1. Maternal Physiology of Pregnancy
Welcome to OB/Gyn
Intro:
Maternal adjustments to pregnancy are designed to support the requirements of fetal homeostasis and growth
without unduly jeopardizing maternal well-being
Think about it theleologically:
(I.e. from an evolutionary viewpoint)
If one were playing God, how would you change a woman’s physiology so that she is best adapted to support a pregnancy?
Jason K. Baxter, MD, MSCP
Medical Director, Inpatient Obstetrics
Director, Division of Research
Department of Obstetrics and Gynecology
Division of Maternal-Fetal Medicine

2. Maternal Physiologic Changes
Hormonal
Breasts
Cardiovascular
Hematologic
Respiratory
Gastrointestinal
Urinary
Reproductive Tract
Musculoskeletal
Dermatologic
No matter what field you go into, all of you will either be pregnant, help take care of a pregnant spouse or family member, take care of pregnant patients, or at the very least… if you don’t have any friends or family, your neighbors will ask you about normal conditions of pregnancy because they know that you’re a doctor.
“I need your help: What are some of the normal changes that we see with pregnancy?”
“What organ systems are affected by pregnancy”: Bring up one part at a time
Overview: Maternal physiologic changes of any single organ system could fill an hour long lecture
Neurological?
Psychiatric?

3. Hormonal (b-HCG) Produced in the syncytiotrophoblasts of the placenta
Stimulates corpus luteum to produce progesterone and estradiol
Doubles every 48 hrs in first trimester
Human chorionic gonadotropin
Detectable (i.e. >25mIU/ml) at 7 days post fertilization (4-5d post implantation)
Early morning (highest concentration of B-HCG)
(serum vs. urine)
Stimulates corpus luteum to produce progesterone and estradiol until placenta capable of autonomous steroidogenesis
Plateau or decrease with ectopic or spontaneous abortion
1,000–2,000mIU fetal pole and cardiac activity (via TVUS)
Peaks (100,000mIU) 8-10 weeks after LMP, then decreases
Nausea, hyperemesis gravidarum
“Morning sickness”
Alpha subunit (same as LH, FSH & TSH)

4. Hormonal (cont’d) Progesterone HPL: Diabetogenic state Thyroid
Maintains pregnancy
Produced by corpus luteum
Placenta takes over at 9 weeks
Relaxation of smooth muscle
HPL: Diabetogenic state
Thyroid
Prolactin increased
HPLplacental hormones: diabetogenic effect of pregnancy (secreted in proportion to placental mass)
Resistance to insulin
Prolactin increased
FSH/LH decreased or normal, Growth Hormone decreased
Thyroid: Normally, shows moderate Enlargement in pregnancies
Function unaffected (euthyroid), but…
TFTs affected:
Thyroid-binding globulin (TBGs): increased secondary to estrogen-stimulated hepatic synthesis
Increased Total T3 and T4 (a significant portion of each bind to TBG)
Free T3 and free T4 unchanged
TSH unchanged
True hyperthyroidism: elevated free T4
True hypothyroidism: elevated TSH
T3,T4,TSH can diffuse across placental membrane, but transfer is negligible
Thyroid Stimulating Immunoglobin and PTU (propylthiouracil) do cross placenta
Pituitary?
Increased Estrogen also causes inceased clotting factors

5. Breasts Enlarge (first sign) Ducts (estrogen) Areoli (progesterone)
Prolactin
Teleologically why is breast development important during pregnancy?
Why might it be important for the alveoli to darken?

6. Cardiovascular Cardiac Output = Stroke Volume x Heart Rate
Increase:(30-50%) (20-35%) (5-15%)
As early as 10 weeks
Increased blood flow to uterus, placenta, breasts
Cardiac Output further increases up to 40% additionally during 2nd stage of labor
Increases more postpartum

7. Cardiovascular (cont’d)
Increased blood flow
Uterus
Breasts
Skin
Kidneys
Peripheral vascular resistance decreases
Blood flow increases more with gestational age
What organ systems?
Kidney: elimination of waste
Skin: Elimination of heat

8. 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
BP falls from first trimester to the middle of the second trimester
BP increases to prepregnancy levels by term
Systolic decreases 4mm Hg
Diastolic decreases 10-15mm Hg
Venous compression
Decreased venous return
Decreased cardiac output
Compensatory rise in peripheral resistance minimizes fall in BP
10% show decreased BP: nausea, dizzy, syncope
Epidural peripheral sympathectomy, therefore cannot increase peripheral resistance, therefore decreased BP (and fetal distress)

9. Cardiovascular (cont’d)
Displaced upward and left
EKG: Left axis deviation
Chest X-ray: cardiomegaly
Hyperdynamic state
Systolic ejection murmurs
S3 gallop
Distended neck veins
Anatomically:
B/c the diaphragm is elevated 4 cm
Heart is in more horizontal position
EKG: non-specific ST changes
Signs you’ll notice on physical exam

10. Hematologic Blood Volume Increases 30–40 % (1500cc)
Hemodilution of pregnancy
“Physiologic anemia”
Plasma volume increases 50%
Blood volume increases 30 – 50 %
RBC Mass increases 35%
Therefore hematocrit decreases approximately 5%
Usually to the g/dl range, but RBC count does not decrease

11. Hematologic (cont’d) Iron stores decrease Increased WBCs
Actively transported to fetus
1000mg additional iron needed
Increased WBCs
Decreased platelets
WBC counts increase slightly (10-14K), higher in labor and early puerperium (14-16K)
May be as high as 25-30K without infection
Platelets slightly lower, but outside of normal range should be considered abnormal
(Gest. Thrombocytopenia, HELLP, etc.)

12. Hematologic (cont’d) Hypercoaguable state Thromboembolism risk
x 2 in pregnancy
x 5.5 in puerperium
Coagulation factors 1(Fibrinogen),2,7,8,9,10 increased due to increased hepatic synthesis
Increased risk of thromboembolism (late 3rd trimester and puerperium)
Pulmonary embolism 2nd leading cause of maternal mortality
(1st cause is hemorhage)
Caused by Estrogen

13. Respiratory Mechanical changes Upper airway Chest wall
Mucosal congestion, edema
Chest wall
Increased AP diameter
Flaring of the ribs
Elevated diaphragm
Increased nasal congestion and increased nasal secretions
Pts. C/o allergy-like symptoms and chronic colds
epistaxis
From enlarging uterus and relaxing effects of progesteron:
Subcostal angle increases from 68 to 103 degrees
diaphragm is pushed 4cm upward, but..
The AP diameter of the chest increases two cm
The circumference increases 5-7 cm
Non-pregnant: Pregnant ABG:
pH = pH =
pO2 = pO2 = 104 –108
pCO2 = (40) pCO2 = 27 – 32 (30) Hyperventilation with increased tidal volume
HCO3 = 22 –28 (25) HCO3 = 18 – 24 (20) decreased due to increased renal excretion to compensate for mild respiratory alkalosis
Why? Better transport of O2 to baby
Dyspnea from elevated diaphragm, unusually low CO2 of pregnancy)
Decreased Exercise tolerance

14. Respiratory (cont’d) MV = TV x RR Increased tidal volume (40%)
Hyperventilation
Mild, compensated, respiratory alkalosis
Physiologic dyspnea
Increased total body O2 consumption
Respiratory rate: unchanged or slightly increased
Vital capacity: unchanged
Total lung capacity: slightly decreased secondary to residual volume decreased (diaphragm raises 4 cm)
MV = TV x RR
TV: volume inspired & expired with each breath
ERV: max that can be addt’lly expired after normal expiration
RV: volume of air remaining in lungs after max expiration
VC: max that can be forcibly inspired after after a max expiration
IC: max that can be inspired from resting expiratory level
FRC: volume in lungs at resting expiratory level
MV: volume inspired or expired in one minute

15. Gastrointestinal Decreased GI motility and tone Poor esophageal tone
Delayed gastric emptying time
Constipation
Hemorrhoids
Poor esophageal tone
Incompetence of esophageal/ stomach sphincter
Gastric reflux
Heartburn
Secondary to progesterone
Hemorrhoids from constipation and increased venous pressure
Tums/ /maalox
Why constipation? The body conserves water, colon absorbs more water
Appetite

16. Gastrointestinal (cont’d)
Cholestasis
Increased liver metabolism
Alkaline Phosphatase
Cholesterol
Fibrinogen
TBG
Hypoalbuminemia
Decreased colloid oncotic pressure
Epulis of pregnancy
Secondary to progesterone
Higher mortality with appendicitis b/c diagnosis is delayed b/c altered position of appendix
Increased frequency of pancreatitis b/c increased cholelithiasis & hyperlipidemia
Cholelithiasis increased
May need to increase meds metabolized by liver (ie. Seizure meds)
Alkaline phosphatase may be increased as much as two fold
Serum cholesterol levels increased during pregnancy
Hyperemia and softening of the gums (a highly vascular swelling, regresses after pregnancy)

17. Urinary
Renal blood flow and glomerular filtration rate increase 40-50%
Increased renin/ angiotensin system
Increased urinary frequency
Enlarging uterus
Decreased bladder capacity
Therefore decreased BUN, creatinine, uric acid concentrations (increased excretion secondary to increased GFR)
Cr of 1.0 is NOT normal during pregnancy
(glycosuria) not good way to monitor (common Nl finding)

18. Hydronephrosis and hydroureter
Smooth-muscle relaxing progesterone
Dextrorotation of uterus over right pelvic brim
Stasis and risk of infection
Cystitis
Pyelonephritis
Inhibition of peristalsis in ureter
Why
Ureteral dilatation and urostasis
Gram negatives
E.Coli 70-80%
Klebsiella pneumoniae 5-10%
Proteus species 5-10%
Gram positives
Group B streptococci 3-5%
Enterococci 3-5%
Staphylococci 1-3%
Risk of preterm labor
Risk of ARDS

19. Reproductive Tract Uterus Vagina
Distends to 1000 times its normal volume
20% of cardiac output (500ml/min) at term
Vagina
Increased vascularity and distensibility
Leukorrhea of pregnancy
Uterus:
Stretching & hypertrophy (not new cell development)
5-10mL to 5-10L
Estrogen and progesterone up to 14 weeks
Afterwards, direct stretching effect of enlarging fetus
20% versus 1% in non-pregnant patient
(5% myometrium, 10-15% endometrium, 80-85% placenta)
Hegar: (often occurs in early pregnancy)
cervix is distinctly separate from the lower uterus, with soft isthmus in between
Leukorrhea: increased vaginal discharge secondary to increased vaginal capillary permeability and desquamation of vaginal epithelial cells
Hartman: slight spotting as blastocyst implants into endometrium
“light period”: 1 week after ovulation and fertilization (3-3.5 wks post LMP)
sometimes mistakenly used to calculate gestational age
Chadwick: from normal cyanosis of early pregnancy
pH= 4.0

20. Reproductive Tract (cont’d)
Cervix
Ectropion
Chadwick sign? Bluish upper vaginal vault & cervix (normal cyanosis of early pregnancy)
Ectropion: increased eversion of cervical columnar epithelium onto exocervix (may be especially prominent during pregnancy

21. Musculoskeletal Altered center of gravity Progressive lumbar lordosis
Relaxin
Ligamentous symphysis pubis
Diastasis Recti
Carpal tunnel syndrome
Sciatica
How much weight gain ( pounds)
0.5 pound per week for 1st half, 1 pound per week for 2nd half
Prone to fall
laxity of ligaments (progesterone and relaxin)
Low back pain
Median nerve entrapment, fluid retention
Pain, decreased sensation, weakness
Tx: splinting
Decrease salt intake
Improves post-partum

22. Dermatologic Increased pigmentation
Increased estrogen and progesterone
Increased melanocyte-stimulating hormone
Areola, linea nigra, perineum, melasma/chloasma
What is this called?
What hormones cause this hyperpigmentation?
Where?
Teleologically, why does it make sense for the areola to become darker with pregnancy? “Target for baby”

23. Dermatologic (cont’d)
Striae gravidarum (stretch marks)
Vascular spiders (telangiectasias)
Palmar erythema
Hirsutism and acne (progesterone)
Purple or pink initially, become white, silvery: no good treatment (genetic disposition?)
Vascular spiders (telangiectasias): upper torso, face and arms
Palmar erythema in 50% of pregnancies
Like chronic liver disease
Both caused by increased circulating levels of estrogen and both regress after delivery
Hirsutism and acne (progesterone)
Significant hair loss 2 to 4 months post-partum as number of hairs entering telogen (resting state) increases
Due to estrogen

24. Dermatologic (cont’d)
Pruritus gravidarum (elevated bile salts)
Pruritic and urticarial papules and plaques of pregnancy (PUPPP)
Itching in pregnancy
Starts on abdomen )often in stretch marks) and spreads to legs, breasts, etc.
Treated with topical or oral steroids
Resolves postpartum

25. Maternal Physiology in Pregnancy
Hormonal: Progesterone relaxes smooth muscle
Breasts: Enlarge and develop milk production
Cardiovascular: Hyperdynamic state
Hematologic: Hypercoaguable state
Respiratory: Respiratory alkalosis
Gastrointestinal: Decreased motility
Urinary: Urinary stasis
Reproductive: Distensibility & hypertrophy
Musculoskeletal:Center of gravity changed & relaxin
Dermatologic: Increased pigmentation
How would we summarize the maternal physiologic changes on each organ system in pregnancy?
Thank you for your attention
Any questions