Physiological changes in pregnancy

1. ANATOMICAL CHANGES
2. PHYSIOLOGICAL CHANGES
3. BIOCHEMICAL CHANGES

ANATOMICAL CHANGES
 GENITAL
 BREAST
 SKIN
 SKELETON
 EYES

GENITAL CHANGES
 UTERUS
Musles of Uterus
In pregnancy muscles undergo both
HYPERTROPHY and HYPERPLASIA.
Fundus > Body
Outer Longitudinal layer
Intermediate Layer
Inner Circular Layer
12
WEEKS
PronouncedUpto:

NON PREGNANT UTERUS
60 grams
Cavity: 5-10 ml
Length: 7.5 cm
Arterial supply: Uterine
Artery
PREGNANT UTERUS
900-1000 grams
Cavity: 1000 ml
Length: 35 cm
Capacity: 500-1000 times
Arterial supply: Uterine Artery
and Ovarian Artery

Shape of Uterus:
NON
PREGNANT:
PYRIFORM
12 Weeks:
GLOBULAR
28 Weeks:
PYRIFORM
36 Weeks:
GLOBULAR

Genital changes
- Uterine ligaments: Hypertrophy
Dextro-rotation of Uterus:
the uterus is tilted and twisted to the right in 80%
of cases
Levorotation of Cervix
- Uterine Peritonium: Deepening of the pouch of Doughlas
- Lower uterine segment (LUS)
the LUS is formed from the isthmus
formed from the 4th month to reach 10 cm at full term

 BRAXTON HICKS CONTRACTION:
 Irregular
 Infrequent
 Spasmodic
 Painless
 Without any effect on dilation of cervix
 Intra uterine pressure < 8 mmHg
 Detected bimanually by 2nd trimester.
 Intensity- 5-25 mmHg
Not Seen in ABDOMINAL PREGNANCY.

Uterine Vessels
 At 20 weeks diameter became twice thus causing
increase blood flow.
 Spiral artery loose contractibility
 Estrogen stimulation
 17β estradiol cause:
 Increase uterine
artery vasodilation
 Decrease uterine
vascular resistance

Genital changes
• The cervix
• Changes seen after 1 month of pregnancy.
- edema and congestion, and becomes soft
- Hypertrophy and hyperplasia of cervical gland
- mucus plug (operculum): cervical mucus closing the cervical
canal
- act as immunoglobulin barrier to protect uterine content
against infection
- increased secretion from its glands

• The vulva
shows increased vascularity and
varicosities
Labia minora: pigmented & hypertrophied.
Fallopian tube:
Hypertrophy.
Flattened epithelium.
Torsion

Genital changes
• The vagina
- shows increased vascularity soft, moist and bluish
- distention of vagina at birth
pH- 3.5-6
• The ovary
shows increased vascularity and size
one ovary contains the corpus luteum
Extrauterine decidual reaction beneath
the surface.
• Pelvic ligaments
- relaxation of the ligaments
- relaxation of the pelvic joints
- the pelvis become more mobile and increases in capacity
JACQUEMIER’S SIGN

Breasts: increase in circulation
 Engorgement and venous prominence
 Mastodynia (breast ternderness): tingling to frank
pain caused by hormonal responses of the mammary
ducts and alveolar system
 Montgomery’s tubercles: enlargement of
circumlacteal sebaceous glands of the areola
 Colostrum secretion: can be sqweezed out at
about 12 weeks.
 By 16 weeks become thick and YELLOWISH.

Montgomery tubercles
non pigmented nodules
(12-20) around the areola
in 2nd month (enlarged
sebaceous glands or
rudimentary lactiferous
ducts).

Skin changes• Pigmentation
due to increased melanocyte stimulating hormone:
- linea nigra: pigmentation of the linea alba, more marked below
the umbilicus
- chloasma gravidarum: Butterfly pigmentation of the face (mask
of pregnancy)
• Striae gravidarum
- stretch of the abdominal wall
rupture of the subcutaneous elastic fibers
pink lines in flanks
- become white after labor

Skeletal changes
• Increased lumbar
lordosis
• Relaxation of pelvic
joints and
ligaments due to
progesterone and
relaxin

EYES
 Increased vitreous outflow Decrease in Intraocular
pressure
 Corneal sensitivity is decreased
 Increase in corneal thickness thus may have difficulty with
previously comfortable contact lenses.
 Brownish-red opacities on the posterior surface of the
cornea—Krukenberg spindles—have also been observed
 Increased pigmentation
 Transient loss of accommodation
 Visual function is unaffected

Weight increase
•There is an increase
weight of approximately
12.5 Kg at term.
•The main increase
occurs in the 2nd half of
the pregnancy, 0.5
Kg/week
1st Trimester 2nd Trimester 3rd Trimester
1 kg 5 kg 5 kg

PHYSIOLOGICAL CHANGES
 CARDIOVASCULAR
 HEMATOLOGICAL
 RESPIRATORY
 RENAL
 NERVOUS
 GASTROINTESTINAL

 Position and size of heart:
 Due to elevation of diaphragm heart moves to left and upward, apex
shifted laterally.
 Chest X-ray changes:
 Larger cardiac silhouette with horizontal positioning.
 Staightening of left upper cardiac border.
 Small benign pericardial effusion
 ECG changes
 Increased heart rate (+15%) i.e Sinus
tachycardia
 15-degree left axis deviation i.e
QRS deviation.
 Lead III: small Q wave & inverted
P wave.
 V1 and V2: Increase R/S ratio

 ECHOCARDIOGRAM CHANGES:
 Slightly increased End diastolic and
End systolic volume.
 Slightly improved LV function.
 Slightly increased venticular
dimension with
Spherical left ventricular
remodelling.
 Small pericardial effusion.
 Increased tricuspid annulus
diameter.
 Physiological tricuspid
regurgitation.
 No change in septal thickness or
ejection fraction

HEART SOUNDS:
 Apex beat shifted to 4th intercostal space, 2.5 cm lateral to
midclavicular line.
 SYSTOLIC MURMER: Apical or pulmonary area: Due to
decreased blood viscosity & torsion of great vessels.
 MAMMARY MURMER:
Continous hissing murmer at tricuspid area i.e left 2nd & 3rd
ICS due to increased blood flow
through internal mammary vessels.
 S3 or THIRD HEART SOUND:
due to rapid diastolic filling.

Cardiovascular changes (cont)
 Stroke volume +30%
 Heart rate +15%
 Cardiac output +40%
 Oxygen consumption +20%
 SVR (systemic vascular resistance) -5%
 Systolic BP -10mmHg
 Diastolic BP -15mmHg
 Mean BP -15mmHg

 SUPINE HYPOTENSION SYNDROME:
During pregnancy, cardiac output is
very sensitive to positional
alterations. In the supine position,
the inferior vena cava is compressed
by the enlarged uterus, resulting in
decreased cardiac output.
Although most women do not
become overtly hypotensive when
lying supine due to opening of
collateral circulation
In some cases (10%) may have
symptoms that include dizziness,
light-headedness, tachycardia and
syncope.
Cardiac output increases 1.2L/min
i.E 20% when woman moves from
Supine to left lateral position.

 Unchanged in the upper body
 Significantly increases in the lower extremities,
esp. during supine, sitting or standing position,
returns to near normal in lateral recumbent position
Venous pressure: Venous blood flow

HEMATOLOGICAL CHANGES
 Blood volume +30%
 Plasma volume +40%
 Red blood cell volume +20%
 Dilusional anemia
 Increase cardiac output
 Decrease blood viscosity
 Vasodilatation


Haematological changes
• Circulating red cell mass increases by 20-
30%
( rises more in multiple pregnancies and iron
supplement)
• Serum iron concentration falls
absorption from gut and iron-binding
capacity rise
• Plasma folate concentration halves by term
( due to increased renal clearance)
red cell folate concentration falls less
• Mild maternal anaemia associated with
increased placental/birthweight ratio
decreased birthweight

Haematological changes
• Erythropoietin rises especially if iron supplement not taken
• Human placental lactogen may stimulate haematopoiesis
• Fall in packed cell volume from 36% in early pregnancy to 32% in the 3rd
trimester ( normal plasma volume expansion)
• WBC count rises ( increase in polymorphonuclear leucocytes)
• Neutrophil number rises with oestrogen
peak at 33 weeks
stabilizing after that
until labour and the puerperium, when they rise sharply
Platelet count and platelet volume are largely unchanged

Iron metabolism
 Only 10% of ingested iron is absorbed.
 Total iron requirement in pregnancy is 1000 mg.
 Iron loss in menstrual bleeding is 30mg/ cycle.
 Thus saving of 300mg of iron due to 10 months of
amenorrhea.
 Iron requirement mostly increased in 3rd trimester.
 Daily iron requirement to compensate the avg daily loss:
Fetus & placenta
300 mg
Expanded RBC mass
400 mg
Obligatory loss
200 mg
Non menstruating woman 1 mg
In 2nd half of pregnancy 6-7 mg

Plasma protein changes
Parameter Nonpregnant Pregnancy near
term
Change
Total proteins (g) 180ased 230 Increased
Plasma protein
conc.
(g/100 ml)
7 6 Decreased
Albumin
(g/100 ml)
4.3 3 Decreased
( 30%)
Globulin
(g/100 ml)
2.7 3 Increased
Albumin:
Globulin
1.7: 1 1: 1 Decreased

IMMUOLOGICAL FUNCTION:
 Early pregnancy: Proinflammmatory
 Mid Pregnancy: Anti inflammatory
 Parturition: Recrudencence of an inflammatory process
 Suppresion of T-helper (Th 1) and T-cytotoxic 1 cells leads to:
 Decrease secretion of interleukin-2 (IL-2), interferone γ
and TNF-β
 Pregnancy related remission of autoimmune diseases.
 Failure of Th1 supression leads to pre-eclampsia
development.
 Upgradation of Th2 cells: Increased production of IL-4, IL-6 &
IL-13
 10 times increase in interleukin 1β in cervical and vaginal mucus
in 1st trimester.
• T and B lymphocyte counts do not change but their function is
suppressed ( women become more susceptible to viral
infections, malaria and leprosy)

Pulmonary changes
 Mucosal hyperemia
 Subcostal angle
 Chest circumference and
diameter
 Diaphragmatic excursion
 Tidal volume : +30-40%
 PO2 is increased, PCO2 is
decreased.
 Total lung capacity decrease by
15%
 Minute ventilation
+30-40%
 Mild respiratory alkalosis

• Increased salivation (ptyalism)
• Taste is often altered very early in pregnancy
• Increase appetite & thirst: frequent small snacks are adviced
• Gums: Hyperemic, softens and bleeds easily.
Localised vascular swelling known as Eppulis of Pregnancy
• Heart burn (reflux oesophagitis) due to relaxation of the cardiac sphincter due to
progesterone and relaxin
• Emesis gravidarum, morning sickness in 50 %
• Decreased gastric acidity, which interfere with iron absorption
• Constipation
reduced gut motility due to progesterone
increased water and salt absorption
• Hemorrhoids due to elevated venous pressure due compression by gravid uterus.

• Liver
- Hepatic synthesis of albumin, plasma globulin and fibrinogen increases
- Total hepatic synthesis of globulin increases stimulated by estrogen
- Hepatic arterial and portal venous flow increases.
- Total serum Alkaline phosphatase activity almost doubles:
mostly due to Heat stable placental Alkaline phosphatase isoenzymes
• Gallbladder
Gall bladder increases in size and empties more slowly
Progesterone potentially impairs gallbladder contraction by
inhibiting cholecystokinin-mediated smooth muscle stimulation,
which is the primary regulator of gallbladder contraction
Relaxation of gall bladder increases the tendency of stone
formation
Cholestasis is almost physiological
Secretion of bile is unchanged

Urinary changes
• Kidneys
- 1.5 cm increase in size
- hydronephrosis
- increase in GFR
 25% by 2nd week
 50% by 2nd trimester
- 80% increase in effective renal plasma flow before the end of 1st
trimester.
Renal Function Test:
Decrease serum creatinine level (Even >0.9mg/dl considered abnormal)
30% higher creatnine clearance.
Glucosuria.
Protenuria—
non pregnant woman- > 150 mg/dl
pregnant woman- >300 mg/dl

Relaxin
Endothelin and NO production
•Renal vasodilation
• Renal afferent and efferent arteriolar
resistance
Renal blood flow.
GFR
Urinary
Frequency

 URETER:
 BLADDER:
•Dilatation of the ureters due to compression.
•Unequal dilation due to cushoning effect of sigmoid colon on left
and dextro-rotation of uterus.
•Atony of the ureteric muscles caused by progesterone and relaxin
causing hydro-ureter
• Vesico-ureteric reflux increased due to pressure of the uterus on
the ureter
Changes in the ureter in pregnancy leads to urinary stasis
and pyelitis
HYPERPLASIA of bladder muscles elevates the Trigone
Cause thickening of its posterior or intraureteric margins
Deepening and widening of the trigone.

 PITUITARY GLAND:
 Enlarge by 135 percent.
 Primarily due to estrogen-stimulated hypertrophy and
hyperplasia of lactotropes.
 Gonadotrophes decline in number.
 Corticotrophes and thyrotropes remain constant.
 Somatotrophes are suppressed.
 Growth Hormon:
 17 weeks: placenta is the main source of secretion.
 Maternal serum values increases from 3.5 ng/ml at 10
wks to 14 ng/mi at 28 wks
 Placental GH differs from pituitary GH by 13 aminoacid
–secreted by syncytiotrophoblast in nonpulsatile
fashion.

Thyroid Gland
 Hyperplasia and slight generalised enlargement of
gland.
 Maternal serum iodine level fall due to increased renal
loss and transplacental shift to fetus.
 Iodine intake increased from 100-150 µgm/day to 200
µg/day
 Rise in BMR due to increased maternal and fetal
oxygen need.
 Increased serum protein bound iodine and thyroxine
bound globulin due to estrogen stimulation.
 Total T3, T4 increased but fT3, fT4 and TSH remain
same.

Contd….
 Level of calcitonin increased by 20%.
 Since increase in TBG is dependent on estrogen, a
failure of the PBI to rise indicate fetal compromise.
 Adrenal cortex – slight enlargement of adrenal
cortex (thickness of zona fasciculata increased).
 Significant increase in aldosterone,
deoxycorticosterone (DOC), corticosteroid binding
globulin, cortisol and free cortisol.
 Hypercortisolism occurs due to increased plasma
cortisol half life, delayed plasma clearance

Changes of endocrine glands
Gland Morphological Physiological
Pituitary Increase in weight by 30-
50%. Twice in size
GH, Prolactin, ACTH, CRH
Normal – TSH
Gonadotrophin
Thyroid Hyperplasia BMR, TBG, Total T3,T4
Normal – fT3, fT4, TSH
Maternal Serum Iodine
Adrenal Cortex Minimal enlargement Aldosterone,
DOC(deoxycorticosterone), CBG,
Corisol, Free Cortisol
Parathyroid Hyperplasia Normal PTH – does not cross placenta
Pancreas Hyperinsulinism in 3rd Trimester. Anti
insulin factors and insulin resistance
modify action of insulin during
pregnancy

Metabolic changes
 By 3rd trimester BMR increased by 10-20%.
 Additional increase of 10%in twins
 Total Energy Demand: 77,000 kcal
85 kcal/day. 285 kcal/day. 475 kcal/day
Water metabolism:
• Increased water retention i.e minimum 6.5 L extra.
• Fall in plasma osmomolality by 10 mOsm/kg.
• cause pitting edema of ankles and legs.
•

Metabolic changes• Carbohydrate metabolism
- pregnancy is hyperlipidaemic and glucosuric
- after mid-pregnancy, resistance of insulin develops
- plasma glucose concentrations rise, maintained between 4.5-5.5 mmol/L
- glucose crosses the placenta, the fetus uses glucose as primary energy
substrate, transport occurs by carrier mediated mechanism
- the insulin resistance is endocrine-driven, via increase in cortisol and hPL
- concentrations of glucagons and the catecholamines are unaltered

Metabolic changes
• Carbohydrate metabolism
- carbohydrate deposited in the liver as glycogen
- some escapes to general circulation
- portion metabolised by the tissues:
converted to depot fat
stored as muscle glycogen
- first noticeable change occurs in blood sugar
- tested by giving a load of oral glucose (glucose tolerance test)
- the blood sugar, after meal, remains high facilitating placental
transfer

Metabolic changes
• Carbohydrate metabolism
- with increased placental production of steroid, less glycogen
deposited in liver and muscles
- the effect of fasting is pronounced in pregnancy
overnight fast of 12hrs
hypoglycaemia, production of ketone bodies

Metabolic changes
• Protein metabolism
- positive nitrogen balance
additional 1000 gm protein added
feotus and placenta- 500 gm
Uterus and breast- 500 gm
- on average 500 g of protein retained by the end of pregnancy
- blood and urine urea are reduced

• Fat metabolism
- by 30 weeks, 4Kg are stored in form of
depot fat in the abdominal wall, back and thights
modest amount in breasts

Metabolic changes
Electrolyte and mineral metabolism:
 1000 mEq of Sodium and 300 mEq of Potassium
retained.
 But serum conc. Decreased due to plasma volume.
 Excreation remain unchanged.
 Total serum Calcium declined bt S. ionized calcium
remain unchanged.
 Serum Magnesium level declined.
 Serum Phosphate remain unchanged
 Iodine requirement increased
 Increased maternal T4 production.
 Incresed demand by feotus.
 50% increased glomerular filtration rate increased.

Acid–Base Equilibrium The increased respiratory effort during pregnancy, and in turn the
reduction in Pco2, is likely induced in large part by progesterone which
acts centrally and lowers the threshold and increases the sensitivity of the
chemoreflex response to CO2.
Compensating resp. alkalosis
Plasma bicarbonate level
decreases to 22
pH
Shift Oxygen dissociation curve to LEFT.
affinity of maternal
Hb for oxygen,
oxygen releasing capacity
BOHR
EFFECT
2-3, DPG Shift the curve back to RIGHT.
pCO2 from maternal blood
CO2 transfer from fetus to mother

Physiological changes in pregnancy

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Physiological changes in pregnancy