Maternal Physiology Lecture

MATERNAL PHYSIOLOGY
Chukwuma I. Onyeije, M.D.
Atlanta Perinatal Associates
Clinical Assoc. Professor
Morehouse School of Medicine
http://maternalfetalmedicineblog.com
http://onyeije.net/present

Objectives
Detail normal physiologic changes in the following maternal systems:
Cardiovascular
Respiratory
Renal
Hematologic
Gastrointestinal
Reproductive systems.
Describe the implications for these changes for normal and abnormal pregnancies.

Objectives
Review nutritional requirements normal pregnancy
Review components and reasons for the medical evaluation at the first prenatal visit
Give the reason for routine laboratory tests obtained early in pregnancy.

BULLET POINTS:
Dilutional anemia of pregnancy:
Lower hematocrit due to expansion of plasma volume which is greater than the increase in red blood cell mass

BULLET POINTS:
Pregnancy is a Hypercoagulable state:
Increased risk for venous clotting episodes

BULLET POINTS:
Hegar's sign:
Cervix appears bluish and engorged

BULLET POINTS:
MSAFP
(Maternal serum
alpha-fetoprotein)‏
Screening test of maternal blood done in the early second trimester to screen pregnant women for fetal anomalies and chromosomal abnormalities

BULLET POINTS:
Bacterial vaginosis:
Bacterial infection of the vagina associated with preterm labor and birth

BULLET POINTS:
Rhogam:
An antibody preparation of anti-Rh factor given to Rh negative women to prevent Rh isoimmunization

BULLET POINTS:
Neural tube defect (NTD):
An abnormality in closure of the neural tube, resulting in a spectrum of anomalies from anencephaly (no cranium or cerebrum) to spina bifida

BULLET POINTS:
Intrauterine growth restriction (IUGR): pathological condition of abnormal placentation resulting in an undergrown fetus
Small-for-gestational age (SGA): the lower 10% of birthweights

BULLET POINTS:
Large-for-gestational age (LGA): the upper 10% of birthweights
Macrosomia: an abnormally large infant (usually > 4000 gm)

The primary goal of prenatal care is to deliver a healthy term infant without impairing the mothers health and to identify and optimally treat the high-risk mother.

The vast majority of pregnancies are uncomplicated. Excessive intervention during pregnancy can result in less than optimal outcome

THE CARDIOVASCULAR SYSTEM:

THE CARDIOVASCULAR SYSTEM:
Cardiac output increases 30-50%
Stroke volume increases about 10- 15%
Pulse increases about 15-20 bpm
Systolic ejection murmur and S3 gallop are seen in 90% of pregnant women

CARDIAC OUTPUT DURING PREGNANCY

Peripheral vascular resistance falls Blood pressure falls during the second trimester and then returns to normal during the third trimester

CLINICAL SIGNIFICANCE: Many of the NORMAL effects of pregnancy mimic heart failure (edema, gallops, dyspnea, distended neck veins, abnormal cardiac silhouette on CXR, EKG changes).

THE RESPIRATORY SYSTEM:

Lung volumes changes in pregnancy

NO CHANGE: Respiratory rate, Vital capacity, Inspiratory reserve volume

DECREASED: Functional residual capacity Expiratory reserve volume Residual volume Total lung capacity

INCREASED: Inspiratory capacity Tidal volume

BLOOD GASES: CLINICAL SIGNIFICANCE: The normal pregnant woman has a compensated respiratory alkalosis and a diminished pulmonary reserve.

THE RENAL SYSTEM:

ANATOMIC RENAL CHANGES: Kidneys increase in size and weight, Dilatation of ureters (R > L) Bladder becomes an intra-abdominal organ

HEMODYNAMIC RENAL CHANGES: GFR increases 50%, Renal plasma flow increases by 75% Creatinine clearance increases to 150-200 cc/min

METABOLIC RENAL CHANGES
BUN and serum creatinine decrease by 25% Increase in tubular reabsorption of sodium
Increase in glucose excretion

METABOLIC RENAL CHANGES
Plasma osmolarity decreases about 10 mOsm/kg H2O
Marked increase in renin and angiotensin levels, BUT markedly reduced vascular sensitivity to their hypertensive effects

CLINICAL SIGNIFICANCE of RENAL CHANGES
:
Pregnant women are at increased risk for prone to pyelonephritis
Pregnant women are at increased risk for bladder rupture during abdominal trauma.

THE HEMATOLOGIC SYSTEM

Plasma volume and RBC mass Plasma volume increases by about 50% RBC volume increases by about 30%

Plasma volume and RBC mass END RESULT: ”Dilutional anemia of pregnancy", Average hemoglobin during pregnancy is 11.5 g/dl

Plasma volume and RBC mass

OTHER HEMATOLOGIC CHANGES: WBC count increases Platelet count decreases, but stays within normal limits

COAGULATION SYSTEM: Pregnancy is a "hypercoagulable state" Increased levels of fibrinogen, factor VII-X The placenta produces a plasminogen activator inhibitor

CLINICAL SIGNIFICANCE: Blood loss is well-tolerated during labor. However: maternal vital signs DO NOT change for blood loss of up to 1500 cc, Therefore: vital signs cannot be trusted as an indicator of blood loss.

THE GASTROINTESTINAL AND REPRODUCTIVE SYSTEMS

Gastrointestinal System Decreased motility, due to influence of progesterone Reduced gastric acid secretion

Gastrointestinal System CLINICAL SIGNIFICANCE: A pregnant woman is considered to have a full stomach even if she has had nothing to eat or drink for several hours. Peptic ulceration is rare during pregnancy.

Reproductive System Weight of the Uterus increases from 70 gm to 1100 gm Blood flow: increases to about 750 cc/min, or 10-15% of cardiac output

NUTRITIONAL CONSIDERATIONS DURING PREGNANCY

PREGNANCY WEIGHT GAIN BY ORGAN SYSTEM: Fetus: 7 pounds Placenta and amniotic fluid -- 3 pounds Blood volume-- 4 pounds Breasts-- 2 pounds Maternal fat-- 4 pounds ANTICIPATED TOTAL: 20 pounds

Average weight gain THERE IS NO SUCH THING AS “OPTIMAL” WEIGHT GAIN Normal BMI: 20 lbs Underweight BMI: 30 lbs Overweight BMI 16 lbs

Daily dietary requirements Calories: Increased 15% to ~ 2200 cal/day Protein: An additional 10 to 30 gm /day ~ 75 gm/day total Iron supplementation 30 to 60 mg per day

Calcium: 1200 mg needed per day, usually provided by a quart of milk per day or 2 Tums/day, Folate: supplement 200 to 400 mcg per day In women with a prior history of having a baby with a neural tube defect, supplementing with 4 mg per day (4000 mcg) has been shown to decrease the risk of a recurrence in the next pregnancy

The pregnant patient is best served by having a healthy balanced diet with iron and folate supplementation. Only rarely are other vitamin supplements necessary

PRENATAL CARE

The first prenatal visit Decide: Is this patient normal or high-risk?

COMMON COMPLAINTS OF PREGNANCY

Nausea and vomiting: usually dissipates by 15 weeks

Constipation: common throughout pregnancy

Heartburn: often worsens as pregnancy progresses

Vaginitis: treat only if symptomatic

Varicose veins: treat symptomatically

Headaches

Lower extremity edema is very common

Backache: Lordosis is common with change in the center of gravity

Faintness and light-headedness

Carpal tunnel syndrome

REVIEW QUESTIONS:

Which of the following INCREASES in pregnancy?
FRC
ERV
RV
TV

During which of the following states is the blood pressure lowest?
First trimester
Second trimester
Third trimester
Non pregnant

All of the following are increased in pregnancy except:
Renal plasma flow
GFR
Serum creatinine
Tubular sodium resorption

CONCLUSION:
Understanding maternal physiology is crucial in understanding the changes associated in pregnancy

CONCLUSION:
This knowledge will help us distinguish the physiologic and pathologic processes during pregnancy
This knowledge is also necessary to improve patient education about pregnancy

For More Information and Other Maternal-Fetal Lectures, Please Visit: http://maternalfetalmedicineblog.com http://onyeije.net/present http://preeclampsiaonline.net

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Maternal Physiology Lecture

by Chukwuma Onyeije on Dec 06, 2009

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