H:\Physiological Changes In Pregnancy[2]

Physiological Changes in Pregnancy

Sandy Warner RNC – OB, MSN

Adaptations

• Nurses must understand the normal anatomical and physiological changes in pregnancy to recognize any deviation from normal.

• In addition to physical changes, there are also psychological changes that occur with pregnancy.

Body system alterations• Cardiovascular • Hematological• Respiratory• Genitourinary• Gastrointestinal• Immunological• Musculoskeletal• Endocrine

Cardiovascular

• Cardiovascular adaptation affects all organ systems.

• Cardiovascular anatomy and physiology changes to accommodate increasing maternal and fetal circulatory needs.

Heart

• Anatomic changes:

– Heart is enlarged, displaced upward and rotates to the left.

– PMI (point of maximal impulse) shifts to 4th

intercostal space and closer to the midclavicular line.

Heart sounds and rate:

• Audible splitting of S1 and S2; S 3 becomes audible.

• Benign systolic murmurs are common.

• Heart rate increases 15-20 beats as pregnancy progresses.

Cardiac Output

• Defined as the amount of blood pumped from the left ventricle into the aorta each minute.– (heart rate x stroke volume = CO)

• In pregnancy increased by 40% by 36-38 wks.

• Influenced by: • Blood volume• Stroke volume• Heart rate

TIME FRAME CARDIAC OUTPUT CHANGE

1st Trimester Increased 22% > pre-pregnancy values due to increased stroke volume

3rd Trimester Increased 30-50% > pre-pregnancy values due to increased heart rate and stroke

Labor Increased 12%-49% during 1st and 2nd stage due to shunting of blood from uterus to maternal circulation with ctxs and pushing

Blood Pressure

• Due to decreased systemic vascular resistance, blood pressure is lower at end

of 1st trimester and throughout 2nd, returning to baseline in 3rd trimester.

Also affected by renin-angiotensin-aldosterone system from kidneys.

Hematological Changes

• Increase in WBCs and RBCs.

• Increase blood volume for uterus, fetus and increased perfusion of other organs, especially kidneys.

• Increased plasma volume ratio to RBC volume leads to hemodilution.

Hematological changes cont.

• Hypercoagulation

• Decreased fibrinolytic activity

• Platelets remain normal or might decrease slightly

• Increased need for iron related to RBCs

Respiratory

• Anatomic changes:– Diaphragm elevation

– Chest expansion

– Capillary dilation early in pregnancy causes• Engorgement of entire tract from nares to bronchi• Voice changes

Respiratory

• Physiological changes:– Increased need for oxygen

– Improved oxygen delivery

– Hyperventilation

– Compensatory respiratory alkalosis

Genitourinary

• Kidneys – increase in size and GFR.

• Ureters – dilate and elongate, becoming compressed by uterus.

Bladder – tone decreases due to progesterone, becomes displaces as uterus grows.

Genitourinary

• Urine flow accumulates and slows.• Increased renal excretion of BUN,

creatinine and glucose.• Decreased serum BUN, creatinine and

glucose.• Decreased tubular reabsorption of

glucose.• Increased tubular reabsoption of sodium.

Genitourinary

• Uterus – rises out of pelvis during 1st trimester.

• Weight increases from 70 gms to 1100 gms.• Volume at term averages 5 L but may be as

much as 20 L.

Individual cells increase 100 fold in length by term,

allowing for contractions and involution.

Genitourinary

• Cervix:– Increases in mass and fluid content.– 85% connective tissue and 15% smooth

muscle.– Ripening occurs via softening and effacement

with the influence of hormones.

Gastrointestinal

• Mouth – changes in tastes, increase in saliva production, gums swell and bleed easier.

• Esophagus – decreased tone leads to reflux.

• Stomach – decreased tone and motility.• Intestines – smooth muscle relaxation and

decreased tone and motility - constipation

Gastrointestinal

• Esophagus, stomach and intestines move as uterus grows.

• Round ligament stretches as uterus expands.

• Gallbladder –decrease tone and motilitycombined with increased emptying time can

cause increased risk of gallstones.

Gastrointestinal

• Hyperemesis – common in first trimester.– Strong sense of smell.– Increased saliva production.– Can persist throughout pregnancy.

Immunological

• Placenta functions to help protect the fetus from infection with IgG.

• Decreased Tcell activity with pregnancy that increases susceptibility to viral infections.

• Immunity is enhanced by sleep/rest and decreased stress.

Musculoskeletal

• Abdominal muscles relax and pelvis tilts forward.

• Center of gravity shifts.• Joints relax – waddling.• Muscle aches from increasing weight of

uterus.• Posture change due to lumbodorsal curve

of spine.

Musculoskeletal

• Normal weight gain 25-35#.

• Slight weight loss in 1st trimester from

nausea and vomiting.

Average 1#/wk weight gain in 2nd and 3rd trimesters.

Endocrine

• Thyroid:• Function increases to meet metabolic and growth

needs.

• Parathyroid:• Helps regulate calcium, phosphorus, Vit. D and

magnesium concentration.• Increases in pregnancy to help skeletal growth.