OBJECTIVE Pregnancy causes physiologic changes in all

maternal organ systems; most return to normal after delivery.

In general, the changes are more dramatic in multifetal than in single pregnancies.

Major adaptations in maternal anatomy, physiology, and metabolism are required for successful pregnancy.

Nearly every organ system is affected. Understanding these changes helps to

distinguish normal physiology from pathological disease states.

BODY WATER METABOLISM

Condition of chronic water overload Active Na and water retention

1. Changes in osmoregulation

2. Renin-angiotensin system Body water increase 6.5L 8.5L

1. 1500 cc increase in blood vol

2. RBC increase ~400cc Elevation of maternal CO

OSMOREGULATION

Na retention increases 900 mEq but serum Na decreases 3-4 mmol/l

Plasma osmolality decreases 10 mOsm/kg Enhanced tubular reabsorption of Na

secondary to aldosterone,estrogen and deoxycorticosterone.

Increased GFR and Atrial Natriuretic Peptide favor Na excretion

CARDIOVASCULAR CHANGESHeart Displaced to the left and upward Apex is moved laterally Apparent cardiomegaly on chest x-ray Increase in left ventricular end- diastolic dimension Increase in left ventricular wall mass c/w mild

hypertrophy Increase in preload with increase capacitance of the systemic and pulmonary vascular resistances to prevent rise in CVP or wedge pressure.

Grade II-III systolic flow murmurs at left lower sternal border

RESPIRATORY CHANGESUpper Respiratory Tract Hyperemia and edema induced by estrogen Nasal stuffiness and epistaxis

Mechanical changes (earlier than mechanical pressure of rising uterus

Chest circumference expands 5-7 cm Subcostal angle increases from 68 to 103 degrees Transverse diameter increases 2cm Level of diaphragm rises 4cm but excursion is not

impeded Respiratory muscle function is not affected by

pregnancy

LUNG VOLUME AND PULMONARY FUNCTION

Elevation of the diaphragm decreases the volume of the lungs in the resting state, reducing TLC by 5% and

FRC by 20% FRC mainly decreased by RV Vital capacity does not change Spirometry is not changed in pregnancy

FEV1 is unchanged

Peak flow is unchanged

RESPIRATORY CHANGES

Chronic hyperventilation Progesterone induced Minute volume is increased Tidal volume is increased Respiratory rate is unchanged Increased early in the first trimester

HEMATOLOGIC CHANGES

40-50% increase in blood volume beginning at 6 weeks and plateaus at 30 weeks

Both plasma volume and cell mass increase Physiologic anemia of pregnancy nadiring at

30 weeks Increase in erythropoietin and reticulocyte

count

IRON METABOLISM Absorption in the duodenum in the divalent state Trivalent food source must be converted by ferric

reductase to divalent form Fe enterocytes bound transferrin

transported to liver, spleen, muscle and bone marrow incorporated into hemoglobin, myoglobin, ferritin or hemosiderin

1000mg iron requirement, about 3.5 mg/dL of Fe Requirements increase in third trimester Fetus receives Fe through active transport

FE SUPPLEMENTATION

Fe supplementation usually not needed before 20 weeks

30mg of elemental FE 325 mg ferrous gluconate

Fe supplements

Ferrous sulfate ( 65mg elemental Fe)

Ferrous gluconate (35mg of elemental Fe)

PLATELETS

Progressive decline in count from 1st-3rd tri Increased platelet destruction Gestational thrombocytopenia of pregnancy

Burrows @Kelton reported an 8% prevalence

Plts range between 70-150,000.

Diagnosis of exclusion

?PET/HELLP, ITP, viral disease, HIV, autoimmune disease, ie lupus

OTHER HEMATOLOGIC CHANGES

Leukocytosis secondary to neutrophils Estrogen induced Cortisol induced

Altered immune status Modulation away from cellular immunity

towards humoral immunity Paradoxical decline of immunoglobins A,G,M Only IgG crosses the placenta

URINARY SYSTEMAnatomic Changes Renal hypertrophy Dilation of renal pelvis/calyces

15mm on the right in 3rd trimester

5mm on the left

Predisposition to pyelonephritis in the presence of asymptomatic bacteriuria

Dilation of ureters to 2 cm Mechanical compression Progesterone-induced smooth muscle

relaxation

BLADDER CHANGES

Bladder trigone elevation occurs with increased vascular tortuosity throughout the bladder leading to microhematuria

Decrease bladder capacity

Increased frequency of urinary incontinence

RENAL HEMODYNAMICS

Renal blood flow increases 50% GFR increases 50% (120cc/min180cc/m) Serum Creatinine and BUN levels decrease Glycosuria occurs due to exceeding of

maximum tubular reabsorptive capacity No increase in proteinuria

UTI

Pre-existing renal disease

PET

DIGESTIVE TRACT CHANGES

Addition of 300 kcal/day Gingivitis of pregnancy

Violaceous pedunculated lesion

Epulis gravidarum Stomach

Delayed emptying during labor

Gastroesophageal reflux disease (GERD)

Esophageal dysmotility

Gastric compression due to enlarging uterus

Decrease sphincter tone

Small bowel

Motility is reduced due to progesterone allowing for more efficient absorption

Large bowel

Decreased transit times allows for both water and sodium absorption

Increased portal hypertension leading to dilation wherever there are portosystemic venous anastomoses

Gallbladder Decreased rate of emptying due to

progesterone Cholesterol saturation is increased while

chenodeoxycholic acid is decreased in bile favoring stone formation

Liver Size and histology are unchanged Clinical and laboratory changes mimic disease

states Spider angiomas and palmar erythema Serum albumin and total protein decrease Serum alkaline phosphatase activity Other LFT’s are unchanged

SKELETAL AND POSTURAL CHANGES

Lordosis of pregnancy~ progressive increase in anterior convexity of the lumbar spine

Preserves center of gravity Ligaments of the symphysis and sacroiliac

joints loosen during pregnancy due to relaxin

ENDOCRINE CHANGES

Thyroid Physiology Euthyroid state Increase in thyroxine-binding globulin Decrease in circulating pool of extra-thyroidal

iodide Slight thyromegaly Free T4 and T3 remain normal Small amounts of TRH @T4 cross the placenta Fetal thyroid active by 12 weeks gestation

Adrenal function Increases in corticosteroid-binding globulin Increases in free cortisol Zona fasciculata is increased Marked increase in CRH from placental

sources Delayed plasma clearance of cortisol due to

renal changes Resetting of hypothalamic-pituitary sensitivity

to cortisol feedback on ACTH production

Pituitary gland Enlarges due to proliferation of prolactin-

secreting cells Enlargement makes it more susceptible to

alterations in blood flow, ie PPH Prolactin levels are increased (ten times higher

at term) to prepare breasts for lactation

Pancreas and Fuel Metabolism Physiologic glucose intolerance to insure

continuous transport of nutrients from mother to fetus

Fasting hypoglycemia Postprandial hyperglycemia Hyperinsulinemia

FUEL METABOLISM

Pregnant prolonged fasting Increased utilization of fat stores Lipolysis generates glycerol, fatty acids and

ketones for gluconeogenesis and fuel More HPL, less insulin results in increased

utilization of fat stores Maternal response to starvation

Hypoglycemia, hypoinsulinemia

Hyperlipidemia, hyperketonemia

Maternal response to feeding

Hyperglycemia,

Hyperinsulinemia,

Hyperlipidemia,

Resistance to insulin Insulin secretion increases throughout Insulin resistance increases to 50-80% in third

trimester Borderline pancreas function leads to GDM

ENDOCRINE CHANGES

Diabetogenic effects of pregnancy

HPLlipolytic and anti-insulin

Cortisol

Prolactin

Estrogen and progesterone Fetal glucose levels are 20 mg/dL less than

maternal values Placental glucose transport is carrier mediated

facilitated transport that is energy independent

FUEL AND METABOLISM

Lipids and lipoproteins increase in pregnancy Total cholesterol, LDL, HDL and triglycerides

all increase Necessary as precursors for steroidogenesis Does not appear to lead to atherosclerosis

unless pre-existing hyperlipidemia

PLACENTAL TRANSPORT OF NUTRIENTS

INTEGUMENTAL CHANGES

Hyperpigmentation 90% of pregnancies Localized to areas of increased melanocytes Choasma of pregnancy

70% of women

All races

Up to 30% of changes can persist

Hair Changes Mild hirsutism is common Excessive virilization should prompt

investigation for androgen-secreting tumors Normal pregnancy increases amount of hair in

anagen phase(growth) Postpartum, telogen effluvium may occur with

increased amount of hair in resting phase which leads to loss

OCULAR CHANGES

Increased thickness of the cornea Edema induces a 3% increase Affects contacts

Decreased intraocular pressure Glaucoma improves Minimally decreases visual fields