Book of Medical Disorders in Pregnancy - Tintash

cerning the disturbance in the Renin
angio tensing II aldosterone disruption
by coupling it with his own theory of the
role of prostaglandins. His theory postulates
that an imbalance is found between
the systemic vasodilatory mechanisms
and the effect of Renin and Angiotensin
II which produces vasoconstrictive
effect.
Plasma renin levels are higher in
pregnant normotensive women than in
non pregnant normotensive women although
there is some overlap in values.
Angiotensinogen levels are markedly
elevated in pregnancy probably in
response to estrogen.
The entire Renin angiotensin aldosterone
mechanism is increased but the reason
for this is not clear. It may be that the
system is increased to produce the
required increase in blood volume
associated with increased vascular
capacity in pregnancy. As such the
elevated aldosterone levels are not a
cause of excessive sodium retention but
may represent a compensatory response.
The usual physiological changes
affecting renal renins do not affect
uterine renin. The uterine renin is
probably manufactured mostly in the
chorion.
Chronic Uterine ischemia results in
hypertensive hypernatremic pro-teinuric
dogs (Hodari 1976), toxemia was
associated with a 40 to 60% re-duction
of blood flow in the utero-placental unit.
Gant (1974) has however demonstrated
an increase in Dehydro epiandrosterone
Sulphate clearance early in the
pregnancy of hypertensive patients,
reducing to less than normal prior to the
development of the clinically evident pre
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eclamptic toxemia. This and other
studies have suggested that there is a
declining placental blood flow.
Reduction in Uterine blood flow results
in outpouring of renin into uterine vein
(in pregnant rabbits) •. Angiotensin-II
infusions acutely elevate B.P. in Rh
monkeys and PgE2 in uterine veins and
this is associated with an increase in
blood flow to the uterus. There seems to
be a problem with autoregulation of
blood flow which produces such systemic
effects.
Definitions - The definitions presented
here are those adopted by the Adhuc
Committee of the American College of
Obstetricians and Gynecologists.
Gestational edema - This is defined as
more than one plus of edema after 12
hours of bed rest or weight gain of 5
pounds or more in one week.
Gestational proteinuria - This is
defined as proteinuria in pregnancy
without evidence of hypertension, renal
disease (vascular or infective) or edema.
Proteinuria: This is an important sign
of pre-eclampsia. Proteinuria is usually
defined as the presence of 500 mg or
more of protein found in 24 hour urine
collection or a protein measurement of
2+ or greater in a random urine specimen.
It is important to note that the degree of
proteinuria may fluctuate widely over
any 24 hours period even in severe
cases. Random sampling is thereby some
what less accurate.
Pre eclampsia - This is defined as hypertension
with proteinuria and/or edema