pregnancy: anatomic, physiologic and metabolic changes in pregnancy · 2020. 4. 24. ·...

Pregnancy: Anatomic, physiologic and metabolic

changes in pregnancy

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Physiology of pregnancy

• Pregnancy is the fertilization and development of one or more offspring, known as embryo or foetus, in a woman’s uterus.

• Following fertilization of the ovum, the first sign of pregnancy is amenorrhoea (cessation of menstruation).

• As pregnancy progresses, the uterus grows, its muscle fibreslengthening and thickening, and weight increases from 50g to1000g at term.

• Coordinated contraction of the uterus may be felt by the woman from about 20 weeks of pregnancy (Braxton hicks contraction). These contractions assist in blood flow through the placenta site, and in development of lower uterine segment.

PST 425 - Physiotherapy in Women's Health and nutritional Disorders

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• Pregnancy is governed and controlled by hormones which affect various systems.

• Progesterone decreases smooth muscle tone, initiates sensitivity to CO2 in the respiratory centre, and causes an increase in maternal temperature, breast development, and storage of fats deposits for milk production.

• Oestrogen influences uterine and breast growth and development, prepares prime receptor sites for relaxin (e.g. pelvic joints), and causes increased water retention.


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• In target areas relaxin replaces collagen with a modified form which greater pliability and extensibility. In has softening effect on connective tissue (pelvic floor and abdominal fascia, increasing extensibility up to 28 weeks of gestation

• Pregnancy lasts on average 40 weeks and is divided into three trimesters (periods of approximately 3 months). During this time many changes occur in the body owing to the growth of the foetus, the changes effected by the hormones, weight gain and subsequent postural alterations.


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Anatomical changes in Pregnancy

Skeletal system

Bones

• Volume of Calcium in the bones is decreases

• Acromegaloid changes in the second half (increasing level of IGH and STH) (fingers, hands)

Joints

• The sacroiliac synchondroses and symphysis pubis are widened and rendered movable (beginning about the 10th and 12th week of gestation through the work of relaxin).


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Anatomical changes

Skin-changes:

• Pigmentation of the skin in different areas (lineanigra)

• Chloasma(mask of pregnancy) may persist for many months after delivery on the face

• Palmar erythema (Oestrogen)


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Anatomical changes

Uterus

• Size:5-6 times increase (from 7 by 5 by 3 cm to 35 by 25 by 22 cm)

• Weight: 20-fold increase (50 → 1000 gramm)

• Capacity:1000-fold increase (4 → 4000 ml)

• Blood flow: 10-fold increase (50 → 500 ml/min)


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Changes in uterus


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Anatomical changes during pregnancy

• Connective tissue changes - Altered levels of relaxin, oestrogen and progesterone during pregnancy result in a change to collagen metabolism, and increased connective tissue pliability and extensibility.

• Ligamentous tissues are predisposed to laxity with resultant reduced passive joint stability. The symphysis pubis and sacroiliac joints are particularly affected to allow for passage of the baby.

• The ligamentous laxity may continue for 6 months postpartum. Pelvic joint loosening begins around 10 weeks with maximum loosening near term.


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• Musculoskeletal changes - During pregnancy there is stretching to the pelvic floor, and trauma during labourand vaginal delivery. There is an association between pelvic floor muscle dysfunction and pregnancy –related lumbopelvic pain.

• The change in the uterus size, leads to the change in centre of gravity, leads to an increased strain on the back muscles.


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• Hyperlordosis is seen resulting in progressive lumbar lordosis and rotation of the pelvis on the femur. This causes an increase in the anterior flexion of the cervical spine (a hunchback appearance) and adduction of the shoulders (rounding of the shoulder).


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Anatomical Changes

• There is also an increase in the laxity of ligaments throughout the body, causing a decreased stability of the joints.

• In the third trimester there is increased water retention, which may result in a varying degree of oedema of ankles and feet in most women, reducing joint range.


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Physiological changes during pregnancy

• Physiological changes occur in pregnancy to nurture the developing foetus and prepare the mother for labour and delivery. Some of these changes influence normal biochemical values while others may mimic symptoms of medical disease.

• Considerable changes occur in the woman’s body as the pregnancy progresses. Physiological and anatomical alterations develop in many organ systems during the course of pregnancy and delivery.

• Early changes are due, in part, to the metabolic demands brought on by the foetus, placenta and uterus and, in part, to the increasing levels of pregnancy hormones, particularly those of progesterone and oestrogen.


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Cardiovascular system

• Changes in the cardiovascular system in pregnancy are profound and begin early in pregnancy, such that by eight weeks’ gestation, the cardiac output has already increased by 20%.

• There are changes with the circulatory system apparent at rest during pregnancy: increase in blood volume, cardiac output, heart rate, and stroke volume, as well as a decrease in arterial blood pressure


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• Blood volume and pressure during pregnancy - The maternal blood volume shortly before term is about 30% above the normal. The cause of the increased volume is likely due to aldosterone and oestrogen, which are greatly increased in pregnancy and to increased fluid retention by the kidneys.

• Plasma increase is greater than red blood cell increases, leading to “physiological anaemia” of pregnancy, which is not a true anaemiabut is representative of the greater increase in plasma volume.


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• Peripheral vascular resistance decreases • progesterone decreases vascular smooth muscle tone

• Oestrogen causes vasodilation through nitric oxide

• Placenta releases prostacyclin (vasodilator)

• Consequently blood volume, cardiac output and GFR increase

• Blood pressure, plasma creatinine and urea should decrease in 1st

trimester.


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• Blood pressure decreases early in the first trimester. There is slight decrease of systolic pressure and a greater decrease of diastolic pressure.

• Blood pressure reaches its lowest level approximately midway through pregnancy, then rises gradually from mid-pregnancy to reach the pre-pregnant level approximately 6 weeks after delivery.

• Cardiac output increases 30% to 60% during pregnancy and is most significantly increased when a woman is in the left side-lying position, in which the uterus places the least pressure on the aorta.


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• The increased blood volume serves two purposes. • First, it facilitates maternal and foetal exchanges of respiratory gases,

nutrients and metabolites.

• Second, it reduces the impact of maternal blood loss at delivery.

• Venous pressure in the lower extremities increases during standing as a result of increased uterine size and increased venous distensibility..


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Supine hypotension related to Venal cava syndrome


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Pressure in the inferior vena cava rises in late pregnancy especially in the supine position, because of compression by the uterus just below the diaphragm



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Increase

Total blood volume

Red blood cell volume

Renal Erythropoetic

factor

Total Heamoglobin

Cardiac output

Heart rate

Glomerular filtration rate


• Blood pressure (BP):

• Arterial BP does not increase in normal pregnancy!

• Vena cava syndrome (late in pregnancy)!

• Capillary permeability remains unchanged


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• Respiratory system

• Because of the increased basal metabolic rate of a pregnant woman and because of her greater size, the total amount of oxygen used by the mother shortly before birth of the baby is about 20 percent above normal, and a commensurate amount of carbon dioxide is formed.

• Oedema and tissue congestion of the upper respiratory tract begin early in pregnancy because of hormonal changes.

• Dyspnoea is present with exercise as early as 20 weeks into the pregnancy.


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• Respiration - The vital capacity remains normal. There is an increase in tidal volume (almost 50%), which causes an increase in minute ventilation throughout (21% and 50% in the second and third trimesters respectively).

• There is 15% to 20% increase in oxygen consumption; a natural state of hyperventilation exist throughout pregnancy to meet the oxygen demands of pregnancy. The work of breathing increases because of hyperventilation


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• The enlarged uterus occurring later in gestation increases the pressure on the diaphragm causing an increase in resting oxygen requirements and an increase in the work required for breathing .

• This happens because the diaphragm is a key muscle responsible for proper respiration, it helps to inflate the lungs; with extra pressure from the uterus it is harder for the diaphragm to contract, using more energy to bring in the same amount of air. This means there is a decreased amount of oxygen available for performance during aerobic exercise.


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Respiratory ChangesRespiratory Changes

Respiratory capacity Respiratory capacity

increasesincreases

Shortness of breathShortness of breath

Pulmonary reserve Pulmonary reserve

decreasesdecreases

Increased risk of Increased risk of

muscle sorenessmuscle soreness

Tendency to Tendency to

hyperventilatehyperventilate

RESULT RESULT adjust the intensity level and duration of exerciseadjust the intensity level and duration of exercise


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• Vital capacity remains unchanged

• Hyperventilation

• Tidal volume

• Carbon dioxide level of alveolar air

• Carbon dioxide level of maternal circulation

• CO2 level of foetal circulation


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• Urinary System function –

• The rate of urine formation by a pregnant woman is usually slightly increased because of increased fluid intake and increased load or excretory products.

• The glomerular filtration rate increases as much as 50 percent during pregnancy, which tends to increase the rate of water and electrolyte excretion in the urine. With all these effects, the normal pregnant woman ordinarily accumulates only about 6 pounds of extra water and salt.


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• The bladder is pulled up into the abdomen as the uterus enlarges.

• Pressure of the uterus on the bladder, traction at the vesicle neck and hyperaemia of the trigone cause increase frequency of urination

• Vascularity of the bladder increases

• Varicosity and haemorrhage from these areas

• Decrease in bladder tone

• Progressive increase in capacity up to 1300 to 1500 ml during pregnancy (from 300-400ml)

• Over-distension of the bladder


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Physiological changes during pregnancy - GIT

• Alteration in the normal alkaline pH of the saliva toward acid side!

• Quantity of saliva increases (hyperptyalism)

• Gums tend to bleed easily (hormonal effect) (gingivitis tends to disappear after delivery)

• Gastric acidity is usually reduced

• Gastric motility is reduced

• Nausea and vomiting in early pregnancy


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Metabolic changes during pregnancy

• Metabolism during pregnancy - During pregnancy, basal metabolic rate and heat production increase. In pregnant women, normal fasting blood glucose levels are lower than in non pregnant women. With pregnancy comes an increase in the metabolic rate resulting in greater metabolic rate.

• The greater metabolic rate also calls for a higher need for energy for energy or higher food consumption. The foetus metabolic rate generates additional heat.

• The physiologic changes (increased skin blood flow) occurring during pregnancy help to reduce maternal body temperature. Greater amount of energy than normal must be expended for muscle activity.


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• Progesterone increase body temperature, therefore metabolic rate• So oxygen consumption increases

• Progesterone increases sensitivity of central chemosensors to CO2

• Also physical changes in space available means that more of the inspiratory reserve volume is used.


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Proteins:

• Positive nitrogen balance increases progressively through the third trimester when foetal requirements are greatest.

• Nitrogen accumulates during pregnancy.

• Diet very important in case of hypoproteinaemia!


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Carbohydrates:

• Renal threshold for glucose may be reduced from non-pregnant levels (150-200 mg/dl to 100-150 mg/dl)

• Secretion of insulin is increased

• Resistance to insulin and destruction of insulin also increased


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Fats:

• Increase in maternal use of fat stores

• Increase in insulin resistance

• Oestrogen increase production of the alpha globulins (lipoproteins)

• Lipoproteins increased during pregnancy

• Neutral fats are doubled

• Ketonuria occurs more readily in pregnant


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• Postural and balance changes - The overall equilibrium of the spine and pelvis alters as pregnancy progresses. With weight gain, increased blood volume and ventral growth of the foetus, the centreof gravity no longer falls over the feet and the woman needs to lean back to gain equilibrium, resulting in disorganization of spinal nerves.

• During the conception period the uterus can expand up to 1000 times, causing an anterior orientation of the uterus. The growth of the uterus causes the body to respond with a shift in the centre of gravity. The centre of gravity is shifted back over the pelvis in response, preventing women from falling, the body’s safety mechanism.


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• Additionally the centre of gravity usually shifts higher, with this there is an increased strain on the muscles and ligaments supporting the vertebral column.

• The lumbar and cervical lordoses increases to compensate for the shift in the centre of gravity and the knees are hyperextended.

• The shoulder girdle and upper back become rounded with scapular protraction and upper extremity internal rotation because of breast enlargement; this postural tendency persists with postpartum positioning for infant care.


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• Tightness of the pectoralis muscles and weakness of the scapular stabilizers may be pre-existing to or perpetuated by the pregnancy postural change. The suboccipital muscles respond in an effort to maintain appropriate eye level (optical righting reflex), and moderate forward head posture along with the change in shoulder alignment.


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Pregnancy induced pathologies

Pregnancy induced pathology and interventions

• The combined influence of hormones, weight gain, and postural changes of contributes to a variety of impairments that can be addressed with physical therapy.

Diastatis Recti

• Diastasis recti is separation of the rectus abdominis in the midline of linea alba.

• may occur in pregnancy as a result of hormonal effects on the connective tissue and the biomechanical changes of pregnancy

• It may also develop during labour, especially with excessive breath – holding during the second stage.

• Interventions include exercises for correction of diastasis recti. Exercises include head lift and head lift with pelvic tilt exercise.

Postural back pain

• Back pain commonly occurs because of postural changes of pregnancy, increased ligamentous laxity, and decreased abdominal muscle function.

• Back pain is reported by 50% to 70% of pregnant women at some point during pregnancy.

Postural back pain

• Low back pain symptoms can be treated effectively with:• traditional low back exercises, • proper body mechanics, • posture instructions, • improvement in work techniques • superficial modality application.

Sacroiliac/Pelvic Girdle pain

• Sacroiliac pain is localized to the posterior pelvis and is described as stabbing deep into the buttocks distal and lateral to L5/S1.

• Symptoms include pain with • prolonged sitting, • standing or walking, • climbing stairs, • turning in bed

Sacroiliac/Pelvic Girdle pain

• Interventions include modification or elimination of activities that further aggravate sensitive tissue, stabilization exercises, and the use of belts and corsets to provide external support to the pelvis.

Varicose Veins

• Varicose veins are aggravated in pregnancy by • increased uterine weight, • venous stasis in the legs, • increased venous distensibility.

• They can occur in the • lower extremities, • the rectum, or • the vulva.

Varicose Veins

Intervention

• Elastic support stockings should be worn to provide an external pressure gradient against the distended veins,

• Elevation of the lower extremities as often as possible.

• Vulvar varicosities may benefit from use of a perineal belt that provides counter- pressure and support to the tissues.

Joint laxity

• All joint structures are at increased risk of injury during pregnancy and during the immediate postpartum period.

• The tensile quality of the ligamentous support is decreased and therefore injury can occur if women are not educated regarding joint protection.

Joint laxity

• Intervention is in the form of exercise modification.

• The woman should know about safe exercise in the child bearing year, including modification of exercises to decrease excessive joint stress.

• Non – weight bearing or less stressful aerobic activities such as swimming, walking can be performed by women who are relatively sedentary before pregnancy.

Nerve compression syndromes

• Impairments from conditions such as thoracic outlet syndrome or carpal tunnel syndrome may be caused by one or more of the following in pregnancy:• postural changes in the neck and upper quarter, • fluid retention, • hormonal changes, or • circulatory compromise.

Nerve compression syndromes

• Nerve compression syndromes may also occur in the lower extremities because of the weight of the foetus, fluid retention, hormonal changes, or circulatory compromise.

• Interventions include • postural correction exercises, • manual techniques, • ergonomic assessment and modalities. • Splints may be used in the treatment of carpal tunnel

syndrome.

pregnancy: anatomic, physiologic and metabolic changes in pregnancy · 2020. 4. 24. ·...

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