Saturday, March 14, 2009

PREGNANCY-CHANGES IN MOTHER DURING PREGNANCY

CHANGES IN MATERNAL PHYSIOLOGY DURING PREGNANCY

Gestation
Period between conception and birth
Pregesterone/Oestrogen
Female hormones
Erythropoietin
Hormone secreted to increase the numbers of red blood cells
Trimester
A period of 3 months - during pregnancy there are three trimesters
Gravid
Pregnant - “Gravid uterus” means pregnant uterus
FEV
1
Forced Expiratory Volume in 1 minute
FRC
Functional Residual Capacity -
see Update in Anaesthesia (2000) 12;42
Parturient
A patient who is about to or is giving birth
Palmar erythema
Reddening of the palm of the hand

Maternal physiology undergoes many changes during
pregnancy. These changes, which are largely secondary to
the effects of progesterone and oestrogen, begin as early as
4 weeks gestation and are progressive. In the first 12 weeks
of pregnancy progesterone and oestrogen are produced
predominately by the ovary and thereafter by the placenta.
These changes both enable the fetus and placenta to grow
and prepare the mother and baby for childbirth.
Haematological
Red cell mass, white cell count and platelet production
are all increased during pregnancy. The rising white cell
count during pregnancy, which peaks after delivery, can
make diagnosis of infection difficult. Platelet production
is increased, but platelet consumption increases more,
causing the platelet count to fall to low normal values.
Renal erythropoietin production increases leading to a
20% increase in red cell mass.
Increased concentrations of progesterone and oestrogen
directly act on the kidney causing the release of renin. This
activates the aldosterone-renin-angiotensin mechanism
leading to renal sodium retention and an increase in total
body water. Plasma volume increases by 45% and as this
increase is relatively greater than the increase in red cell
mass, maternal haemoglobin concentrations falls from 150
g per litre pre-pregnancy to 120 g per litre during the 3rd
trimester (Figue 1). This is termed physiological anaemia
of pregnancy.
The increased circulating volume offers protection
for mother and fetus from the effects of haemorrhage
at delivery. Knowledge of this is important for the
anaesthetist as it can delay the onset of classic signs and
symptoms of hypovolaemia. It is very easy to be misled
into thinking that, even in the presence of considerable
volume loss, it does not need replacement. This is wrong,
it being essential to replace the measured loss, and to be
aware that more volume may have been lost than the blood
pressure and pulse might indicate. By two weeks post
partum the haematological changes have mostly reverted
to pre-pregnancy status

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