A humble effort for integrating the physiology of Pregnancy . I hope to add something or help remembering.

1. By D.Mohamed Abdel Bagi Abdel Ghani
M.B.B.S UofK Registerar of obs&gyne

2. Introduction
 All changes in the physiology of the maternal organs
or body system happens to facilitate it all for the fetus
or the expected baby starting from growth inside the
womb till delivery.

3. Cardiovascular and hematological
systems
 The plasma volume expands from about 6.5 L to 8.5 L and
this happens till the 30-34 weeks of gestation.
 The red cell mass or volume increases from 1.4 L to 1.6 L.
 The discrepancy between the rate of increase of plasma
volume and that of red cell mass results in a relative
haemodilution or ‘physiological anaemia’ with the
haemoglobin (Hb) concentration, haematocrit, and red
cell counts all decreasing (particularly in the second
trimester).
 Depletion of iron stores happens during pregnancy
becacuse all iron is directed toward the growing fetus. And
folic acid is excreted largely by the kidneys .That is why we
give folate and iron supplementation during pregnancy.

4.  This expansion of blood leads to the increase in the
stroke volume and heart rate leading to a rise in blood
flow to the maternal organs especially the kidneys and
placenta (Fetomaternal organ).
 This leads to a high Glomerular Filtration Rate this is
together with decrease in oncotic pressure( Albumin)
leads to a low threshold for sodium and water
retention and glucose execretion leading to the normal
oedema of pregnancy.
 For the placenta it eases its functions which are the
feeding of the baby i.e transferring nutrients (glucose
and amin acids) and excreting waste products (co2 ).

5.  Pregnancy is a hypercoagulable state.
 Platelets either remain an changed or slightly decrease
during pregnancy. Almost all procoagulants (VII,VIII,
IX,X,XI, Fibrinogen, von Willebrand factor which is a
carrier of factor VIII and activated protein C
resistance). Also blood has expanded but it becomes
slower than before preg. (Stasis). That is why during
pregnancy the risk of thromboembolism increases 5
times the normal.
 But Also the Fibrinolytic system activity increases
(tissue plasminogen activator converts plasminogen
into plasmin, which cleaves fibrin and fibrinogen,
yielding fibrin degradation products).Why? possibly to
counterbalance the increased coagulation state.

6.  Again why is the increase of the coagulation state?
 Because at delivery with placental separation and the
flow of about 500 ml of blood per minute in the
placental bed if there is no an efficient haemostasis
the woman will die from extensive blood loss.

7. Cardiovascular s.
 The heart enlarges (hypetrophies).
 The heart rate * Stroke Volume = Cardiac output all
increase as we said.
 But the peripheral resistance decreases probably due to the
increase in the production of vasodilator prostaglandins.
This is why Blood Pressure decreases by about 10-20 mmgh
in mid pregnancy.
 Enlarged uterus vena caval compression supine
hypotension syndrome.
 Enlarged uterus Aortic compression a difference in
the brachial and femoral artery pressures ( so a difference
between BP when lying supine or in the Lateral position).

8. Respiratory system
 Ventilation increases but the respiratory rate RR is
unchanged during pregnancy. The increase in co2 (from
mother and baby)stimulates the respiratory center in the
mid brain plus the progesterone effect
(Bronchconstriction) causes the rise up of ventilation. And
in part by the rise up of the diaphragm.
 Minute ventilation= is the amount of the air moved in and
out of the lungs in 1 minute. It increases during pregnancy
and this is what is usually perceived as shortness of breath
(physiological dysnoea) by women.(not RR rise ).
 Also there is an increase in the oxygen availability to the
tissues and placenta or baby.

9. Endocrine system
 Progesterone: increases throughout preg. Secretion in first
5 weeks by corpous lutum and then by the placenta till
delivery where it drops.
 It causes smooth muscle relaxation in gut ( heart burn)
ureters and renal pelvis ( leading to dilatation and
increased urination and risk of urinary tract infection)
vessels (decreasing resistance and contributing to the
headache mechanism as well as the rise in temperature
that happens for pregnant women).
 Oesterogen: it rises during preg. The same as progesterone
in secretion.
 It increasese Breast and nipple growth, and pigmentation
of the areola. Promote uterine blood flow, and myometrial
growth, cervical softening. Also it Increases Sensitivity and
expression of myometrial oxytocin receptors. And it
increases Water retention and protein synthesis.

11.  Human placental lactogen: basically it modifies
maternal metabolism to increase the energy supply to
the fetus by increasing insulin secretion, but decreases
insulin’s peripheral effect (liberating maternal fatty
acids and sparing glucose enabling it to be diverted to
the fetus).
 Progesterone and cortisol also decreases Insulin’s
peripheral effect i.e increasing insulin resistance.

12.  Glands that is important in pregnancy:
 The Pituitary gland: it increases in size during preg. Mainly
the anterior lobe ( which secretes FSH, LH, GH and
Prolactin)( the posterior lobe sceretes Oxytocin and ADH).
 Prolactin increases during pregnancy to combine force
with oestrogen in growing the breast ducts and promoting
milk production.
 Oxytocin increases substantially in the first stage of labour
to contract the uterus and in the puerperium during
suckling to eject the milk for the baby.
 It is very important to know that the blood supply to this
gland does not change despite the change in size that is
why if PPH happens a necrosis of the gland happens and so
failure of its function (Sheehan syndrome).

14. Sheehan syndrome
where there is fine wrinkling of face, loss of eyebrows laterally, and skin
hypopigmentation. The MRI shows the gland filled with cerebrospinal
fluid.

15.  The Thyroid gland: it enlarges due to the increased
demands during preg.
 The iodine uptake increases, T3 and T4 (thyroxine)
both rises eraly in preg. Then fall out to reach the non
preg. Level in late preg. TSH remain within normal
range. That is why symptoms of hyper and
hypothyroidism can happen during preg.
 What is the benefits ? (Grave’s disease where
antibodies can cross the placenta and cause fetal
harm).

17. Questions please?
 References for the presentation?
 Obstetrics by Ten Teachers 19th edition.
 Oxford handbook of Obstertics & Gynaenecology 3rd
edition.
Another advisable book
Training in Obstetrics and Gynecology the essential
curriculum. Oxford press.