Physiological changes of pregnancy involve changes to support fetal growth. The uterus expands greatly to accommodate the fetus. Other anatomical changes include increased blood volume, softening of ligaments, and breast enlargement. Metabolic changes store fat and protein for the fetus. Cardiovascular changes increase blood volume, cardiac output, and blood pressure. Respiratory changes elevate the diaphragm and increase ventilation. Renal changes increase creatinine clearance. Hormonal changes, like increased progesterone and estrogen, induce these anatomical, metabolic, and physiological adaptations in the mother.

1. Physiological changes of pregnancy
Dr Bellington Vwalika
Obstetrician and
Gynaecologist

2. ‘pregnancy is a normal physiological
process’
 Profound changes are produced in the
genital tract and general of the mother and
in the function of most organs and systems of
the body
 These anatomical ,endocrinological and
physiological changes are a positive
adaptation of the mother to accommodate
and support the fetus as it grows and
develop through out the pregnancy

3.  These changes are a temporary adaptation
and produce no permanent deleterious
effects in the mother

4. Anatomical
changes
 Genital organs
– Vulva oedematous and hyperaemic;varicosities
– Vagina hypertrophic ,oedematous and vascular
– Vagina and supporting strutures become
progressively distensible
– Secretion –copius,acidic PH 3.5-6 by action of
Doderlein’s bacilli
 Ovary –ovulation and development of corpus
luteum

5.  Uterus
– Changes from non pregnant weight of 50g to
1000g., expands from an organ of
approx.7.5cm×2.5cm with a capacity of 4mls to
28×24×21cm with a capacity of 4L at term.Total
blood flow increases from 50mls/min at 10 weeks
to 500-700mls/min at term
– Enlargement due to hypertrophy and hyperplasia,
and elongation

6. – 3 distinct muscle layers are identifiable
 Outer longitudinal with hood like arrangement over the
fundus ,some fibres continuos with round ligament
 Inner circular and have like action around tubal orifices
and internal os
 Intermediate –thickest and strongest in criss-cross
fashion through which blood vessels run.Give figure of 8
.At contraction occlude blood vessels.Living ligature

7. – Rotates to the right as it grows due the recto
sigmoid on the left
 Increased sodium retention due to
oestrogen, increased aldosterone and
ADH.This leads to retention of 6.5 litres of
water

8. General structural changes
 Skin- pigmentation increases particulary of
the nipples ,umbilicus,vulva and midline linea
nigra.Chloasma of pregnancy –face .Striae
gravidarum –rapid and excessive stretching
of skin accompanied by breaking of
underlying connective tissue

9. General structural changes
 Pelvic ligaments-fibrocartilage becomes
softer and loose, synovial fluid increases –
considerable increase in mobility of sacroiliac
and sacrococygeal joints
 Breasts- nipples become large ,more
pigmented and erectile. After the second
month, breasts progressively increase in size

10. Metabolism
 CHO-Weight gain normal of 12 kg(25% of
non pregnant value), 2kg in first trimester
and 5kg in second and third trimester.This is
equal to 0.5kg per week
– Total nutritional calorie requirement for whole
pregn is 3600kj/day-met out of average normal
diet-supplements only necessary if total calories
intake <1200kj/day.calcium and iron may need
supplementation

11. Metabolism
 Protein-overall picture is one of positive
nitrogen balance.Peak values reached at 28
weeks and by end of pregnany 500g retained
 Fat-main form of maternal stored energy. 4kg
stored by 30 weeks –mostly as depot fat in
abd wall, back and thighs and perhaps
retroperitoneally. Blood fat increases from 3rd
month –total lipid at term is 1050g/dl(700g/dl
non pregnant)

12. Cardiovascular changes
 Haematological changes –occur by 8th week
– Blood volume increases 30% maximally at 30-32/40
– Plasma volume- 40%
– RBC volume -18-20%
– Advantages of haemodilution
 Reduced viscosity ensures optimal gaseous exchange
between mother and fetus
 Protection against effects of blood loss at delivery

13. – Increase CO by 40-50%(3.5l/min to 6.0L/min)
– Increase in stroke volume and heart rate
– Bp reaches a nidir at 16 to 20 weeks gestation
then increases
– 1st heart sound is amplified

14.  Neutrophilic leucocytosis( from 7000 to 10-
15,000/cu.mm) due to an increase of mature and
immature neutrophils
 Total protein increases from 180 gm to 230gm
 Blood coagulation factors-fibrinogen is raised by
50% from 200-400mg% to 300-600mg%.Platelets
increase through out the pregnancy
– Fibrinolytic activity is depressed until 15 minutes after
delivery

15. Coagulation changes
 Pregnancy activates the clotting system
 All factors except XI and XIII go up
 Most significant increases seen with factors
VII,VIII and fibrinogen

16. Heart and circularion
 Due to elevation of diaphragm ,rotates to the
left
 Apex beat to 4th space
 Increase in cardiac output of 40% with peak
at 30-32/40
 BP remains normal due to decreased
peripheral resistance

17.  Uterine,pulmonary,renal and cutaneous
blood flow increases
 Metabolic
– BMR is increased-30%
– CHO absorption increases-diabetogenic state
– Glycosuria in 1/3 due to
 Low renal threshold(normal 180mg%)
 Increased GFR and low tubular reabsorption
 Due rapid absorption of CHO from the gut

18.  Respiratory system-elevation of diaphragm,upward
flaring of the ribcage,increased costal movement and
dyspnoea
– Breathing becomes diaphramatic
– Hyperventillation leading to increased tidal volume (28% at
term)and respiratory minute volume by 40%, RR inreases
9%-leads to respiratory alkalosis
– Physiological dead space decreases

19. Renal changes
 Urinary under relaxing effect of progesterone
 Kidney volume,weight and size increase
 24 hour creatinine clearance increase 40-
50%
 Tubular absorption of glucose decrease
 Mild alkalaemia-pH 7.42-7.44 units

20. Gastro-intestinal changes
 The main change is one of decreased
motility which is due to the increased
circulating progesterone
 The growth of the conceptus and uterus
leads to increases in appetite and thirst
 In late pregnancy ,pressure of large uterus
reduces capacity for large meals leading to
ingestion of frequent small snacks

21. Endocrine changes
 Progesterone
 Estrogen
 Cortisol,pituitary hormones
 Insulin,relaxin
 Aldosterone
 Thyroid hormones
 Human chorionic gonadotrophin(HCG)
 Human placental lactogen(HPL)