blood vessels
When is the brain most susceptible
10 weeks onwards
How does the placenta develop
develops over the entire surface of the chorion and then regresses to form the discoid placenta
When do arterial plugs disappear and what happens
12 weeks of pregnancy. As plugs disappear, oxidative stress and therefore apoptosis increases. Plugging coincides with period of histotrophic nutrition.
What are the functions of the placenta
Respiratory organ
Nutrient transfer
Excretion of fetal waste products
Hormone synthesis
What causes foetal growth restrictin
can be caused by inability to trophoblasts to erode arterial plugs
Once placenta is abnormal, reversal is not possible
Early delivery will be needed
What is placenta abruption
Placenta coming away from uterine wall
Describe the nutrient transport system i nthe syncytiotrophoblast
GLUTs - predominately GLUT-1 active transporter
FATPs
Lipases cleaving NEFAs from TAGs, which are then transported across the trophoblast cells by FATP
AA transporters: system A, system L and taurine transporter
Describe the placental gas exchange
Foetus umbilical arteries: higher pCO2 than foetal umbilical vein as excess CO2 is taken by maternal circulation. pO2 is foetus is low (1/3 of mother) - creates concentration gradient
How is CO2 transported
facilitated by carbonic anhydrase enzyme
What is the foetal alimentary tract
intestinal villi formed by 16 weeks and well developed by 19 weeks. Gut development important for amniotic fluid homeostasis. Gastrin, motilin and somatostatin regulate growth and development - present in gut by 13 weeks. Digestive enzymes e.g. disaccharides present by 9-10 weeks
When does the foetus synthesise inuslin
9-11 weeks - Determines glucose metabolism. Excess glucose leads to excess growth and fat deposition. Inadequate glucose leads to emaciation
Why is the foetus dependent on mother for glucose
little capacity for gluconeogenesis as enzymes do not function at ambient low pO2
What are smaller babies susceptible to
fewer nephrons in the kidneys. Higher chance of hypertension. ACE inhibitors contraindicated for pregnant women
What is polyhydramnios
Too much amniotic fluid
What is oligohydramnios
Too little amniotic fluid
Describe fluid homeostasis in the foetus
maintained by placenta and foetal membranes. Urine important component of amniotic fluid (0.5L/day). 3% cardiac output to kidney (25% in adult). GFR 50% of adult. Foetal bladder fills and empties every 20-30 minutes.
Why is foetal urine hypotonic
Hypotonic due to immature ADH.
What controls foetal heart rate
Subject to catecholamine, chemoreceptors, barorepctors. Influences act via ANS. PNS tone dominates
What are foetal CV adaptations
umbilical vein and artery, ductus venosus (shunt to bypass liver), foramen ovale (blood to enter left atrium from right atrium), ductus arteriosus (shunt for blood from right ventricle to bypass lungs straight to descending aorta)
What are the changes at delivery
cord occlusion decrease right atrial pressure so foramen ovale closes
Inspiration causes vasodilation (due to NO) of pulmonary artery and decreased resistance in pulmonary circulation reducing flow through foramen ovale and ductus arteriosus
What do NSAIDS do
Accelerate duct closure
What do PGE2 and prostacylcin do
Delay duct closure
What does increased arterial pO2 do
Closure of ductus arteriosus
What do T1 alveolar cells do
Surface area
What do T2 alveolar cells do
Secrete surfactant - decrease surface tension and stabilise the lung. Secreted from 30 weeks
What happens in surfactant deficiency
neonatal resp distress syndrome. Increased work of breathing, decreased lung compliance, alveolar collapse
What happens in late pregnancy rise in cortisol
stimulates surfactant synthesis and secretion. Epithelial cell differentiation. Lung liquid reabsorption. Increases activity of anti-oxidants
Describe foetal Hb change
gradual switch to HbA from 28 week. 80:20 ratio at birth. HbF has higher affinity for O2 due to lower sensitivity to DPG.
What are the stimuli for first breath
Asphyxia of normal birth Physical manipulation and compression Cold shock Visual stimulus Gravity
What is the mean weight gain in pregnancy
12kg
What are the changes to maternal RBCs
Erythropoietin stimulates increased synthesis
Number increases but apparent anaemia due to dilution
Haematocrit falls from 40% to 32%
Approx 30% increase in DPG facilitating offloading of O2 release
What increases in pregnancy
Anything lipid or lipid soluble increases in pregnancy
What decreases in pregnancy
Anything water soluble
What occurs with folate deficiency and why
deficiency causes spina bifida. Folate is required for DNA synthesis for bases (purines and pyrimidines). Also important for DNA methylation.
What do oestrogens do
Stimulate synthesis of FA and cholesterol
CV adaptation to pregnancy (peripheral vasodilatation)
Growth of uterus (myometrial cells)
Priming of uterus for labour
Weak anti-insulin activity (via enhanced cortisol)
Cervical ripening
Stimulate RAAS (increases renal sodium reabsorption and thus water retention)
What does progesterone do
Prepared and maintains endometrium to allow implantation
Produced initially by corpus luteum then placenta
May have a role in suppressing the maternal immunological response to foetal antigens thereby preventing maternal rejection of the trophoblast (by decidual NK cells recognising antigens as self)
Plays a role in parturition
Serves as a substrate for foetal adrenal gland production of glucocorticoid and mineralocorticoids
Growth of mammary glands
Maintenance of pregnancy (inhibition of uterine contractility, prevention of ripening of cervix)
Induces over breathing and lowering of maternal CO2
What does hCG do
Rescue and maintenance of function of corpus luteum. About the 8th day after ovulation or 1 day after implantation - hCG takes over for corpus luteum
Survival of the pregnancy is dependent on corpus luteum progesterone until 7th week of prengncy
When does hCG fail to become a good test
10 weeks
What does hCG bind to
TSH receptors of thyroid cells, stimulating thyroid function
What does hPL do
Increase in maternal plasma free NEFAs
Anti-insulin - increase in maternal insulin, favouring provision of mobilisable AA an fetal protein synthesis as well as glucose for transport to the foetus
Potent angiogenic hormone
What does placental growth factor test for
Pre-eclampsia
What is leptin
produced by adipose tissue - inhibits hunger
Secreted by cytotrophoblast and syncytiotrophoblast; maternal levels are significantly higher than in non-pregnant women
Stimulates placental AA/FA transport
Foetal leptin levels correlates positively with foetal birthweight
How does blood pressure change during pregnancy
Total peripheral vascular resistance: decreases (increased NO, prostacyclin, and compliance of vessels due to structural changes)
CO increases
HR increases
Dissecting aortic aneurysm : inner layer of the aorta tears
How does skin blood flow change in pregnancy
Predominately increases in hands and feed
Leads to increase in skin temp, nail growth etc
What are the changes in kidneys in pregnancy
Increase in GFR
Plasma conc of renal function i.e. urea and creatinine decrease
Glycosuria
Calciuria
Urinary frequency increases
Urinary stasis due to dilatation of collecting system
What are the changes in pulmonary function
Tidal volume increases but respiratory reserve volume decrease
pCO2 decreased, pO2 increased, pH unchanged as HCO3 falls
Costal margin and diaphragm altered
What are the changes in coagulation and fibrinolysis
Changes occur to induce low grade increase in coagulability
Factors VII, VIII and X
Increased fibrinogen leads to increased ESR
Decreased fibrinolytic activity
What are the changes in GI
Reduced smooth muscle tone: decrease cardiac sphincter tone, decreased motility and mobility
Associated with biliary stasis, increased gastric reflux
What is the anaemia threshold for pregnant women
Under 110 (commonly due to iron deficiency)
What are the risk factors for gestational diabetes
BMI above 30 Previous macrosomic baby weighing 4.5kg or above Previous GDM Family history of diabetes Minority ethnic family origin
What is the test for gestational diabetes
75g 2 hour oral glucose tolerance test at 24-28 weeks
What is the 3 delay mdle
recognition by women to seek care, assessing care, receiving appropriate care
What is alpha-fetoprotein
marker of liver cancer
What does relaxin do
hormone secreted by the placenta that causes the cervix to dilate and prepares the uterus for the action of oxytocin during labour
When can alkaline phosphatase be raised
raised due to liver problem or due to placenta
Why can pregnancy cause dyspnoea
FRC decreased
What do to if pregnant women is suspected of PE
LMWH safe in pregnancy. Thrombolysis safe in pregnancy CTPA or V/Q scan. Can also use D-dimers (not useful in pregnancy)
What are the endocrine changes in pregnancy
Overactive thyroid: symptoms should predate pregnancy
Cortisol: cortisol binding globulin changes. Cortisol lowest at night.
Absorption of calcium increase, increase PTH
What is Bayes theorem
pre-test probability->screening test->post-test probability
What to do if maternal HIV is suspected
maternal treatment, high risk antenatal care, prevent transmission to neonate
What to do if maternal hep b is suspected
changes antenatal care prevent transmission, neonate receives vaccine
What to do if maternal syphillis is suspected
maternal treatment to prevent congenital syphilis
What is seen in T21
increase nuchal, increased beta, increased PAPP-A
What is seen in T18
increase nuchal, low beta, really low PAPP-A
What is seen in T13
lower increase in nuchal, low beta, really low PAPP-A
When are chromosomal abnormalities detected
Happens between 11+0 to 13+6 gestation by USS
Combined test: foetal nuchal translucency (measures back of foetal neck), maternal serum PAPP-A (lower has increased chance) and maternal serum bhCG (higher has increased chance)
When are foetal abnormalities detected
Between 18-22 weeks. Earlier detection becoming more common. USS: structure review of organ systems.
Baseline rate of major congenital abnormality: 1-2%
Depends on: exact disease and gestation, skills and training, quality of USS, maternal BMI
What can be detected in four chamber view
AV septal defect, hypoplastic left heart syndrome, ventricular septal defect, Ebstein’s anomaly
What can be detected in great vessels view
transposition of the great arteries, tetralogy of fallot, common arterial trunk, coarctation of the aorta
