Pregnancy Physiology Flashcards
What systems undergo adaptations for pregnancy?
Endocrine
Immune
CVS
Resp
Haemotological
GI
Urinary
What is responsible for these maternal adaptations?
HORMONES:
hCG
Oestrogen
Progesterone
Relaxin (softens ligaments)
hPL (involved in fat breakdown for glucose)
What are the adaptations within the immune system in pregnancy?
Fetus= hemi allograft- recognised by the maternal immune system
Placental progesterone changes balance between Th1 cells (cytotoxic) and Th2 cells (non-cytoxic)–> this causes reduction in Th1 and increase in Th2–> provides immune tolerance–> don’t have an immune response to baby
Consequences of pregnancy being an immunosupressed state?
Higher attack rate and severity of certain viral pathogens ie. varicella
May improve certain autoimmune conditions (cytotoxic mediated conditions) e.g.g graves
Adaptations in resp system during pregnancy?
Tidal volume- increases by 30-40%
Minute ventilation- increase by 40-50%
PaO2- increase
PCo2- decrease
Expiratory reserve volume- decrease by 20%
Total lung capacity: decrease by 5% as baby pushes up on diaphragm
Consequences of adaptations in the resp system in pregnancy?
Dyspnea- due to hyperventilation due to increase CO2 production- not major shouldn’t happen at rest
Need to consider pathology if it marked:
Physiological e.g. anaemia
Primary cardiac or resp condition e.g. asthma
Is it an acute condition in pregnancy? e.g. PE, pneumonia, ARDS?
Maternal adaptations in CVS due to pregnancy
Cardiac output increases:
Early pregnancy–> increase volume
Later–> increase HR
Progesterone: smooth muscle relaxation
Causes decreases systemic vascular resistance
Drop in diastolic BP during the first and second trimester of pregnancy
RAAS activated
Leading to increased sodium levels and water retention–> total blood volume increases
Affect of pregnancy on clotting factors?
Increased procoagulants: fibrinogen, factor VIII, vWF)
Decreased anticoagulants (protein s)
Reduced fibrinolysis
Consequences of adaptations in CVS/clotting?
Increase RAAS: peripheral oedema
Change in plasma volume: dilution anaemia
Clotting: hyper coagulable state–> risk of thromboembolic events
Adaptation of Renal system in pregnancy?
Systemic vasodilation= increased renal blood flow:
Increased GFR–> 50%
Decrease serum urea and creatinine by 25%
Decrease PCT absorption:
Glucosuria
Structural: smooth muscle relaxation + obstruction
Increased size of kidneys R>L
Decreased speed of urine passage- cause stasis–> more UTIs
Maternal adaptations in GI system when pregnant?
Structural- gravid uterus displaces the bowel- can cause mechanical obstruction
Slow transit due to progesterone effects and increased water absorption- constipation
LFTs: ALP increased due to placental synthesis
Decreased LES tone- GORD, Aspiration
Decreased gallbladder contractility: Gallstones
Maternal adaptations in endocrine system in pregnancy?
Fetus reliant on maternal thyroxine until 8-12 weeks–> takes up a lot of free thyroxine
Increased oestrogen results in increase of hepatic production of TBG–> more free T3 and T4 bind to the TBG–> more TSH to be release–> free T3 and T4 increases but total stays the same
Maternal adaptations in endocrine system in pregnancy?
Fetus reliant on maternal thyroxine until 8-12 weeks–> takes up a lot of free thyroxine
Increased oestrogen results in increase of hepatic production of TBG–> more free T3 and T4 bind to the TBG–> more TSH to be release–> free T3 and T4 increases but total stays the same
Maternal changes to glucose regulation?
Pregnancy= diabetogenic
Insulin resistance as need more glucose to shunt to the baby
Increased insulin secretion
Increased risk of ketoacidosis
Why is there insulin resistance in pregnancy?
As need more glucose to shunt to the foetus
Increase in human placental lactogen, prolactin, cortisol levels- ANTI-INSULIN HORMONES–> increase resistance
Maternal MSK adaptations in pregnancy?
Change in centre of gravity-
Increase lordosis and kyphosis
Forward flexion of neck
Stretching of abdo muscles
Impede posture
Strain paraspinal muscles
this causes: back pain, shoulder pain, tension headaches
Increased mobility of sacroiliac joints and pubic symphysis
Anterior tilt of pelvis
causes pelvic pain
Fluid retention can compress structures e.g. median nerve (carpal tunnel)
Where does the placenta come from?
Begins to develop in the second week of development
Provides nutrients and support for early embryo
Is a type of foetal membrane
What happens in week 2 of gestation/
2 distinct cell layers emerge from:
Outer cell mass- syncytiotrophoblast and cytotrophoblas. Becomes the foetal membrane
Inner cell mass becomes the bilaminar disc: epiblast an hypoblast–> becomes embryo
When does implantation begin?
Day 6
Day 9- conceptus impeded into endometrial wall
What os a chorionic villus?
Placenta is a specialisation of the chorionic membrane
Finger like projections- allow rapid exchange of nutrients
What are some implantation defects?
1) Wrong place: ectopic pregnancy, placenta praaevia
2) Incomplete invasion: Placental insufficiency, pre-eclampsia
What is the decidual reaction?
Transformation of the endometrium in the presence of conceptus–> becomes the DECIDUA–> managed depth of invasion
Decidual reaction provides balancing force for the invasive force of the trophoblast
What happens if decidual reaction is suboptimal?
Can lead to a range of adverse pregnancy outcomes- doesn’t go deep enough–> need depth to be just right
What are the cotyledons of the placenta?
Functional units
Site of distinct villi
Allows transport of metabolites, O2 and nutrients
How does the chorionic villus change as the pregnancy continues?
First trimester- thicker barrier of villi
Third trimester- barrier at optimal thinner
What is the endocrine function of the placenta?
Hormones produced to keep it in place
Protein hormones: Ensures wellness of foetus
hCG
Human chorionic somatomammotrophin
Human chorionic thyrotrophin
Hman chorionic
Steroid: Takes over from corpus lute after 1st trimester
progesterone and oestrogen
What is hCG?
Produced during the first 2 months of pregnancy
Supports the secretory function of the corpus luteum
Produced by syncytiotrophoblast- so pregnancy specific
Excreated in lateral urine- basis of pregnancy tests
Trophoblast disease- cause up regulation–> molar pregnancy and choriocarcinoma
When does the placenta start secreting oestrogen and progesterone?
11th week, takes over from corpus luteum
What is colostrum?
After birth, the breast produce 40ml/day of colostrum
Has less soluble vitamins, fat and sugar than mature milk but contains more proteins particularly immunoglobulins and fat soluble vitamins
What hormone regulates milk production?
Prolactin
How does breast milk initially develop?
During pregnancy, high progesterone:oestrogen favours development of alveoli (in the breasts) but not secretion.
When placenta is removed, source of the previously circulating steroids (mainly progesterone), is removed which is allows alveoli to respond to prolactin.
Breast milk begins to form with 24-48 hours
How is prolactin stimulated in breast-feeding?
Stimulated by suckling–> mechanically stimulates receptors in the nipple–> signals to brainstem to reduce dopamine and increase vasoactive intestinal protein (this promotes prolactin secretion)
What is the milk let-down reflex?
Babies do not suck milk out of the breast, it is EJECTED via the milk let down reflex.
Suckling–> oxytocin released in response–> stimulates the myoepithelial cells that surround the alveoli to contact–> squeezing milk out of the breast
This reflex can be conditioned–> cry or sight of the infant may cause the let down, pain or embarrassment may inhibit it
How do you maintain milk production?
Sufficient suckling to maintain prolactin secretion and to remove accumulated milk.
If suckling stops–> milk production ceases gradually
