5: Physiology of pregnancy and the peurperium Flashcards
After fertilisation, zygotes divide into a ___ and then a ___.
morula
blastocyst
What part of the blastocyst
a) implants in the uterus and becomes the placenta
b) becomes the foetus itself?
a) Trophoblast layer
b) Inner cell mass
Where does fertilisation occur?
Ampulla of the uterine tubes
Where does implantation occur?
Body of the uterus
Which layer of the uterus is invaded by trophoblasts?
Endometrium
What are the outer cells of the blastocyst called?
Trophoblasts
Why do trophoblasts invade the endometrium?
To make space for the blastocyst
While the trophoblasts carve out a space in the endometrium for the blastocyst, what develops in the inner cell mass?
Amniotic cavity
where the foetus itself will develop
What is the decidua?
Endometrium during pregnancy
What is the chorion?
Outer layer of the embryo
whatever that’s called at the time
Which cells break down maternal capillaries to form cavities filled with maternal blood?
Syncytiotrophoblasts
What structures extend from the placenta into the endometrium to exchange gas and nutrients with the maternal blood?
Chorionic / placental villi
What is another name for placental villi?
Chorionic villi
sampled for genetic analysis
What stops foetal and maternal blood from coming into direct contact?
Thin membrane of chorionic villi
By which week in development are the placenta and foetal heart functional?
Week 5
The framework of the placenta i.e foetal/maternal gas and nutrient exchange via chorionic villi is in place by Week 5.
How does the embryo survive before this?
Trophoblasts have invaded the endometrium
Endometrium is highly concentrated with protein, glycogen and lipids
Which hormone, released by the corpus luteum, stimulates the endometrium to concentrate glycogen, protein and lipids?
Progesterone
Which structure extends projections into the endometrium to supply the foetus with nutrients and oxygen?
Placenta
During development, the foetus’ lungs are deflated.
Which structure plays the role of the lungs?
Placenta
What are the relative oxygen concentrations of the maternal and foetal blood?
Maternal blood - greater oxygen concentration
Foetal blood - less oxygen because arterial and venous blood mixes in the placenta
So diffusion occurs from mother to child
What are the relative carbon dioxide concentrations of the maternal and foetal blood?
Maternal blood - less carbon dioxide
Foetal blood - more carbon dioxide
So diffusion occurs from foetus to mother
What blood vessels are contained in the umbilical cord?
2 umbilical arteries
1 umbilical vein
Why does the umbilical cord have two arteries?
Unknown
deal with it
Which vessel carries oxygen-rich blood from the placenta to the foetus via the umbilical cord?
Umbilical vein
Which vessels carry poorly oxygenated blood from the foetus to the placenta via the umbilical cord?
Umbilical arteries
just like the pulmonary arteries and veins, it’s the opposite of normal
Once poorly oxygenated blood has returned to the mother FROM the foetus via the umbilical arteries, which vessels carry it to the maternal IVC?
Uterine veins –> Internal iliac veins –> Common iliac veins –> IVC
Once deoxygenated blood has passed from the foetus to the mother via the umbilical arteries –> placenta, which blood vessels carry it to the maternal heart?
Uterine veins –> Internal iliac veins –> Common iliac veins –> IVC
What is the main difference between foetal and maternal haemoglobin?
Foetal Hb has a greater oxygen affinity than adult Hb
Why does foetal Hb have a greater oxygen affinity than adult Hb?
Foetal haemoglobin interacts less with 2,3-diphosphoglycerate (2,3-DPG)
2,3-DPG shifts the oxygen-Hb dissociation curve to the RIGHT i.e less affinity
So less interaction with 2,3-DPG shifts the curve to the LEFT i.e greater affinity
Foetal blood has an (increased / decreased) concentration of Hb compared to adult blood.
increased concentration of Hb
What is the Bohr effect?
CO2 displaces oxygen from Hb
So increased concentrations of CO2 means decreased affinity of Hb for oxygen
In relation to pregnancy, what is the double Bohr effect?
Remember that increased CO2 conc. = decreased affinity of Hb for oxygen
Foetus exchanges CO2 with mother via placenta - foetal Hb has GREATER affinity for O2 due to decreased CO2 conc.
Mother accepts CO2 from foetus via placenta down concentration gradient - adult Hb has REDUCED affinity for O2 due to increased CO2 conc
The displaced oxygen from adult Hb is exchanged with the foetus via placenta
Double Bohr effect
What three factors re: Hb allow for oxygenation of the foetus during pregnancy?
1. Foetal Hb oxygen affinity > Adult Hb oxygen affinity (reduced interaction with 2,3-DPG, shifts curve to the left)
2. [Foetal Hb] > [Adult Hb]
3. Double Bohr effect
The foetus obtains all the nutrients it requires from the mother via the placenta.
Toxic substances can also cross the placenta - what are some examples?
Drugs e.g thalidomide, tetracycline, anti-epileptics
Alcohol, nicotine, caffeine…
Which hormone prevents the degeneration of the corpus luteum?
hCG
Also the hormone used in the pregnancy test
Which hormone has important functions re: growth and contributes to gestational diabetes?
hCS
human chorionic somatomammotropin
Which hormone is produced by the corpus luteum and allows the endometrium to proliferate?
Progesterone
Which hormone, released by theca cells, allows the uterus to enlarge and the breasts to develop during pregnancy?
Oestrogen
which is a group of different hormones
Why can hyperthyroidism occur in pregnancy?
hCG levels increase in pregnancy
hCG has a very similar structure to TSH; binds to thyroid receptors producing a (mild) effect
> HYPERTHYROIDISM
In pregnancy, the oxygen demand of the mother and foetus increase due to the new foetal circulation.
What cardiovascular adaptions does the body make to account for this?
Blood volume –> Cardiac output increases
Heart rate increases
Blood pressure decreases
What supplement do some pregnant women, and definitely those with multiple pregnancy, require?
Iron
What is pre-eclampsia?
Pregnancy-induced hypertension, proteinuria and oedema
Caused by compression of the spiral arteries during pregnancy
What is the triad of signs seen in pre-eclampsia?
Hypertension
Proteinuria
Oedema (esp. hands and feet)
If untreated, what does pre-eclampsia progress to?
What are the signs and symptoms?
Eclampsia
Hypertension, seizures, coma
Lethal to both mother and baby
How is pre-eclampsia managed?
Regular monitoring of BP, hepatic and renal function, foetal growth
Anti-hypertensive medication - labetalol
Early delivery - 36-38 weeks, can be vaginal or caesarean section
How is labetalol administered?
IV in hospital
PO otherwise
What is the only definitive treatment for (pre)eclampsia?
Delivery
Pregnant women (gain / lose) weight.
gain weight
Do pregnant women need to “eat for two”?
No
250-300kcal extra per day is sufficient
Which hormones increase insulin resistance in pregnant women and may cause gestational diabetes?
Human chorionic somatomammotropin (hCS)
Cortisol
GH
Which supplement is given to pregnant women to prevent neural tube defects?
Folic acid
What dose of folic acid is recommended for most pregnant women?
400 micrograms
What dose of folic acid is recommended for pregnant women at increased risk of delivering babies with neural tube defects?
5 milligrams
Which vitamin supplement is advised for all pregnant women?
Vitamin D
40 micrograms / day
Which supplement is advised in some pregnant women, e.g multiple pregnancy, to prevent anaemia?
Iron
Which specific gland secretes oxytocin?
Posterior pituitary gland
Which hormone reduces uterine contractility?
Progesterone
Which hormones increase uterine contractility?
Oestrogen
Oxytocin
What physical stimulus increases uterine contractility?
What does this mean for multiple pregnancy?
Stretching of the uterus
Twins/triplets/multiples take up more space, increasing the chances of early labour
What are Braxton Hicks?
When in pregnancy do they begin?
Small contractions
2nd trimester
Which chemicals are involved in the induction of labour?
Prostaglandins
Which
a) hormone
b) hormone-like chemical
c) muscle actions
are involved in labour and childbirth?
a) Oxytocin
b) Prostaglandins
c) Uterine contractions
Which structure follows the baby after birth?
Placenta w/ umbilical cord
needs snipped
High levels of which hormones inhibit milk production during pregnancy?
Oestrogen and progesterone
Once childbirth has occurred and the levels of oestrogen and progesterone drop, which hormone can stimulate milk production?
Prolactin
Which structures produce
a) oestrogen
b) progesterone
c) prolactin
d) oxytocin?
a) Theca cells
b) Corpus luteum
c) Anterior pituitary gland
d) Posterior pituitary gland
In terms of breastfeeding, which hormones trigger the
a) production
b) ‘let down’
of the milk?
a) Prolactin - milk production
b) Oxytocin - milk ‘let-down’
Which hormone is responsible for the milk let-down reflex?
What social process is it also responsible for?
Oxytocin
Love / bonding
so breastfeeding and birth release floods of oxytocin, encouraging mother-child bonding
What is colostrum?
First breast milk produced by mammals post birth
High in protein and immunoglobulins
Low in fat (in humans)
What is parturition?
Childbirth
