Physiology Pregnancy Flashcards
During what days of fertilisation does the blastocyst move to uterus?
day 3-5
During what days of fertilisation does the blastocyst attach to the lining of the uterus?
Days 5-8
What do the inner and outer cells of the blastocyst become?
Inner cells become embryo and outer cells burrow into uterine wall to become placenta
How does the blastocyst implant into the uterine wall?
Cords of trophoblastic cells begin to penetrate the endometrium, advancing cords then tunnel deeper into endometrium to carve out hole for blastocyst & boundaries between trophoblastic cells disintegrate and decidua forms
What tissues is the placenta derived from?
Trophoblast and decidual tissue
How does the corpus luteum help with implantation?
Makes more progesterone than oestrogen to make low oestrogen:progesterone ratio which is necessary for implantation
At what day does trophoblast start producing HCG?
Day 8
Around what week (and what trimester) does HCG peak?
Week 9 so in trimester 1
When does corpus luteum shrivel up and stop producing hormones?
Week 13 - end of first trimester
What type of cells of the placenta take over hormone production after corpus luteum, and what do they produce?
Syncytiotrophoblast cells and they produce progesterone, estriol, little bit HCG, and Human Placental Lactogen (hPL)
How does the body compensate for uterus pressing on diaphragm during pregnancy?
Progesterone relaxes ligaments of the thorax to increase transverse and anterioposterior diameter of ribcage
hPL is produced from about week 5. What is the function of hPL AKA human chorionic somatomammotropin? (3)
To counteract the effects of maternal insulin to leave enough glucose in blood for baby,
has growth hormone-like effects so promotes protein tissue formation,
is involved in breast development
At what week gestation does uterus reach umbilicus?
20 weeks
At what week gestation does uterus reach xiphoid process?
36 weeks
What is the fundal height and what does it measure?
Distance from pubic symphsis to top of uterus, measures size of baby so checks size with gestational age
Why does BP slightly fall during pregnancy?
Progesterone causes vessels to dilate
Pregnancy is a high volume state. By how much does blood volume increase during pregnancy and what component increases most?
between 30-50%, plasma increases a lot (50%) while rbc’s increase less (25%) so physiological anaemia of pregnancy
Why does heart rate increase by about 20 BPM in pregnancy?
To pump the high volume of blood around
Why can pregnancy cause varicose veins?
Uterus presses on pelvic veins so blood can back up, causing varicose veins and swelling in lower legs and ankles
How can pregnancy cause hypotension when lying down?
Uterus can press on inferior vena cava and so less blood can get to RA
Why does eGFR and urinary output increase in pregnancy? By how much does it increase and when does this peak?
Due to increased CO and increased bloodflow to kidneys and pressure on bladder from uterus. By 30-50% and peaks 2nd trimester
What is physiologic hydronephrosis and physiologic hydroureter?
Physiological response of kidneys and ureters to increased volume, calyces, renal pelvises and ureteres increase in size to compensate
What is pica?
Craving for non-food items e.g. ice
What causes GI symptoms (gastric reflux and heart burn, constipation and bloating) in pregnancy?
Hormonal changes cause relaxation of lower oesophageal sphincter and cause smooth muscle relaxation of intestines and decreased peristalsis
Why are pregnant women more prone to upper UTIs?
Due to progesterone causing hypomotility of ureters and increased capacity to store urine leading to renal stasis
Increased tidal and minute respiratory volumes in pregnancy lead to decreased CO2 and a mild respiratory alkalosis. What does this mild alkalosis enhance?
Enhances gas exchange with placenta
What causes nasal stuffiness, sinus congestion and nosebleeds during pregnancy?
Oestrogen causes increased vascularisation and capillary engorgement of upper resp tract
What causes the waddling gait of pregnancy?
Progesterone and relaxin from the placenta loosen the SI joint and symphysis pubis
What causes breasts to grow (ductile system and development of lobule-alveolar system) in pregnancy and feelings of breast tingling, fullness and tenderness?
Oestrogen - ductile system, progesterone - development of lobule-alveolar system. Increased blood flow can cause those symptoms.
What does each placental villus contain and what is its function?
Each villus contains fetal capillaries separated from maternal blood by a thin layer of tissue. The function is 2 way exchange of gases, nutrients and metabolites down diffusion gradient
By what week of pregnancy is placenta and fetal heart functional?
Week 5
Outline placental development
Trophoblasts differentiate into syncytiotrophoblasts (multinucleated cells) which invade decidua and break down capillaries to form cavities filled with maternal blood. Developing embryo sends capillaries into syncytiotrophoblast projections to form placental villi.
What hormone stimulates anterior pituitary to secrete prolactin for milk and what hormone inhibits prolactin during pregnancy?
Oestrogen stimulates anterior pituitary and progesterone inhibits prolactin
What causes the areola and linea alba to darken and become linea nigra during pregnancy?
Melanocyte-stimulating hormone from the anterior pituitary
What causes pregnancy to be a prothrombotic state?
Oestrogen promotes blood clotting by increasing plasma fibrinogen, activity of coagulation factors and decreases activity of antithrombin III
What does progesterone stimulate the decidual cells to secrete?
Glycogen, proteins and lipids
What are two main actions of HCG?
Maintains corpus luteum and so keeps it producing progesterone & causes the male fetus to develop sex organs
How does the placenta act as a physiological arteriovenous shunt?
The placenta develops villi into uterine wall which blood vessels from embryo develop within. A thin membrane separates the embryo’s blood in the villi from the mother’s blood in the intervillous space so there is no direct contact of fetal and maternal blood. The arteriovenous shunt is formed by the circulation within the intervillous space
___ diffuses from maternal into the fetal circulation system through maternal (oxygen-____) blood and the umbilical blood (mixing of arterial and venous blood, oxygen-____) ____ follows a reversed gradient.
Oxygen, oxygen-rich, oxygen-poor, CO2
Fetal, oxygen saturated blood returns to the fetus via the ________ ____ and maternal, oxyge-poor blood, flows back into the _______ ____.
Fetal - umbilical vein, Maternal - uterine veins.
What are the three factors that facilitate oxygen transport in the foetus?
- Foetal Hb: increased ability to carry O2.
- Higher Hb concentration: 50% more Hb in foetus than adult
- Bohr effect: foetal Hb can carry more oxygen in low pCO2 than in high pCO2
Through what 4 transport mechanisms can nutrients and waste products cross the placenta and give an example of each.
simple diffusion (fatty acids), osmosis (water and electrolytes), simplified transport (glucose) and active transport (calcium, iron and vitamins)
Iron and Ca2+ only go from foetus to mother. True/false?
False - can only go from mother to foetus
What is the function of progesterone in pregnancy? (3)
development of decidual cells, decreases uterus contractility, preparation for lactation
What is the function of estrogen in pregnancy? (3)
enlargement of uterus, breast development and relaxation of ligaments
HCG serum levels double every ___ hours in a singleton early pregnancy. Levels fall from __ - __ weeks. Side effects are ___ and ___. High levels caused by ____ & ____ pregnancies. ____ pregnancy would give static or slow rising & ____ pregnancy would give falling.
48hrs, 12-14 weeks, side effects nausea and vomiting, high levels multiple and molar pregnancies, ectopic static and failing falling
ECG changes, functional murmurs and additional heart sounds are all normal ECG changes in pregnancy. True/false?
True
CO decreases in last 8 weeks of pregnancy as becomes sensitive to body position e.g. uterus compresses vena cava. By how much does it increase again during labour?
Increases 30% more
WHO definition of anaemia in pregnancy is Hb < ___g/L in 1st trimester and Hb < ___g/L in 2nd and 3rd trimesters.
1st trimester - <110g/L
2nd and 3rd trimesters: <105g/L
How does the body lower CO2 levels during pregnancy?
Resp rate increases (progesterone signals brain to lower CO2) & tidal and minute volume increases (O2 increase to meet metabolic need) so pCO2 decreases slightly while PO2 doesn’t change
What 2 factors cause increased re-absorption of ions and water from the kidneys in pregnant women?
increase in placental steroids and increase in aldosterone production
How does each position affect renal function?
Upright, supine and lateral when sleeping
Upright - decreases, supine - increases and lateral sleeping - really increases
What biochemistry markers do we have lower reference ranges for in pregnancy due to increased plasma volume and increased GFR?
ALT, urea, creatinine and albumin
Outline how hypertension and gestational diabetes can be caused by the release of CRH form the placenta.
CRH stimulates ACTH release by mother which stimulates aldosterone and cortisol secretion. Aldosterone can cause hypertension if lots produced. Cortisol causes oedema and insulin resistance so may cause gestational diabetes
What hormones produced by the placenta can cause maternal hyperthyroidism?
HCG and HC thyrotropin
What is the cause of hyperparathyroidism in pregnant woman?
Ca2+ demands
What is average weight gain in pregnancy?
11kg
What tissues cause weight gain in pregnancy in order of most to least?
fetus, body fluid, extra-embryonic fluid/tissues, uterus, breasts, fat accumulation
How much extra calories and extra protein intake per day does a mother need during pregnancy?
200 extra kcal/day and 30g/day extra protein
1st-20th week is _____ phase of mother and the foetus has quite ____ nutritional demands. 21-40th week is _____ phase of mother and the foetus has quite ____ nutritional demands
Anabolic phase, foetus low demands, catabolic phase, foetus high demands
What changes occur in the mother’s anabolic phase?
normal/increased sensitivity to insulin, lower plasmatic glucose level, lipogenesis, glycogen stores increase and growth of breasts, uterus and weight gain
What changes occur in the mother in the catabolic phase of pregnancy?
AKA accelerated starvation. Maternal insulin resistance, increased transport of nutrients through placental membrane and lipolysis
What hormones cause insulin resistance in mother?
HPL, cortisol and growth hormone
List 5 special nutritional needs in pregnancy.
folic acid, vitamin D supplements, high protein, iron supplements and B vitamins for erythropoesis
What hormonal ratio changes to increase excitability of uterus towards end of pregnancy?
Oestrogen:progesterone changes - oestrogen increases contractility and progesterone inhibits contractility
Prostaglandins, oxytocin and mechanical stretch of uterine increase contractility and excitability of uterine towards end of pregnancy. Where are prostaglandins produced and where is oxytocin produced?
Prostglandins produced by placenta, myometrium, decidua and membranes. Oxytocin produced by maternal posterior pituitary gland
What are Braxton Hicks contractions?
Mild, irregular contractions practicing for labour
What changes occur in the cervix towards the end of pregnancy and what causes these changes?
cervical ripening (i.e. softening) by oestrogen, relaxin and prostaglandins that break down cervical connective tissue & stretch of cervix by fetal head
What two cervical changes increase uterine contractility at labour?
cervical stretching causes increased contractility and causes further oxytoxin release
How do strong uterine contractions and pain from birth canal cause intense abdominal muscle contractions?
The contractions and pain cause neurogenic reflexes from spinal cord that causes abdo contractions
What is the role of oestrogen from ovaries in initiation of labour?
Induces oxytocin receptors on uterus
What is the role of oxytocin in initiation of labour?
stimulates uterus to contract and stimulates placenta to make prostaglandins
What is the role of prostaglandins in initiation of labour?
Stimulates more vigorous contractions of uterus
What is the 1st stage of labour and approx. how long does it last?
Cervical dilation - lasts approx 8-24hrs
What is the 2nd stage of labour and approx. how long does it last?
Passage of foetus through birth canal - lasts approx. few mins to 120mins
What is the 3rd stage of labour?
Expulsion of placenta
What stimulates the milk-let down reflex and what are the steps of this reflex?
Receptors in nipples stimulated by baby sucking, impulses sent to spinal cord, hypothalamic nuclei stimulated by spinal cord reflex, oxytocin then released by posterior lobe of pituitary gland and then milk ejected
Outline the pathway that causes lactation.
Sound of child’s cry stimulates higher brain centres, this stimulates hypothalamus to secrete oxytocin to eject milk and also inhibits PIH (prolactin inhibiting hormone) cell causing decreased PIH so increased prolactin and so increased milk production
