8.12 Maternal Physiology Flashcards
Give some reasons why their must be pregnancy induced changes in the physiology of the mother
-allow for adaptation to the growing size of the foetus
-provide nutrients to the growing foetus
-remove waste from the foetus
-prepare the body for birth and lactation
What are some endocrine changes in the reproductive system of the mother
The corpus luteum produces oestrogens, progesterone and relaxin. The placenta produces oestrogen, progesterone, relaxin, human placental lactogen and corticotropin releasing hormone.
What are some endocrine changes in the pituitary gland of the mother
The pituitary gland enlarges which can sometimes push on the optic chiasm causing vision issues. Prolactin levels are increased and LH and FSH levels are decreased.
What are some endocrine changes in the thyroid gland of the mother
The thyroid enlarges and serum levels of T3 and T4 can double (as foetus can’t produce its own thyroid hormones at early stages)
What are some endocrine changes in the adrenal gland of the mother
Total cortisol serum levels rise.
Describe 2 mechanisms behind the increase in blood volume (hypervolaemia) during pregnancy
- There are changes to the renin-angiotensin-aldosterone system, oestrogen causes an increase in the production of angiotensinogen from the liver and renin from the kidney. Therefor angiotensin 1 and 2 production is increased which increases blood volume via aldosterone secretion. This causes an increase in blood pressure, however the oestrogen causes vasodilation to compensate for this.
-In pregnancy, the thirst threshold is decreased and ADH levels are increased. This causes blood volume to increase and blood osmolarity to decrease
Describe the effects of hypervolaemia on haemoglobin concentration
Blood volume and red blood cell count both increase independently of each other. However, blood volume increases at a greater rate than red blood cell count, hence haemoglobin concentration decreases. Haematocrit is the ratio of the volume of red blood cells to the total volume of blood.
What are some benefits of hypervolaemia
maintains blood pressure, cools body, meets demands of pregnancy, improved uterine intervilous perfusion, protects against blood loss at delivery
What are some drawbacks of hypervolaemia
can cause hypertension, oedema, altered pharmacokinetics, increased postpartum diuresis
Describe some of the physiological effects of pregnancy on the cardiovascular system
-increase in stroke volume and heart rate causes increase in cardiac output
-decrease in systemic and pulmonary vascular resistance, preventing blood pressure surge, thought to be caused by increased sympathetic tone and sensitivity to catecholamines
-as foetus grows, heart is pushed upwards and heart volume increases
-vena cava and aorta are compressed by foetus, mothers are sometimes tilted to unblock inferior vena cava, moving from the left lateral recumbent position to the supine position leads to a decrease in cardiac output through supine hypotension
Describe some of the physiological effects of pregnancy on the renal system
-kidney is the primary excretory organ for foetal waste, hence increased intravascular and extravascular volume for kidneys
-increase in metabolic waste products
-60% increase in glomerular filtration rate
-can lead to glucosuria and aminoaciduria (glucose/amino acids in urine), which can be measured with dipsticks
-high prevalence of overactive bladder
-many drugs are excreted in urine, so with increased GFR, drug dosages may need to be increased
Describe how pregnancy affects ventilation
Total lung capacity is slightly reduced as the foetus pushes upwards on the diaphragm. Inspiratory capacity increases and expiratory reserve volume decreases. The respiratory rate does not change
Describe how pregnancy affects the respiratory system
-hypersecretion of mucous in upper respiratory tract
-Mucosal capillary engorgement
-Oedema of larynx, pharynx and trachea
-Flaring of lower ribs and increase in substernal angle
Describe how pregnancy can affect the mouth in the digestive system
-progesterone stimulates appetite (pica-craving non food substances)
-increased food intake alters oestrogen progesterone glucagon and insulin
-oestrogen increases blood flow in gums, causing the, to be swollen, spongey and increased dental problems
-excess salivation (pytalism) and reluctance to swallow due to nausea
Describe how pregnancy affects the oesophagus to colon in the digestive system
-heart burn
-decrease in gastric acid secretion
-reduced intestine and colonic motility and tone
-reduced gastric emptying
-reduced motilin
Why does the maximum concentration of orally administered drugs increase during pregnancy
due to delayed gastric emptying and prolonged small intestine transit time, vomiting which reduced absorption of drugs, increase in gastric pH increases ionisation of weak acids which prevents their absorption, antacids and iron (commonly taken during pregnancy) can chelate drugs and decrease their absorption
What is morning sickness
Nausea and vomiting caused in pregnancy, its severe form is hyperemesis gravidarum
Describe how pregnancy can affect the pancreas, gall bladder and liver of the digestive system
-tone and motility of gall bladder is decreased by progesterone
-pancreas produces slightly less amylase and lipase, and insulin resistance is greater
-liver is displaced by growing uterus
-storage and mobilisation of liver glycogen is faster
-there is alteration of liver plasma proteins, serum enzymes and serum lipids
Describe the effects of pregnancy on the musculoskeletal system
-progesterone and relaxin cause loosening of ligaments
-changes in calcium, vitamin D, phosphate and magnesium levels can lead to leg cramps, restless leg syndrome, backache, rickets and osteomalacia
Describe the effects of pregnancy on the metabolism
-metabolic rate increases by about 15%
-increase in heat production
-increased energy requirement
Describe the effects of pregnancy on integument
-Increased eccrine sweat gland activity
-Increase in pigmentation
-Linea nigra
-Melasma
-Spider nevi
-Palmar erythema
-Varicosities
-Striae gravidarum
-Pruritis
-Acne
-Hair thickening then loss
