Maternal Physiological Changes During Pregnancy Flashcards
When do changes start during pregnancy? How are these changes controlled?
Most changes begin early (before pregnancy is even recognised)
Most changes are hormonally driven (Progesterone, oestrogen, renin-aldosterone, cortisol, insulin, human placental lactogen, prolactin)
Some mechanically driven (decreased lung capacity, vena caval compression)
What are the changes in physiology of a pregnant mother designed for?
To optimise conditions for foetus and prepare the mother for delivery.
What changes occur in the uterus during pregnancy?
Heigh + weigh (hyperplasia)
Uterine ligaments (stretch and hypertrophy)
Right dextro-rotation (tilts and twists to the right)
Lower segment (formed from isthmus during third trimester and reaches 10cm by term)
What changes occur in the cervix during pregnancy?
Becomes oedematous and congested
Eversion of columnar cells
Increased cervical gland secretion
Mucus plug (operculum)
What changes occur in the vulva during pregnancy?
Increased vascularity and varicosities.
What changes occur in the vagina during pregnancy?
Increased vascularity and distension at birth.
What changes occur in the ovary during pregnancy?
One ovary corpus luteum
Increased vascularity and size
What changes occur in the pelvic ligaments during pregnancy?
Relaxation of ligaments
Relaxation of pelvic joints
Pelvis becomes more mobile and has a larger capacity
What changes occur in the breasts during pregnancy?
Increase in size and vascularity
Increased pigmentation of the nipple
Secondary areola appear
Montgomery tubercles appear on areola (dilated sebaceous glands)
Colostrum expressed from as early as 16 weeks.
What are the endocrine changes that take place during pregnancy?
Pituitary: Increase in size and activity. Posterior pituitary releases oxytocin at the onset of labour and during lactation.
Thyoid gland increases size and activity. TBG levels double. Increase in total T3 and T4 (no change in free T3 and T4)
Parathyroid gland increases in size and activity.
Adrenal gland increases in size and activity and there is an increase in total cortisol.
What could go wrong following labour in the pituitary as a result of post-partum haemorrhage?
Mother becomes hypotensive and so the hypertrophied pituitary isn’t getting enough blood and this results in necrosis thus leading to hypopituitarism.
Why does progesterone drop after birth?
Loss of placenta which produces progesterone.
What do placental oestrogens do?
Induces growth of uterus
Responsible (along with progesterone) for breast development
Alters chemical constitution of connective tissues (more pliable)
Water retention
Decrease sodium excretion
What are the changes that happen to glucose metabolism during pregnancy?
Pregnancy is hyperlipidaemic and glycosuric
After mid-pregnancy insulin resistance develops due to raised cortisol and hPL
Plasma glucose concentration rises (4.5 - 5.5mmol/L)
Glucose crosses placenta (carrier) and is primary energy substrate for foetus
Concentration of glucagon and catecholamines unaltered.
What happens to protein metabolism during pregnancy?
Positive nitrogen balance
On average 500g protein retained by the end of pregnancy.
What happens to fat metabolism during pregnancy?
by 30 weeks 4kg stored in depot fat in abdominal wall, back and thighs, breasts.
Where do pregnanct women gain weight?
3kg in maternal stores of nutrients and muscle development
2kg in increased body fluid (1.5 - 2kg blood)
0.6 kg = Breast growth
1kg Enlarged uterus
1kg amniotic fluid
- 6kg placenta
- 4 - 4kg baby
Total = 11 - 16 kgs
What happens to skeleton during pregnancy?
More lax pelvic joints and ligaments (due to progesterone and relaxin) result in lumbar lordosis
Thorax gets wider
Center of gravity is altered
What happens to urinary system in pregnancy?
Size of the kidneys increases
Ureteral and renal pelvis are dilated by 8 weeks.
There is a decrease in urinary output (1ml/kg/hr)
Increased renal blood flow by 50 - 75%, GFR is higher by 50% and lower albumin in blood means lower colloid oncotic pressure.
What happens to renin production in pregnancy?
It is higher. (stimulated by progesterone)
Where is renin produced during pregnancy? What is the result of this production?
Made in the placenta resulting in net retention of Na+ and excretion of K+
Water retention is 6 - 8 liters.
Decrease in osmolality
Increased glycosuria.
Why does urinary output decrease during pregnancy even though the kidneys are working harder?
Mainly due to increase in aldosterone, progesterone, and oestrogen.
The overall result in an increase in tubular reabsorption.
What is the result of the increased glucose output in urine during pregnancy?
Increased UTIs, pyelonephritis, and oedema.
What are the GI changes during pregnancy?
Increased salivation
Altered taste
Increased appetite and thirst
Slowed Gi motility
Nausea/vomiting (proportional to HCG)
Constipation (decreased motility and increased water + salt absorption)
Decreased gastric acidity.
Relaxation of gastro-oesophageal sphincter resulting in reflux oesophagitis
What causes the relaxation of the gastro-oesophageal sphincter during pregnancy?
Progesterone and relaxin.
What does the liver do during pregnancy?
Increases synthesis of albumin, globulin, fibrinogen, and clotting factors (due to oestrogen)
Increases hormone binding globulins (such as steroids, thyroid, and vitamin D)
Increased gall bladder size and slower emptying (increased tendency for stone formation)
Bile secretion is unchanged
What haematological changes accompany pregnancy?
Increased blood volume
Increased RBC production
Decreased haematocrit (meaning iron supplementation is needed)
Increased WBC production
Decreased platelet production
Fibrinogen as well as all coagulation factors are increased except II, V, and XII
There is a decrease in protein S and sensitivity to APC
Bleeding and clotting time is unchanged
Why are iron supplements needed for women pregnant with twins?
It is impossible for mothers to otherwise keep up with iron needs.
What are the cardiovascular changes seen in pregnant mothers that resemble heart problems?
Heart axis is displaced cephalad and to the left (left axis deviation on ECG)
Murmors in more than 95% (aortic and pulmonary valves)
Rhythm (non-specific ST and T changes and dysrhythmias)
What happens to cardiac output during pregnancy? How does this change take place?
Increase in cardiac output by 30 - 50% (HR higher by 15 - 20 bpm)
Approaching term there is a drop in stroke volume but increase in HR maintains CO
What happens to systemic vascular resistance during pregnancy?
It is decreased as well as peripheral vascular resistance (due to progesterone effects)
BP reaches minimum at 24 - 28 weeks then rises towards the end of pregnancy
Venous return drops and CO drops due to aortocaval compression in T3
Why must pregnant women be tilted at a 30 degree angle for CPR?
Due to compression of inferior vena cava by the uterus (post 24 - 28 weeks caused by uterus being above umbilicus)
What are the overall changes in pregnant mothers’ cardiovascular system?
increased CO and heart rate
Drop in blood pressure.
Aorto caval compresison drops venous return and CO
Uteroplacental flow is ~750ml/min of blood
What happens to oxygen consumption during pregnancy?
It is increased by ~16%
Tidal volume increases (due to progesterone)
Oxygen storage drops
Airway oedema (difficult airway anaesthesia)
Increase in respiratory rate
What happens to mother’s immune system during pregnancy?
Strong cellular immunity
IFN-gamma, macrophage and Cytotoxic TLs are higher in number
Tolerance to non-self MHC (foetus)
Dominance of humoral immunity
IL-10 TGF-beta
Susceptible to infection
Less autoimmunity.
AVOID LIVE VACCINES
What are common skin changes during pregnancy?
Linea nigra
Chloasma gravidarum
Striae gravidarum
(Stretch marks)