Maternal adaptation to pregancy Flashcards
What are the maternal adaptions to pregnacy
Gastrointestinal, metabolic, renal, haematological, immune, respiratory, cadiovascular, endocrine
Explain how maternal adaptations are proactive not reactive
Body rehearses for pregnancy each menstrual cycle, then blastocyst hCG prevents luteal progression
What facilitates maternal adaptations
Two way communication between maternal and fetal tissues
Pregnancy hormones- placental hormones that have subsequent effect on maternal endocrinology
Why are maternal adaptations to pregnancy important
To supply nutrients to fetus
To support amniotic fluid production
To clear fetal waste products
To meet fetal demands for glucose, amino acids + oxygen
Adapt in preparation for labour- protect mother from cardiovascular insult
Adaptations are in excess of fetal requirement
What are the pregnancy hormones
hCG, progestins, oestrogens, human placental lactogen, placental coricotropin releasing hormone, relaxin, oxytocin, prolactin
What is hCG
Produced by syncytiotrophoblast
Rises in first trimester then declines
Signals presence of blastocyst to mother
Maintains corpus luteum
What are progestins
Produced by corpus luteum then placenta Increase until just before labour Cause smooth muscle relaxation Inhibit oxytocin receptor expression Promote glucose deposition in fat stores Raises body temperature
What are oestrogens
Produced by corpus luteum then placenta Increase until just before labour Breast and nipple growth Uterine blood flow Myometrial growth Promote cardiovascular changes Water retention Alter carbohydrate metabolism Increase oxytocin receptors
What is human placental lactogen
Also known as somatomammotropin
Increases throughout pregnancy proportional to size of placenta
Converts mammary gland into milk-secreting tissue
Mobilises glucose from fat reserves to promote lipolysis
Reduces inuslin sensitivity
What is placental corticotropin releasing hormone
Produced by placenta
Increases throughout pregnancy
Timing of parturition
Interacts with fetal + maternal HPA systems
What is relaxin
Produced by corpus luteum, decidua + placenta
Facilitates remodelling of connective tissue of reproductive tract in preparation for labour
What is oxytocin
Produced by posterior pituitary and placenta Acts on uterus and breasts Contraction of smooth muscle Prostaglandin production Milk ejection reflex
What is prolactin
Produced in anterior pituitary
Milk production but only when oestrogen and progesterone have declined postpartum
Increases throughout pregnancy
How does the uterus adapt to pregancy
Mass increases 10-20x
Volume increase from 10ml to 5000ml
Composition: smooth muscle hyperplasia + hypertrophy then stretch effect
Increased supportive fibrous tissue
Orientation- straightens and dextrorotates
Immunology- uNK cells appear
How does the cervix adapt to pregnancy
Increased vascularity and oedema
Softening due to oestrogen and progesterone
Increased cervical glands, production of mucous plug
Hyperplasia of endovervical epithelium
How does the vagina adapt to pregnancy
Venous congestion
Oestrogen causes increased glycogen deposition which increases lactic acid which is protective
How does the breast adapt to pregnancy
Lactiferous ducts + alveoli proliferate due to oestrogen + progesterone Breast + nipple size increase Skin pigmentation changes Colostrum produced from 16 weeks Lactation
What are the cardiovascular changes during pregnancy
Heart rate increases 20% Stroke volume increases Cardiac output increases by 30-50% Total peripheral resistance decreases Blood pressure decreases Plasma volume increases 30-50%
What thoracic changes occur during pregnancy
Diaphragm elevated 4cm
Heart displaced up, left, apex moved laterally
Increased pulmonary blood flow
Increased ventricular muscle mass
Increased size of left ventricle + atrium
What problems does increased demands on overstretched system cause
Valve disease Pulmonary hypertension Connective tissue diseases Cardiomyopathies Ischaemic heart disease
What is aortocaval compression syndrome
From 20 weeks gravid uterus big enough to compress abdominal aorta + inferior vena cava
Supine position causes 30-50% reduction in cardiac output
Asymptomatic or cause hypertension
Reduces uteroplacental perfusion causing fetal distress, IUGR, stillbirth
Describe uterine blood flow during pregnancy
10% of cardiac output at term
500-800ml/min
Increased venous return, increased cardiac output
What are the mechanisms for changes in the respiratory system
Increased oxygen consumption Increased carbon dioxide production Increased tidal volume Increased ventilation Decreased partial pressure of CO2
What are the mechanical changes in the respiratory system
Uterus expands, lower ribs flare, ligaments relax.
Diameter of chest increases due to increase in subcostal angle
Diaphragm raised
Chest wall compliance decreases
What are the respiratory adaptations to pregnancy
Tidal vol increased 3-40% Total lung capacity decreased 5% Vital capacity no change Inspiratory capacity increased 15% Expiratory reserve volume decreased 25% Residual volume decreased 15% Functional residual capacity decreased 20% Respiratory rate no change
What is the relevance of respiratory changes
Maternal pCO2 reduced compared to fetal pCO2, facilitates gas exchange- also affects acid base chemistry
Physiological breathlessness of pregnancy
Relevant to anaesthetists
What are the haematological adaptations to pregnancy
Blood vol increases 45% White cell count increased T + B lymphocyte counts stable but decreased function- increased susceptibility to infection Platelet count unchanged Dilutional anaemia Hypercoagulable
What is dilutional anaemia of pregnancy
Increased red blood cell number and size Decreased haemoglobin Increased iron requirements Decreased haematocrit Occurs as plasma volume increase is greater than red cell increase
What is the hypercoagulable state in pregnancy
Procoagulatory clotting factors increase- 7, 8, 10
Inhibitory clotting factors decrease- antithrombin 3
Highest risk for thromboembolism in postnatal period
What are the structural renal adaptations to pregnancy
Increased blood flow
Increase 1cm length
Increased progesterone increases size of collecting system
Decreased tone, uterine can back up
Compression of ureter from gravid uterus causes physiological hydronephrosis
Overall effect- mild obstruction/urinary stasis
What are the functional adaptations to pregnancy
Increased renal flow 35-60%
Increased glomerular filtration rate 40-50%
Glycosuria common
Resistance to angiotensin II
RAAS generally activated
Increase in extracellular water + sodium/water retention
What are the gastrointestinal adaptations to pregnancy
Progesterone causes relaxed lower oesophageal sphincter, decreased gastric/intestinal motility
Increases gut transit time- enhanced nutrient uptake but increased constipation
Gall bladder increases in size but empties slower
