Maternal Physiology of Pregnancy

Jason K. Baxter, MD, MSCPMedical Director, Inpatient Obstetrics

Director, Division of ResearchDepartment of Obstetrics and Gynecology

Division of Maternal-Fetal MedicineJason.Baxter@jefferson.edu

Maternal Physiologic Changes

HormonalBreastsCardiovascularHematologicRespiratory

GastrointestinalUrinaryReproductive TractMusculoskeletalDermatologic

Hormonal (-HCG)Produced in the syncytiotrophoblasts of the

placentaStimulates corpus luteum to produce

progesterone and estradiol Doubles every 48 hrs in first trimester

Hormonal (cont’d)

Progesterone Maintains pregnancy Produced by corpus luteum Placenta takes over at 9 weeks Relaxation of smooth muscle

HPL: Diabetogenic stateThyroidProlactin increased

Breasts

Enlarge (first sign)Ducts (estrogen)Areoli (progesterone)Prolactin

CardiovascularCardiac Output = Stroke Volume x Heart Rate

Increase:(30-50%) (20-35%) (5-15%) As early as 10 weeks

Cardiovascular (cont’d)

Increased blood flow Uterus Breasts Skin Kidneys

Peripheral vascular resistance decreases

Cardiovascular (cont’d)BP = CO x SVR Inferior vena cava

(supine hypotension) syndrome

Elevated venous pressure in lower extremeties

Varicose veins Venous stasis Leg edema Thrombi Hemorrhoids

Cardiovascular (cont’d)

Displaced upward and leftEKG: Left axis deviationChest X-ray: cardiomegalyHyperdynamic state

Systolic ejection murmurs S3 gallop Distended neck veins

HematologicBlood Volume Increases 30–40 % (1500cc)Hemodilution of pregnancy

“Physiologic anemia”

Hematologic (cont’d)

Iron stores decrease Actively transported to fetus 1000mg additional iron needed

Increased WBCsDecreased platelets

Hematologic (cont’d)

Hypercoaguable state Thromboembolism risk

• x 2 in pregnancy

• x 5.5 in puerperium

Respiratory

Mechanical changesUpper airway

Mucosal congestion, edema

Chest wall Increased AP diameter Flaring of the ribs Elevated diaphragm

Respiratory (cont’d)MV = TV x RR Increased tidal volume

(40%)HyperventilationMild, compensated,

respiratory alkalosisPhysiologic dyspnea

GastrointestinalDecreased GI motility and tone

Delayed gastric emptying time Constipation

• Hemorrhoids

Poor esophageal tone Incompetence of esophageal/ stomach sphincter

• Gastric reflux

• Heartburn

Gastrointestinal (cont’d)Cholestasis Increased liver metabolism

Alkaline Phosphatase Cholesterol Fibrinogen TBG

Hypoalbuminemia Decreased colloid oncotic pressure

Epulis of pregnancy

Urinary

Renal blood flow and glomerular filtration rate increase 40-50%

Increased renin/ angiotensin systemIncreased urinary frequency

Enlarging uterus Decreased bladder capacity

Hydronephrosis and hydroureter

Smooth-muscle relaxing progesterone

Dextrorotation of uterus over right pelvic brim

Stasis and risk of infection• Cystitis

• Pyelonephritis

Reproductive Tract

Uterus Distends to 1000 times its normal volume 20% of cardiac output (500ml/min) at term

Vagina Increased vascularity and distensibility Leukorrhea of pregnancy

Reproductive Tract (cont’d)

Cervix Ectropion

Musculoskeletal

Altered center of gravityProgressive lumbar lordosis Relaxin

Ligamentous symphysis pubis

Diastasis RectiCarpal tunnel syndromeSciatica

DermatologicIncreased pigmentation Increased estrogen and progesterone Increased melanocyte-stimulating hormoneAreola, linea nigra, perineum, melasma/chloasma

Dermatologic (cont’d)Striae gravidarum (stretch marks)Vascular spiders (telangiectasias)Palmar erythemaHirsutism and acne (progesterone)

Dermatologic (cont’d)Pruritus gravidarum (elevated bile salts)Pruritic and urticarial papules and plaques

of pregnancy (PUPPP)

Maternal Physiology in PregnancyHormonal: Progesterone relaxes smooth muscleBreasts: Enlarge and develop milk

productionCardiovascular: Hyperdynamic stateHematologic: Hypercoaguable stateRespiratory: Respiratory alkalosisGastrointestinal: Decreased motilityUrinary: Urinary stasisReproductive: Distensibility & hypertrophyMusculoskeletal:Center of gravity changed & relaxinDermatologic: Increased pigmentation