Physiologic Changes in Pregnancy

A Systems Review

Physiologic Changes in Pregnancy

A Systems Review

Adaptations Adaptations

• Protect maternal functioning

• Prepare for childbirth & lactation

• Provide nurturing environment

• Meet maternal metabolic needs

Anatomical/Mechanical Adaptations

Anatomical/Mechanical Adaptations

• Uterus enlarges, moves out of pelvis, and affects surrounding organs

Endocrine/Hormonal SystemEndocrine/Hormonal System

• Pregnancy-specific endocrine system controls the integrity & duration of pregnancy

• Many of the physiologic changes during pregnancy are mediated by hormones

PlacentaPlacenta

• Serves as an endocrine gland during pregnancy

• Secretes many hormones, growth factors, and other substances

• Major hormones produced by placenta:– Human chorionic gonadotropin (hCG)– Human placental lactogen (HPL)– Estrogen– Progesterone

hCGhCG

• Major function is to maintain estrogen & progesterone production by corpus luteum until placental function adequate (~ 10 wks)

• hCG levels elevated in multiple pregnancies and low with ectopic pregnancy or abnormal placentation

hPL Human placental lactogen hPL Human placental lactogen

• Principal action of hPL is to increase the supply of glucose to the fetus by decreasing maternal stores of fatty acids

• Alters maternal secretion of insulin

EstrogensEstrogens

• Steroid hormones secreted by ovaries in early pregnancy and the placenta for most of pregnancy

• Prevent further ovarian follicular development during pregnancy

• ↑ blood flow to uterus and stimulates growth of uterine muscle mass

• Prepares breasts for lactation• May initiate onset of labor

ProgesteroneProgesterone

• Acts on uterine muscle to inhibit prostaglandin production

• Acts in other areas of body as well– Relaxes venous walls – Alters respiratory center sensitivity to CO2– Aids in development of lobules of breasts

RelaxinRelaxin

• Inhibits uterine activity, maintaining uterine quiescence during pregnancy; ↓ strength of UCs

• Plays a role in cervical ripening; may help suppress oxytocin release during pregnancy

Prostaglandins (PGs)Prostaglandins (PGs)

• Affect smooth muscle contractility • Causes onset of labor, myometrial

contractility, & cervical ripening

ProlactinProlactin

• Released from anterior pituitary• Matures mammary ducts and glands• Initiation of lactation after birth• Increased levels in pregnancy– Lactation inhibited due to high estrogen

levels– Levels decrease after delivery of

placenta which then allows lactation.

Hematologic SystemHematologic System• Anatomic Changes– Heart Position• shifts upward and to the left

– Heart Size• increased due to blood volume & cardiac

output

– Auscultatory – change in heart sounds• Systolic murmur (90%-95% of women)-only

during last 2 trimesters

Hematologic ChangesHematologic Changes

• Normal pregnancy is associated with 30-50% increase in plasma volume between 6 and 24 weeks.

• Normal pregnancies at the same time only have an increase of RBCs of 15-30% causing a normal reduction in hemoglobin levels.

Hematologic ChangesHematologic Changes

• WBC’s– starts to during 2nd trimester, and peaks

in 3rd trimester– Peaks at 9,000-15,000 prior to labor– 10,000-16,000 during labor, may reach as

high as 29,000

Hematologic Changes Hematologic Changes

• Platelets– unchanged or slightly

• Coagulation factors– Fibrinogen – Factors V, VII, VIII, IX, X, XII – Prothrombin slightly or unchanged– Bleeding & clotting times unchanged

Hemodynamic ChangesHemodynamic Changes

• Cardiac Output – High Flow State 30-50% over pre-pregnant– Begins early, ~ 50% of occurring by 8 wks

gestation, peaks in 2nd trimester, and plateaus until term

– Positional changes (most dramatic at term)- Optimized in lateral position

– Somewhat decreased in sitting position–Markedly decreased in supine

Cardiac Output ChangesCardiac Output Changes

• UCs ( approx. 300-500 ml)• Progressive rise in CO during labor– Latent phase 15%– Active phase 30%– 2nd Stage 45%– Immediate PP 65%

Hemodynamic ChangesHemodynamic Changes

• Heart rate ↑15% or 15-20 bpm– Heart rate increases when sitting or

supine positions up to 40% with multiple gestation

• Sinus Arrhythmias– PAC, PVC, skipped beats–Momentary pressure in neck or chest

Hemodynamic Changes Hemodynamic Changes• Blood Pressure–SBP & DBP in 1st trimester,

lowest in 2nd trimester, gradually toward pre- pregnancy levels by term

–Caused by progesterone & vasodilation

–BP varies with age, activity, anxiety, position, health problems

–Cuff size

BP Considerations BP Considerations

• A difference of 5-10 mmHg between arms is common

• SBP in lower extremities is usually 10mmHg higher than reading in upper extremities

• Obtaining an orthostatic BP can cause the SBP to fall 10-15 mmHg and the diastolic to rise slightly by ~ 5 mmHg– Always obtain pulse rate with orthostatic

BP’s

BP Considerations BP Considerations

• Establish baseline BP early• Consistent arm, arm position,

posture• BP’s with UC’s, pain, and anxiety

CV System: Clinical SignificanceCV System: Clinical Significance

• Arrhythmias– Conversion techniques

• Supine Hypotension Syndrome– 2nd half of pregnancy, uterus compresses

vena cava causing SBP ( up to 30 mmHg), CO by half

–Weakness, lightheaded, dizziness, nausea, syncope

– Interventions• Hypervolemia– To accommodate uterine vasculature, provide

hydration, fluid reserves for birth/PP

Clinical SignificanceClinical Significance

–Anemia • True anemia < 11mg/dL or hct < 33%• RBC mass with iron supplementation

–Hypercoagulation in Pregnancy• Risk of thromboembolic disease• DVT prophylaxis• Anticoagulation therapy

Factor V Leiden MutationFactor V Leiden Mutation

• Also known as Activated Protein C Resistance

• Most common cause of inherited thrombophilia in caucasions

• 3-10x ↑ risk clotting when pt. has 1 copy of the gene, and 30-140x greater if 2 copies of gene

DVT ProphylaxisDVT Prophylaxis• Coumadin

– Inhibits Vitamin K coagulation– Crosses placenta– Risks: abortion, fetal anomalies (face, bones, eyes, CNS)

• Heparin/Lovenox– Inhibits formation new clots– Does not cross placenta or into breast milk– Costs more than Coumadin, more difficult to regulate– SQ administration– Maternal risks: Bruising, tissue irritation, transient

thrombocytopenia, bleeding– Fetal risks: premature, stillbirth

Cardiovascular System - PPCardiovascular System - PP

• HR & atrial size return to pre-preg. values in 1st 10 days PP

• Left ventricular size normalizes at 4-6 mo.

• Plasma volume returns to normal by 6-8 wks, and may be as early as 2-3 wks

• CO ↑ 24-48 hrs after birth, then progressively over 6-12 wks PP

Respiratory System Respiratory System• Anatomic Changes–Diaphragm • Upward shift 4-7 cm.

–Chest/Ribs• Chest circumference 5-7 cm.• Ribs flare

–Abdomen• Abdominal muscle tone • Diaphragmatic/thoracic breathing

Respiratory System Respiratory System

• Lung Volumes –Respiratory Rate (slight

or no change)

–Tidal Volume (Vt) 30-40%

–Functional Residual Capacity (FRC) 20-25%–Minute Ventilation 30-40%

(almost 50% by term)

Gas ExchangeGas Exchange

• Arterial Blood Gases

Pregnant Non-pregnant

• pH 7.40 - 7.45 7.35 - 7.45• pO2 104 - 108 mmHg 90 - 100 mmHg• pCO2 27 - 32 mmHg 35 - 45 mmHg• HCO3 18 -22 mmHg 22 - 26 mmHg

Gas ExchangeGas Exchange

• O2 consumption increases by almost 20% during pregnancy to meet the increased metabolic demands of the placenta, fetus and maternal organs

Respiratory – Clinical SignificanceRespiratory – Clinical Significance

• Pregnancy is a state of relative hyperventilation, which may be centrally mediated through progesterone. The respiratory rate does not change while tidal volume increases, resulting in an approximately 50% increase in minute ventilation

Respiratory – Clinical SignificanceRespiratory – Clinical Significance

• Increased blood flow to the nasopharynx may cause pregnant women to complain of congestion

• Pregnant women may develop a benign growth increasing this congestion

Respiratory System Respiratory System

• Postpartum–Return to Normal Within 1 to 3

Weeks, Except for Rib Cage Flaring

Renal System Renal System• Anatomic Changes– Kidneys• Slight in weight & size

– Urinary Collecting System• Ureters dilated & elongated, tortuous,

motility and tone • Urethra lengthens

– Bladder• Displaced forward & upward in late

pregnancy; convex to concave shape• Urine output • Urine frequency in 60% of pregnant women;

incidence in stress & urge incontinence

Renal Function ChangesRenal Function Changes

• Renal Plasma Flow (RPF) 60-80% by mid-second trimester,

then 50% above pre-pregnancy by 3rd trimester

• Glomerular Filtration Rate (GFR) 40-50% by early 2nd trimester clearance of creatinine, BUN, &

uric acid

Renal Function ChangesRenal Function Changes

• Sodium & Water Metabolism– 2 to 6 mEq of Na are reabsorbed daily to

meet fetal/maternal needs, causing an increase in body water weight

Nutrient Excretion Nutrient Excretion

–Glucose (due to 50% in GFR)

–Amino acid

–Urinary protein loss

–Folate & Vitamin B12

–Bicarbonate excretion

Clinical Significance - RenalClinical Significance - Renal

• Hydronephrosis/Hydroureter (80%) risk UTI’s– Difficulty diagnosing urinary tract

obstructions, radiology & renal tests

• Bladder– Stress incontinence– Edema risk trauma during labor/birth– Potential for infection

PostpartumPostpartum

• Hemodynamic changes– Renal volume RTN within first week– Creatinine clearance values return to

non-preg. by 6th day postpartum

• Anatomic changes– Hydronephrosis & hydroureter may last

as long as 6-12 weeks after delivery

Gastrointestinal SystemGastrointestinal System• Anatomic/Physiologic Changes–Mouth and Pharynx• Hyperemia, edema of tissue & gums in saliva production

– Esophagus and Stomach• Lower esophagus sphincter

pressure• Pyloric incompetence (bile reflux)• Tone & motility • Acidity

GI System GI System

• Intestines and Colon– Displaced upward and laterally– Tone & motility

• Gallbladder– Size – Position more horizontal– Hypotonic & distended

• Appendix– Displaced from gravid uterus,

higher and more to the right

Liver Function Liver Function

• Pushed superior & posterior

• Function altered in pregnancy– Alkaline phosphatase 2-4x– Cholesterol levels double – Plasma albumin to 3.0 g/dl– Fibrinogen 50%– Serum levels of bilirubin, AST/SGOT,

ALT/SGPT unchanged

Metabolic ChangesMetabolic Changes• Hypoglycemia–Pancreas stimulated to insulin secretion–Glycogen storage & peripheral

glucose utilization –Hepatic glucose production & FBS

levels –Glucose & amino acids used for

fetal growth and development

Metabolic ChangesMetabolic Changes

• Hyperinsulinemia – Glucose levels as pregnancy progresses free fatty acids & ketones mobilized for

maternal energy (so glucose available for fetal needs)

• Insulin resistance during later half of pregnancy insulin production – Effects of rising levels of prolactin and

maternal cortisol and glucagon

Clinical Significance - GI SystemClinical Significance - GI System

• Diagnosis of Appendicitis– Displacement of appendix by gravid uterus

• Aspiration LES competence, delayed stomach emptying

time, gastric acid secretion, tone/gastric motility

• Peptic Ulcers– Acid secretion in 1st/2nd trimesters, delayed

gastric emptying, gastric mucous secretion, protective effect of prostaglandins on gastric mucosa

Nausea In PregnancyNausea In Pregnancy

• High levels of hormones progesterone and b-HCG slow digestion and promote formation of intestinal gas

• Low blood sugar

• Fatigue and lack of exercise

• Deficiency in B vitamins

• Increase in T4, results in smooth muscle relaxation in the stomach

Nausea in PregnancyNausea in Pregnancy

• Symptoms begin between 4-6 weeks of pregnancy.

• Usually improve by the 15-20 weeks

• Aggravated by ptyalism (excessive salivation)

Hyperemesis GravidariumHyperemesis Gravidarium

• Associated with weight loss, ketonemia, electrolyte imbalance, possible liver and renal damage

• Treatment– IV replacement, fluids, electrolytes– Antiemetics (po, IV, suppository, Zofran

SQ pump)– Vitamin B6 50 mg, Unisom– Psychological support

Dietary ChangesDietary Changes

• Small frequent meals• Avoid oily or spicy foods• Protein snack before sleeping• Eating before arising (crackers, etc.)• Drink liquids separate from meals• Well-balanced, varied, whole foods diet

with little or no processed foods• Minimize odors in room (remove tray cover

before taking meal tray into room, etc.)

Herbal SupplementsHerbal Supplements

• Ginger root (Zingiber officinalis)– Powdered, 250 mg capsules 4x daily

• Fresh ginger root as a tea, steeped in boiling water x 15 min. and sipped slowly throughout day; sweeten with honey

• Chamomile tea (Maricara recutita) sipped throughout day, especially at bedtime

• Peppermint tea (Menthe piperata), dried or fresh leaves (not the essential oil)

Herbal SupplementsHerbal Supplements

• Cinnamon or peppermint candies

• Raspberry leaf tea (Rubus idaeus), 1-2 cups per day, steeped 5 min. or less; use 1 tsp of dried herb for 1 cup of boiling water

PrecautionsPrecautions

• Do not use high dose of vitamin B6 in the 3rd trimester (may decrease breast milk and/or cause rebound B6 deficiency in baby)

• Do not use essential oil of peppermint internally

• Do not use herbal tinctures because of alcohol content

Herbal CautionsHerbal Cautions• FDA has no regulatory mechanism to

ensure either the quality of raw materials or manufacturing process for herbs.

• Be careful in the selection of the type of herb as well as the company that manufactures it.

• List of FDA dietary supplement recalls available online at www.fda.gov

Herbal CautionsHerbal Cautions

• The United States Pharmacopoeia (USP) recently began the Dietary Supplement Verification Program (DSVP) – a voluntary program to certify dietary supplements for quality (www.usp.org)

• Products that meet the USP’s standards for purity, accuracy of ingredient labeling, and manufacturing practices are granted the right to add a USP certification mark to the labeling

GI SystemGI System

• Constipation motility, H2O absorption from colon,

uterine pressure, iron in PNV– Interventions

• Hemorrhoids– Hyperemia of pelvic organs, pressure

gravid uterus, straining from constipation– Relief measures

Intrahepatic Cholestasis of Preg. (IHCP)

Intrahepatic Cholestasis of Preg. (IHCP)

• Results from retention and accumulation of bile in the liver

• Pruritis gravidarium: itching, anorexia, malaise, epigastric pain, dark urine, jaundice

• Management– Reassurance, corn starch baths, soothing

ointments, avoid perfumed soaps/toiletries, Ursodeoxycholic acid

CholecystitisCholecystitis

• Gallstone formation from incomplete emptying & residual volume of cholesterol crystals in gallbladder–S/S: RUQ pain, N/V, weight loss,

intolerance to fatty foods, fever–Management: BR, IV’s, NPO,

antibiotics, possible surgical intervention after r/o other problems

GI SystemGI System

• Weight Gain– 1st half – maternal stores– 2nd half – fetal growth & development– Need to gain 20 pounds to ensure

adequate growth & development• Low BMI (underwt) 28 to 40 pounds• Average BMI (ave. wt) 25 to 35 pounds• High BMI (overweight) 15 to 25 pounds

Weight DistributionWeight Distribution

Pounds

• Fetus, placenta, amniotic fluid 11

• Uterus, breasts 2

• Blood volume 4

• Maternal stores 5

• Tissue, fluid 3

Total 25

Gastrointestinal SystemGastrointestinal System

• Postpartum–Weight Loss 12 pounds in 3 mo.– Lower Esophageal Sphincter (LES)

Competence – returns ~ 6 wks– IHCP (intrahepatic cholestasis of

pregnancy) – disappears shortly after delivery (within days)

– Liver Function – returns to normal about 3 weeks PP

Musculoskeletal SystemMusculoskeletal System

• Anatomic/Physiologic Changes– Ligaments• Ligaments soften early in pregnancy; affected

most - sacroiliac, sacrococcygeal, pubic joints

– Lumbar Lordosis• Spinal curve progressively , keeps center of

gravity over legs, accommodates wt. of uterus

– Diastasis Recti – rectus abdominis muscle seperates due to pressure from gravid uterus.

MusculoskeletalMusculoskeletal

• Anatomic/Physiologic Changes– Skin changes

diaphoresis• Mask of pregnancy

– Calcium Metabolism GI reabsorption & renal excretion• Maternal total serum Ca until 34-36

wks, then slightly . No loss of bone density in pregancy

Musculoskeletal System Musculoskeletal System

• Clinical Significance–Joint/Ligament Softening• Facilitates vag birth, pelvic

discomfort late in preg., gait unsteadiness (falls), “waddle”

–Lumbar Lordosis – low back pain

MusculoskeletalMusculoskeletal

• Postpartum–Most Changes Resolve Within Six

Weeks

Neuromuscular SystemNeuromuscular System

• Physiologic Changes

–Eye• Corneal thickness • Intraocular pressure

• No other nervous system changes, but several discomforts

in DTRs not normal in pregnancy

Clinical Significance - Neuromuscular

Clinical Significance - Neuromuscular

• Ocular changes– Contact lens intolerance, blurred vision,

spontaneous subconjunctival hemorrhages

• Headaches– Mild, frontal 1st/2nd trimesters– Severe – assess for PIH, esp. > 20 wks

• Dizziness/Syncope– Vasomotor instability, postural

hypotension, hypoglycemia

Clinical Significance - Neuromuscular

Clinical Significance - Neuromuscular

• Hypotension• Paresthesias/Tingling– Pressure from gravid uterus interfering with

circulation– Tingling of hands/fingers (hyperventilation,

lumbodorsal lordosis, flexion of neck/shoulder slumping)

• Transient Neuropathies– Bell’s Palsy, carpal tunnel

syndrome, foot drop

NeuromuscularNeuromuscular

• Postpartum–Most Changes Regress by Six

Weeks Postpartum

Reproductive ChangesReproductive Changes

• Uterus– Size , capacity

• Uterine vasculature blood flow from 15-20

ml/min. to 500 ml/min.–Myometrial stretching/thinning beginning

at 5 months

• Cervix vascularity, softening, dilation– Endocervical gland hyperactivity• Mucus plug, mucus production

Reproductive ChangesReproductive Changes• Vagina– Hypertrophy, vascularization, hyperplasia• Connective tissue loosens, mucosa thickens

– Endocervical gland hyperactivity leukorrhea• Vulvar and vaginal varicosities can occur

• Breasts size, nodularity, vascularity– Growth of ducts and secretory glands–Montgomery glands hypertrophy– Colostrum production

Reproductive - PostpartumReproductive - Postpartum

• Involution continues over six to ten weeks postpartum

The End…..The End…..

ReferencesReferencesRoberts, V. Myatt L.(2013) Placental Development and Physiology. UpToDate.Bauer, K. (2014) Factor V Leiden and Activated Protein C Resistance: Clinical Manifestations and Diagnosis. UpToDate.Funai, E., Gillen-Goldstein, J., Roque, H., & Abdel-Razeq, S. (2014) Respiratory Tract Changes During Pregnancy. UpToDate.Bauer, K. (2014) Hematologic Changes in Pregnancy. UpToDateThadhani, R., & Maynard, S. (2014) Renal and Urinary Tract Physiology in Normal Pregnancy. UpToDate.