Book of Medical Disorders in Pregnancy - Tintash

pregnancy. The increase in volume is
probably due to increased production of
aldosterone which occurs in normal
pregnancy. Estrogens also play some
part in increasing this volume.
Blood corpuscles - The white cells increase
from 4000 to 10,000 per cu mm.
The increase is mainly in polymorphonuclear
cells. There is also an
increase in the platelet count which may
rise from 150,000 to 500,000/cu mm.
Heart sounds - It is important for the
student of obstetrics to review normal
functioning of the heart in the non-pregnant
state. He must familiarize himself
with various heart sounds which are
produced by opening and closure of
various heart valves. In my opinion it is
not possible to appreciate abnormal heart
sounds and murmurs unless the student
is adequately familiar with normal heart
sounds and physiological changes which
occur in the blood volume and shapes of
the heart and cardiac output during
pregnancy.
Fig5.4: Shows two cardiac cycles
opening and closing of valves produce
sounds.
Heart sounds
69
The closing of the mitral and tricuspid
valves (known together as the atrioventricular
valves) at the beginning of
ventricular systole cause the first part of
the "lubb-dub" sound made by the heart
as it beats. Formally, this sound is
known as the First Heart Tone, or S1.
This first heart tone is created by the
closure of mitral and tricuspid valve and
is actually a two component sound, M1,
T1.
Second intercostal space, right
sternal border
Aortic
Value
Second and third
intercostal space, left
sternal border
Pulmonary
Value
Mitral Value
Fifth intercostal
space, left
sternal border
Tricuspid
Value
Fifth intercostal
space, midclavicular
line
Fig5.5: Shows principal areas for
auscultation for heart sounds.
The second part of the "lub-dubb" (the
Second Heart Tone, or S2), is caused by
the closure of the aortic and pulmonary
valves at the end of ventricular systole.
As the left ventricle empties, its pressure
falls below the pressure in the aorta, and
the aortic valve closes. Similarly, as the
pressure in the right ventricle falls below
the pressure in the pulmonary artery, the
pulmonary valve closes. The second
heart sound is also two components, A2
and P2. The aortic valve closes earlier
than the pulmonary valve and they are
audibly separated from each other in the
second heart sound. This "splitting" of
S2 is only audible during inhalation.
However, some cardiac conduction ab-