Physiologic changes of pregnancy

Prof. Aziza Tosson

AIMS

TO GAIN AN UNDERSTANDING OF THE PHYSIOLOGICAL CHANGES THAT OCCUR DURING PREGNANCY

LEARNING OUTCOMES IDENTIFY THE CHANGES THAT TAKE PLACE

WITHIN THE UTERUS AND BODY SYSTEMS DURING PREGNANCY

CONSIDER THE EFFECT THESE CHANGES HAVE ON THE WOMAN

EXPLORE THE ROLE OF THE MIDWIFE WHEN GIVING ADVISE TO THESE WOMEN

ObjectivesSymptoms and physical findings of each

organ systemPhysiologic versus pathologic changesDiagnostic tests and interpretations

during physiological changes

UNDERSTANDING NEEDED TO EXPLAIN THE PHYSIOLOGICAL

CHANGES THAT TAKE PLACE TO THE WOMAN

TO UNDERSTAND THE MINOR DISORDERS OF PREGNANCY

RECOGNISE PATHOLOGICAL CHANGES IN ORDER TO REFER APPROPRIATELY

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Anatomical ChangesAnatomical Changes

PelvisPelvis

Pelvic Floor MusclesPelvic Floor Muscles

UterusUterus

Uterine LigamentsUterine Ligaments

CervixCervix

PlacentaPlacenta

Amniotic FluidAmniotic Fluid

PelvisPelvis

Pelvic Floor MusclesPelvic Floor Muscles

NormalNormal DiastasisDiastasis

Abdominal Abdominal DiastasisDiastasis

Physiological ChangesCirculatory

Thermoregulation

Metabolic

Respiratory

Digestive

Urinary

Skin

Breasts

Biomechanical

DEFINITIONTHE CHANGES THAT TAKE PLACE IN

THE MATERNAL ORGAN SYSTEM IN

RESPONSE TO PREGNANCY.

TO ACCOMADATE THE PREGNANCY

AND TO PREPARE THE WOMAN FOR

LABOUR

Organ systemsCardiovascular systemPulmonary systemGenital tractUrinary systemEndocrine systemGastrointestinal TractSkin

CHANGES ARE DUE TOALTERATIONS IN

HORMONAL PRODUCTION

CIRCULATION

METABOLISM

HORMONES

OESTROGEN

Produced in corpus luteum

Produced by placenta after 12 weeks

Responsible for growth particularly of uterus and breasts

progesterone Produced in corpus luteum and then the

placenta

Relaxes smooth muscle

Inhibits uterine contractions until uterus is prepared for labour

Regulates storage of body fat

Human chorionic gonadotrophicSecreted from trophoblast of the

developing embryo

Maintains corpus luteum until placenta takes over

Used in tests to confirm pregnancy

Human placental lactogenAlters maternal metabolism

Diverts glucose to fetus

Mobilises free fatty acids from maternal stores

RELAXIN

Released by corpus luteum then the Placenta

Softens pelvic ligaments

Reduces myometrial tone

Changes to Body SystemChanges to Body System

First TrimesterFirst Trimester Baby begins to growBaby begins to grow

Increased urinationIncreased urination

Changes with skin and Changes with skin and hairhair

Thickening waistlineThickening waistline

Nausea/fatigueNausea/fatigue

Second TrimesterSecond Trimester BabyBaby’’s weight increasess weight increases

Energy level improvesEnergy level improves

HeartburnHeartburn

Leg crampsLeg cramps

Pelvis relaxes causing SI Pelvis relaxes causing SI discomfortdiscomfort

Third TrimesterThird Trimester Baby has more rapid Baby has more rapid

growth & weight gaingrowth & weight gain

BackachesBackaches

Swelling of the hands, Swelling of the hands, legs, and feetlegs, and feet

BreathlessnessBreathlessness

More frequent More frequent urinationurination

Maternal changes - anatomical and physiological

Cardiovascular changes increase in SV increase in cardiac output increase in HR at given work load increase in blood volume (mostly during latter half

of pregnancy) Uterus may compress large blood vessels reducing

venous returnTotal Body water

Circulatory System

Cardiovascular Changes

Blood volume

Cardiac (heart) output

Stroke volume

End diastolic volume

Resting pulse

% of blood plasma

Hematocrit

Blood pressure

Blood supply to uterus

Cardiac reserve

Vascular resistance

DECREASEDECREASEINCREASEINCREASE

Wajed Hatamleh RN, MSN, PhD.Wajed Hatamleh RN, MSN, PhD.

Cardiovascular SystemCardiovascular System Heart shifts up and to the leftHeart shifts up and to the left

Hemoglobin stays the same (12-16 g/dL) initiallyHemoglobin stays the same (12-16 g/dL) initially May drop down to 10 g/dL and still be normal May drop down to 10 g/dL and still be normal

physiologic anemia.physiologic anemia. Normal pregnancy Hgb is 10-14 g/dL later in Normal pregnancy Hgb is 10-14 g/dL later in

pregnancypregnancy Decreased Hct (38-47%)Decreased Hct (38-47%)

Normal pregnancy Hct is 32-42 later in pregnancyNormal pregnancy Hct is 32-42 later in pregnancy Pulse rate may increase 10-15 beats.Pulse rate may increase 10-15 beats. Weight of uterus can cause supine hypotensive Weight of uterus can cause supine hypotensive

syndrome.syndrome.

Supine hypotension related to Supine hypotension related to Venal cava syndromeVenal cava syndrome

This leads to dizziness, air hunger, nausea

Total body water Increases 6-8 L Increases by 40 %Normal body water

2/3 intracellular 1/3 extracellular

¾ interstitial ¼ intravasular

2/3 increase is extravascular

Physiologic anemia of pregnancy Physiologic intravascular change Plasma volume increases 50-70 %

Beginning by the 6th wk RBC mass increases 20-35 %

Beginning by the 12th wk Disproportionate increase in plasma volume

over RBC volume----Hemodilution Despite erythrocyte production there is a

physiologic fall in the hemoglobin and hematocrit readings

Iron deficiency anemia With erythropoiesis of pregnancy, iron

requirements increase. Because large amounts of iron may not be

available from body stores and may not be in the diet

Supplementation is recommended to prevent iron deficiency anemia

At term, Hemoglobin less than 10.0 is usually due to iron deficiency anemia rather than the hemodilution of pregnancy

Normal Iron Requirements Total body iron content average in normal adult

females is 2gm Iron requirement for normal pregnancy is 1 gm

200 mg is excreted 300 mg is transferred to fetus 500 mg is need for mom

Total volume of RBC inc is 450 ml 1 ml of RBCs contains 1.1 mg of iron 450 ml X 1.1 mg/ml = 500 mg

Daily average is 6-7 mg/day Small intervals between pregnancies are most

concerning

Respiratory systemMechanical

diaphragmConsumption

Increase in needed oxygenStimulation

Progesterone stimulation

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

Physiologic changes - Physiologic changes -

RESPIRATORY SYSTEMRESPIRATORY SYSTEM

increase respiratory rateincrease respiratory rate increased oxygen consumptionincreased oxygen consumptioncommon are nasal stuffiness, common are nasal stuffiness,

nosebleeds due to nosebleeds due to Increased Increased vascular swelling to nosevascular swelling to nose

Respiratory Consumption

O2 consumption Increases 15-20 % 50 % of this increase is required by the uterus Despite increase in oxygen requirements, with the

increase in Cardiac Output and increase in alveolar ventilation oxygen consumption exceeds the requirements.

Therefore, arteriovenous oxygen difference falls and arterial PCO2 falls.

Physiologic changes -Physiologic changes - GASTROINTESTINALGASTROINTESTINAL

Digestive system slow due to progesteroneDigestive system slow due to progesteroneNausea and vomitingPtyalism: increase salivationHeartburn Hemorrhoids Prolonged gallbladder emptying time may lead Prolonged gallbladder emptying time may lead

to gall stonesto gall stones Bile salt buildup may lead to itching.Bile salt buildup may lead to itching.

Gastrointestinal Tract Displacement of the stomach and intestines Appendix can be displaced to reach the right

flank Gastric emptying and intestinal transit times are

delayed secondary to hormonal and mechanical factors

Pyrosis is common due to the reflux of secretions

Vascular swelling of the gums Hemorrhoids due to elevated pressure in veins

Digestive ChangesDigestive Changes

Digestive system slows Digestive system slows

Intestines are pushed up Intestines are pushed up and to the sides and to the sides

Smooth muscle of the Smooth muscle of the stomach relaxes and can stomach relaxes and can cause heartburncause heartburn

Constipation and hemorrhoids are Constipation and hemorrhoids are common during pregnancycommon during pregnancy

Morning sicknessMorning sickness

Physiologic changes -Physiologic changes - METABOLISMMETABOLISM

BMR increases by 20-25 % during pregnancy

Recommended weight gain – 25-35 lbOverweight – 15-25 lbUnderweight – 25-35 lb

Need for increased iron, calcium, fat, and protein

Metabolic Changes

Insulin level Carbohydrate utilization during exercise as

weight increasesEstrogen Progesterone RelaxinCaloric requirements by ~ 300 calories/dayProtein and fluid requirements

INCREASES IN:INCREASES IN:

Genital Tract Increased vascularity and hyperemia

Vagina Perineum Vulva

Increased secretions Characteristic violet color of the vagina

Chadwick’s sign Increased length to the vaginal wall Hypertrophy of the papillae of the vaginal

mucosa

Physiologic changes in Physiologic changes in pregnancy - Reproductive systempregnancy - Reproductive system

Uterus – Uterus – Enlarges : esp fundal area thickens, then Enlarges : esp fundal area thickens, then

thins later in pregthins later in preg Umbilicus by 20 weeksUmbilicus by 20 weeks Xyphoid by 36 weeks fundus, Braxton-Xyphoid by 36 weeks fundus, Braxton-

Hicks irregular contractions after 4 Hicks irregular contractions after 4 monthsmonths

Cervix – mucous plug, Goodell’s sign, Cervix – mucous plug, Goodell’s sign, Chadwick’s signChadwick’s sign

Ovaries –after 11 weeks, the plac prod Ovaries –after 11 weeks, the plac prod progesterone and estrogenprogesterone and estrogen

Changes in the cervixLength remains the same Increase in widthSoftening after third month due to

oestrogen Increased vascularity Increased cervical mucosa Increased glandular function

changes in sizeuterus grows to 30x23x20 at termweight increases to 900gms

hypertrophy.. Oestrogen causes cells to increase until 20 weeks gestation Hyperplasia:- number of cells increase under the influence of oestrogen.

After 20 weeks gestation

Uterine muscle tissue stretches to allow fetus to grow

Progesterone relaxes the smooth muscles enabling it to stretch

Relative Uterus Size During Pregnancy

Figure 28.15

Changes in the shape of the uterus

Isthmus elongates during the 1st 10 weeks like a stalk

From 7mm to 2.5cms at 10 weeks

Later becomes the lower segment with the globular uterus sitting on top

ORGANISATION OF MUSCLE FIBRES

Inner circular layer Surrounds cornua, lower uterine segment and

cervix

Middle layer Oblique, crisscross arrangement involved in

contractions to expel fetus

Outer longitudinal layer Contracts and retracts thickening the upper

segment

BY 12 WEEKSUterus is upright and leans slightly to the

rightNo longer a pelvic organUterus may be palpable above the pubic

boneFetus now occupies most of the uterine

cavityPlacenta now developed

2ND TRIMESTA Development of the upper and lower

uterine segmentUpper segment, thicker containing oblique

musclesLower segment formed from the isthmus

contains circular and longitudinal musclesUterus is pear shaped againBraxton Hicks contractions

3rd TRIMESTA

Lower segment formed from isthmus and contains longitudinal fibres

Upper segment thick and contains oblique muscle fibres

By 36 weeks lower segment measures 8-10cms

EngagementBy 38 weeks the cervix is taken up into

the lower segment

BLOOD CHANGES Increase in oestrogen:

new blood vessels formed

growth of existing ones

Therefore an increase in blood volume.

BLOOD SUPPLY TO UTERUS

Blood supply pre pregnancy = 10mls/min

At 40weeks 800 – 900mls/min

20% of cardiac output goes to uterus

Blood volume: from 5 litres to 7.5

total volume up by 40-50%

Red cell mass: rises constantly throughout

pregancy

Up by 20% by end of

pregnancy

PLASMA VOLUME

Increases from 10th week of pregnancy

variable related to parity, fetal weight and number

Reaches maximum level approx 50% above non-pregnant levels at 32-34 weeks then maintained

50% rise in plasma volume

20% rise in red cell mass

Heamodilution: Physiological anaemiaMost apparent at 32-34 weeks

RENAL SYSTEMDILATION OF THE RENAL VESSELSDUE THE EFFECTS OF

PROGESTERONE

INCREASED RENAL BLOOD FLOWGFR INCREASES BY 60% IN EARLY

PREGNANCYSIZE OF PORES INCREASED

Urinary Changes Kidneys grow and filter more

blood as the blood volume increases

Become more susceptible to bladder and kidney infections

Bladder becomes compressed causing frequent urination and incontinence

Wajed Hatamleh RN, MSN, PhD.Wajed Hatamleh RN, MSN, PhD.

Physiologic changes -Physiologic changes -

URINARY TRACTURINARY TRACT

Increased glomerular filtration rateIncreased glomerular filtration rateFrequencyFrequencyInfection : Infection : Smooth muscle of Smooth muscle of

bladder relaxes/stasisbladder relaxes/stasis

Endocrine Normal pregnancy physiology shows

“lower lows and higher highs” Postprandial hyperglycemia

To ensure sustained glucose levels for fetus Accelerated starvation

Early switch from glucose to lipids for fuels Insulin resistance promotes hyperglycemia

Resistance-Reduced peripheral uptake of glucose for a given dose of insulin

Mild fasting hypoglycemia occurs with elevated FFA, triglycerides,and cholesterol

WATER, WATER, WATER

Provide a ready source of water Encourage frequent water breaks

Hydration is a major concern Hydration is a major concern during maternal exercise.during maternal exercise.

Insulin resistanceAnti-insulin environment is aided by:placental lactogen

Like growth hormone Increases lipolysis and FFA Increases tissue resistance to insulin

Increased unbound cortisol Estrogen and Progesterone may also

exert some anti-insulin effects

Thyroid Estrogen stimulates Increase in TBG

Total T3 and T4 are increased However the active hormones remains unchanged

hCG stimulates thyroid TSH is reduced

Iodine deficient state Due to Increased renal clearance

To rule out pathologic changes Early in pregnancy TSH can be used Later free T4 is needed

LiverLiver morphology unchangedLab Tests similar to liver disease

Alkaline phosphatase doubles AST, ALT, GGT and bilirubin are slightly

lower Decreased plasma albumin

Gallbladder Impaired contractionHigh residual volumesPromotion of stasisStasis associated with increased

cholesterol saturation of pregnancy, supports predisposition of stones

Intrahepatic cholestasisRetained bile salts-pruritus gravidarum

Wajed Hatamleh RN, MSN, PhD.Wajed Hatamleh RN, MSN, PhD.

Physiologic changes -Physiologic changes -INTEGUMENTARY SYSTEMINTEGUMENTARY SYSTEMThese result from stretching of the skin and These result from stretching of the skin and

hormonal changeshormonal changesLinea nigra: pigmentation down middle line pigmentation down middle line

of abdof abdChloasma – “mask of pregnancy”Straie: stretch marks of abd, breasts, stretch marks of abd, breasts,

thighs and buttocksthighs and buttocksSweating

Skin changesChloasma or melasma gravidarumStriaeLinea nigra

Skin ChangesStretch marks

Dark pigmented line on there abdomen which is called Linea Nigra

Pigment changes on their face and neck

Small blood vessels in the face, neck and upper chest

MOST OF THESE RESOLVE AFTER PREGNANCY

Melasma

Melasma

MelasmaAlso known as the mask of pregnancyMore common in dark skin peopleMore pronounced in the summerFades a few months after deliveryRepeated pregnancy can intensifyCan occur in normal non-pregnant

women with harmless hormonal imbalances or women on OCPs or depo

Striae

StriaeReddish slightly depressedBreasts, thighs, and abdomen In future pregnancies they appear as

glistening, silver lines

Linea nigra

HyperpigmentationMelasma and linea nigraEstrogen and progesterone Some melanocyte stimulating effect

Breast Changes

Nipples become larger and darker

A thick yellowish fluid can be expressed from the nipple

Early in pregnancy, Early in pregnancy, tenderness and tightness tenderness and tightness is commonis common

After 8 weeks, breasts After 8 weeks, breasts grow and blood vessels grow and blood vessels often are visibleoften are visible

Wajed Hatamleh RN, MSN, PhD.Wajed Hatamleh RN, MSN, PhD.

MS systemMS system

Joint relaxationJoint relaxation Posture changesPosture changes -lordosis/center of -lordosis/center of

gravity gravity Back acheBack ache Diastasis recti: separation of rectus Diastasis recti: separation of rectus

abdominous abdominous Leg cramp due to calcium, and Leg cramp due to calcium, and

stretching stretching

Pelvic Floor Muscle Functions

Maintain alignment and support of internal organs

Control of urine flow

Sexual enhancement

Eliminate waste from rectum

Improve recovery from episiotomy

Uterus & Uterine Ligaments

UterusUterus

Broad Broad ligamentligament

Round Round ligamentligament

Biomechanical ChangesWeight distribution shifts

Joint movement

Balance of muscle strength

Spinal curves increase

Joint laxity becomes greater

More structural discomfort

Increased potential for nerve compression

Potential for InjuryNerve compression

syndromes

Low back discomforts or pelvic pain

Upper back fatigue

Lower extremity

Pelvic floor function

Postural Dynamics Increased curve of the waist

Top of pelvis tilts forward

More flexion in the hip joint

Increased hunching in the upper back and neck

Tailbone is pushed back

Muscles Affected Overstretching & weakening of gluteal muscles &

hamstrings Overstretching & weakening of abdominal

muscles & pelvic floor Overstretching & weakening of upper back

muscles Shortening and tightening of low back & hip

flexors muscles Shortening of upper back flexors & pectoral

muscles

Wajed Hatamleh RN, MSN, PhD.Wajed Hatamleh RN, MSN, PhD.

Neurological and sensoryNeurological and sensory

Decreased intraoccular pressureDecreased intraoccular pressure Corneal thickeningCorneal thickening Altered sense of smellAltered sense of smell Decreased attention spanDecreased attention span Problems with memoryProblems with memory Altered CNS physiology leading to Altered CNS physiology leading to

mood disturbance.mood disturbance.

Combat Effects of Gravity/ Hormones

Do pelvic tilts Alter the stance Shorten the jog stride Lower or eliminate the

step in aerobics Avoid rapid leg abduction Avoid breast stroke kick in

swimming Recognize tolerance for

activities will vary

Do pelvic floor exercises to prevent trauma

Emphasize strengthening & stretching exercises

Wear abdominal support/ sports bra when exercising for support

Changes to Body System First Trimester Baby begins to grow Increased urination Changes with skin and hair Thickening waistline Nausea/fatigue

Second Trimester Baby’s weight increases Energy level improves Heartburn Leg cramps Pelvis relaxes causing SI

discomfort

Third Trimester Baby has more rapid

growth & weight gain Backaches Swelling of the hands, legs,

and feet Breathlessness More frequent urination