maternal adaptations to pregnancy

list 3 types of placental hormones

1. Steroid hormones -> estrogen and progesterone

2. Peptide hormones -> human chorionic gonadotrophin

3. Prostaglandins -> dilate cervix, cause uterine contractions

estrogen

• Enlargement of the uterus and breasts

• Important for the development of foetus

progesterone

• Develops cells in the uterine endometrium -> nutrition of the early embryo

• Reduces contractility of the pregnant uterus

• Important in the development of the foetus

• Helps oestrogen prepare the mother's breast for lactation

 

steroid hormones act on the pituitary gland to increase production of

prolactin and ACTH

steroid hormones (?)the production of follicle stimulating hormone and lutenising hormone

decrease

ACTH acts on the adrenal cortex to increase (?) secretion

cortisol

healthy weight gain in pregnancy (?kg)

10-12kg → steep increase in weight from week 12 until full term of the pregnancy

weight gain distribution in pregnancy

Total weight gain at 40 weeks → 13kg

Healthy foetus → 3kg

Placenta -> 600g

Amniotic fluid -> 800g

Uterus -> 1kg

Breasts -> 450g

Blood and extravascular fluid → 3kg

Maternal reserves → 3-4kg

appetite increases during pregnancy due to what hormone?

high levels of progesterone acting on the appetite centre of the brain

energy intake increases by (?) per day to ensure proper foetal development

840kj

food cravings

• May be related to the effect of pregnancy hormones

• Can alter likes/dislikes for certain foods

increase in thirst

• Brought about by the action of prolactin and the activation of the renin angiotensin system

• High levels of oestrogen activate the renin angiotensin system

• More angiotensin 2 produced

• Acts on the thirst centre in the brain to increase thirst

basal metabolic rate increases about (?)% in the later stages of pregnancy due to what hormone?

• 15% → due to increase in thyroxine

• increases heat production → pregnant women frequently has sensation of becoming overheated

progressive insulin resistance (cause and effects)

• Caused by increase in prolactin, human placental lactogen, progesterone, cortisol during pregnancy

1. After a meal the mother's glucose concentration increases higher than normal

2. Cells not receiving required glucose -> free fatty acids used as an alternative

3. Glucose crosses the placenta via facilitated diffusion -> insulin resistance has benefits for foetus

glute-1-transporter

• Insulin independent glucose transporter

• Insulin resistance has no effect on the glucose transporter across the placenta

diabetes mellitus

• Insulin resistance in pregnant women usually never reaches a level that it would be diagnosed as diabetes mellitus

• In a small percentage of pregnant women, they develop gestational diabetes mellitus (3-7%)

• Insulin resistance is more severe -> leads to abnormally high blood glucose levels

• Diagnosis usually cleared once baby is born -> insulin resistance falls

blood volume increase % (list 3 components)

• Blood volume → 30-40% (increase in plasma volume + red blood cell mass)

• Plasma volume → 40-50%

• Red blood cell mass → 15-25%

red blood cell mass increase during pregnancy is mediated by what protein?

erythropoietin -> increases due to high levels of human placental lactogen and progesterone which increases erythropoietin secretion

pregnant women are more prone to anaemia caused by (?) deficiency

iron

how is iron excreted from the body? (what is the daily iron requirements for non-pregnant women)

• Iron is lost in the body via cell death

• Dead cells excreted via urine -> 1mg of iron lost per day

• 2mg of iron required in diet per day to develop iron deficiency

iron requirement increases in pregnant women due to (list 2)

• 1mg of iron lost per day

1. Foetus is taking iron from the mother

• Foetus requires 300mg of iron throughout span of pregnancy

2. Increase in mother's red blood cell production

• Therefore mother requires 570mg of iron over the pregnancy period

what is the daily iron requirement for pregnant women? (failure to do so will?)

• 4mg iron required per day

• Twice the amount non-pregnant women need to take

• Failure to do so will result in iron deficiency for mother and foetus

• Tiredness, shortness of breath

• Developmental problems for foetus due to lack of iron in the central nervous system

plasma protein concentration decreases by about (?) - what does this result in?

• Plasma protein concentration decreases by about 20%

• This then reduces the colloid osmotic pressure in the capillaries

• Upsets balance of fluid movement across the capillary walls -> causes swelling 

there is an increase in the synthesis of certain plasma proteins: (list 3)

1. Transferrin → required to deliver more iron from mother to the placenta

2. Hormone-binding proteins → transport hormones in the plasma and deliver them to where they are needed

3. Fibrinogen and other clotting factors → prevent excessive blood loss when baby is born

• However increases risk of venous thrombosis for duration of pregnancy (blood clot forming inside vein)

cardiovascular changes

• Cardiac output increases by about 40-50% due to increase in blood volume

• As well as an increase in stroke volume (also due to inotropic effect of estrogen on the cardiac muscle -> increases strength of contraction -> increases volume per beat)

• Heart rate increases

• Resting heart rate increases to 85bpm in pregnant women (from 70bpm in non-pregnant women)

blood pressure during pregnancy

• We would expect an increase in the mother's blood pressure during pregnancy due to the increase in cardiac output

• However it actually goes down

 

• Mean arterial pressure significantly lower compared to non-pregnant women

• Due to decrease in total peripheral resistance from systemic vasodilation

• Due to increased levels of oestrogen and progesterone

• Both have been shown to increase nitric oxide production in the blood vessel wall 

• Nitric oxide is a powerful vasodilator

 

• Placenta is also producing large quantities of vasodilating prostaglandins -> reduce total peripheral resistance

 

• Blood pressure returns to normal towards the end of the pregnancy

oxygen consumption during pregnancy

1. Extra oxygen is consumed by foetus

2. Heart → due to an increase in demand (increase in heart rate and stroke volume increases energy requirement)

3. Kidneys → activation of the renin angiotensin aldosterone system

• Increase in the active transport of sodium

4. Respiratory system → ventilation increases in the uterine muscle due to the increased size of the uterus -> higher oxygen consumption

5. Breasts → due to increase in size and developmental changes

 6. Placenta requires oxygen

the increasing demand for oxygen during pregnancy is met by (list 3):

• An increase in red cell mass

• An increase in cardiac output

• An increase in ventilation

explain the increase in ventilation to increase oxygen intake during pregnancy (and how the consequences are compensated for by the renal system)

• Increase in ventilation due to increase in tidal volume and respiratory rate due to progesterone acting on respiratory centre

• Results in physiological over breathing -> mother breathing more than she needs to

• Mother blows off more CO2 than she needs to -> arterial PCO2 drops from 40mmHg to 30mmHg

• A drop in arterial PCO2 would incur respiratory alkalosis -> increase in pH

• However, mother's kidneys compensate for this by secreting less H+ ions and secreting more bicarbonate ions -> maintain normal blood pH

flaring of the lungs

• As uterus expands -> diaphragm is pushed up into chest cavity

• We would expect vital capacity to decrease

• Vital capacity increases during pregnancy

• Due to flaring of lower ribs -> subcostal angle has significantly increased

• Flaring effect mediated by oestrogen causing relaxation of the ligaments that hold the rib cage in position

tidal volume (a) in pregnant women, whereas residual volume (b)

(a) increases

(b) decreases

renal changes

• Kidneys increase in size about 30%

• Due to massive increase in blood flow

• Increases glomerular filtration rate by 50%

• Enables mother to increase waste removal (products of metabolism)

usually an increase in glomerular filtration rate would increase fluid loss in urine → why does this not occur in pregnant women?

• Due to the activation of the renin angiotensin aldosterone system via oestrogen (and ADH)

1. ADH increases reabsorption of sodium and water

2. Mother retains salt and water

3. Excretes more waste products

• Angiotensin 2 is released upon RAAS activation -> a powerful vasoconstrictor -> however massive vasodilation occurs

• Angiotensin 2 effects blunted by oestrogen and progesterone

glucose in urine in pregnant women → can lead to what complications?

• Increase glucose levels in urine

• As increase in blood glucose levels in pregnant women means that there is a limit to kidney reabsorption of glucose from the filtrate

• Excess glucose excretion

 

• Urine therefore can become a growth medium for bacteria

• Increases risk of urinary tract infection

 

• Increase in the size of the uterus puts pressure on the bladder

• Results in frequent urination

• Can also result in partial blockage of the ureters -> urine retention in the upper part of the ureters -> increase risk of urinary tract infection

what is the main gastrointestinal change that occurs during in pregnancy

• Decreased smooth muscle tone

1. Increase in progesterone has inhibitory effect on the production of the hormone motilin

• Motilin stimulates gastric and intestinal motility 

• Decreased levels of motilin reduces motility -> increases constipation risk

• Increase fibre intake to counteract this

 

2. Can also cause relaxation of the oesophageal sphincter

• Causes heartburn -> common in later pregnancy when the uterus is enlarging and pushing upwards -> pressure on stomach and oesophageal sphincter -> reflux and heartburn due to reduced tone of sphincter

nausea (morning sickness)

• Starts 1-2 weeks after conception

• Usually disappears after the first 3 months

• Due to increasing human chorionic gonadotrophin which increases very early in pregnancy

• Sign of healthy pregnancy -> pregnant women who experience no nausea during the pregnancy have an increased risk of stillbirth, miscarriages, birth defects

changes in gut microbiome

• Increase in bacterial load in the GIT

1. Increase in proteobacteria and actinobacteria -> associated with inflammation

2. Decrease in faecalibacterium -> anti-inflammatory effects

• Results in pro-inflammatory states

• Glucose intolerance may promote energy storage and foetal growth

• Increased inflammation is beneficial during implantation

changes in vaginal microbiome

• Decrease in microbiome diversity

• Increase in lactobacillus

• These bacteria produce lactic acid

• Creates a barrier against pathogens by maintaining a low pH of les than 4.5

• Lactobacillus also secrete metabolites that inhibit infections and increase vaginal secretions which fosters further lactobacillus growth

changes in oral microbiome

• Increase in pathogenic bacteria

• Including Porphyromonas gingivalis and aggregatibacter actinomycetermcomitans

• These increases the risk of periodontal disease (gum diseases)

• Levels of candida also increase -> increases risk of oral candidiasis

changes in placental microbiome

• Dominated by proteobacteria

• Low microbial density

• Resembles the oral microbiome

• Composition of placental microbiome different amongst women with term verses preterm birth

summary