changes in cardiovascular system during pregnancy

1. CHANGES IN THE CARDIOVASCULAR
SYSTEM

2. CHANGES IN THE
CARDIOVASCULAR SYSTEM
For the care of women with normal pregnancies
as well as for the management of women with
pre-existing cardiovascular diseases, an
understanding of these changes is important.

3. THE HEART
• The heart muscle, particularly the left ventricle,
hypertrophies leading to enlargement of the heart.
• The growing uterus pushes the heart upwards and to the
left During pregnancy the heart rate and stroke volume
(the amount of blood pumped by the heart with each beat)
increases.
• This is due to the increased blood volume and increased
oxygen requirements of the maternal tissues and the
growing fetus.

4. • The cardiac output increases markedly by the end
of the first trimester.
• In the third trimester, a rise, fall or no change at all
has been shown to occur, depending on individual
variations.
• Although the cardiac output is increased in
pregnancy, the blood pressure does not rise because
of the reduction in peripheral resistance.

5. • The capacity of veins and venules increases The
increased production of vasodilator prostaglandin
also contributes to this.
• During the mid-trimester, changes in blood
pressure may occur causing fainting. In later
pregnancy, hypotension may occur in 10 per- cent
of women in unsupported supine position. This is
termed as the supine hypotensive syndrome.

6. • The pressure of the gravid uterus compresses
the vena cava, reducing the venous return.
Cardiac output is reduced by 25-30 percent
and the blood pressure may fall by 10-15
percent, which produces the feelings of
dizziness, nausea and even fainting.

7. • Poor venous return in late pregnancy along with
increased distensibility and pressure in the
veins of the legs, vulva, rectum and pelvis can
lead to edema in the lower leg, varicose veins
and hemorrhoids.
• There is increased blood flow to the breasts
throughout pregnancy and dilated veins may be
seen on the surface of the breasts along with
enlargement and tingling from early pregnancy

8. • Blood flow increases to the uterus, kidneys,
breasts and skin during pregnancy. Much of the
cardiac output goes to the utero- placental
circulation, which is about 750 ml per minute .

9. THE BLOOD VOLUME
• The increase in blood volume in pregnancy varies
according to the size of the woman, the number of
pregnancies she has had, her parity and whether the
pregnancy is singleton or multiple
• The increase begins at about tenth week gestation and
progresses up to 30th-34th week of gestation
• The increase may be as much as 100 percent in some
women.

10. A higher circulating volume is required for the
following functions:
To provide extra blood flow for placental circulation.
To supply the extra metabolic needs of the fetus
To provide extra perfusion of kidneys and other
organs
 To counterbalance the effects of increased arterial
and venous capacity
To compensate for blood loss at delivery

11. Plasma Protein
During the first 20 weeks of pregnancy, the plasma
protein concentration reduces as a result of the
increased plasma volume.
This leads to lowered osmotic pressure, contributing to
edema of the lower limbs seen in late pregnancy .
In the absence of disease, moderate edema is seen as
physiological

12. IRON METABOLISM
• Iron requirement increases significantly in the
last trimester, during which time iron absorp-
tion from the gut is enhanced.
• The purpose of iron supplementation in
pregnancy is to prevent iron deficiency in the
mother, not to raise the hemoglobin.

13. CLOTTING FACTORS
• The clotting and fibrinolytic systems undergo
major changes during pregnancy. Plasma
fibrinogen (factor 1) increases from the third
month of pregnancy progressively until term.
Prothrombin (factor 2) increases only slightly.
Factors 7, 8, 9 and 10 increase leading to change
in coagulation time from 12-8 minutes

14. • The capacity for clotting is thus increased, in
preparation for the prevention of hemorrhage
at placental separation. However, there is a
higher risk of thrombosis, embolism.

15. White Blood Cells
• The neutrophils increase in pregnancy, which enhances the
blood's phagocytic and bactericidal properties.
• In the second and third trimester the action of the
polymorphonuclear leukocytes may be depressed, perhaps
accounting for the increased susceptibility of pregnant
women to infection.
• The lymphocyte and monocyte numbers remain the same
through- out pregnancy.

16. IMMUNITY
• Immune response is reduced in pregnancy.
• Levels of immunoglobulins IgA, IgG and IgM decrease
steadily from the 10th week to the 30th week and then
remain at these levels until term resulting in reduced
immune response.
• Antibody titers against viruses, such as measles, influenza A
and herpes simplex, are reduced in proportion to the
hemodilution effect, therefore viral resistance is unchanged