Physiological Changes During Pregnancy in the each trimester in the detail way

1. Physiological Changes
During Pregnancy
Krishnakumar.D
Assistant professor

2. Introduction
• During pregnancy there is progressive anatomical, physiological
and biochemical change not only confined to the genital organs
but also to all systems of the body.
• This is principally a phenomenon of maternal adaptation to the
increasing demands of the growing fetus.

3. 1) GENITAL ORGANS
2) BREASTS
3) CUTANEOUS CHANGES
4) WEIGHT GAIN
5) BODY WATER METABOLISM
6) HEMATOLOGICAL CHANGES
7) CARDIOVASCULAR SYSTEM
8) METABOLIC CHANGES
9) SYSTEMIC CHANGES

4. GENITAL ORGANS

5. GENITAL ORGANS
VULVA:
• Vulva becomes edematous and more vascular.
• Superficial varicosities ( multiparae).
• Labia minora ( pigmented and hypertrophied).
VAGINA:
• Vaginal walls becomes hypertrophied, edematous and more
vascular.
• Increased blood supply of the venous plexus surrounding the
walls gives the bluish coloration of the mucosa (Jacquemier’s
sign).
• The length of the anterior vaginal wall is increased.

6. Secretion:
• The secretion becomes copious, thin and curdy white, due to
marked exfoliated cells and bacteria.
• The pH becomes acidic (3.5–6) due to more conversion of
glycogen into lactic acid by the Lactobacillus acidophilus
consequent on high estrogen level.
• The acidic pH prevents multiplication of pathogenic organisms.
Cytology:
• There is preponderance of navicular cells in cluster and plenty of
lactobacillus.

7. UTERUS
• There is enormous growth of the uterus during pregnancy.
• The uterus which in nonpregnant state weighs about 60 gm,
cavity of 5–10 mL and measures about 7.5 cm in length.
• At term, weighs 900–1000 g and measures 35 cm in length.
• The capacity is increased by 500–1000 times.
• Changes occur in all the parts of the uterus—body, isthmus and
cervix.

8. BODY OF THE UTERUS:
• There is increase in growth and enlargement of the body of the
uterus.
Enlargement:
• The enlargement of the uterus is affected by the following
factors:
Changes in the muscles
• (1) Hypertrophy and hyperplasia (New muscle fibers – estrogen
& progesterone – up to 12week).
• (2) Stretching (beyond 20weeks – wall become thinner at term –
1.5cm ).

9. Arrangement of the muscle fibers:
Three distinct layers of muscle fibers
are evident:
• (1) Outer longitudinal (continuous
– round ligaments).
• (2) Inner circular (scanty –
sphincter like arrangement).
• (3) Intermediate (thickest &
strongest – crisscross).

10. • Apposition of two double curve
muscle fibers give the figure of ‘8’
form.
• Thus, when the muscles contract,
they occlude the blood vessels
running through the fibers and
hence called living ligature.

11. Vascular system
• Nonpregnant state – blood supply to the uterus is mainly
through the uterine and least through the ovarian.
• Pregnant state, the latter carries as much the blood as the
former.
• There is marked spiralling of the arteries, reaching the maximum
at 20 weeks; thereafter, they straighten out.

12. • Doppler velocimetry has shown uterine artery diameter
becomes double and blood flow increases by eight fold at 20
weeks of pregnancy.
• This vasodilatation is mainly due to estradiol and progesterone.

13. • Veins become dilated and are valveless.
• Numerous lymphatic channels open up.
• The vascular changes are most pronounced at the placental site.
• The uterine enlargement is not a symmetrical one.
• The fundus enlarges more than the body.

14. Weight:
• The increase in weight is due to the
increased growth of the uterine
muscles, connective tissues and
vascular channels.
Relation:
• Shape—Nonpregnant pyriform shape is
maintained in early months.
• It becomes globular at 12 weeks.
• As the uterus enlarges, the shape once
more becomes pyriform or ovoid by 28
weeks and changes to spherical beyond
36th week.

15. Position:
• Normal anteverted position is exaggerated upto 8 weeks.
• Thus, the enlarged uterus may lie on the bladder rendering it
incapable of filling, clinically evident by frequency of micturition.
• Multiparae with lax abdominal wall, there is a tendency of
anteversion.
• Primigravidae with good tone of the abdominal muscles, it is
held firmly against the maternal spine.

16. Lateral obliquity:
• As the uterus enlarges to occupy the abdominal cavity, it usually
rotates on its long axis to the right (dextrorotation).
• This is due to the occupation of the rectosigmoid in the left
posterior quadrant of the pelvis.
• This makes the anterior surface of the uterus to turn to the right
and brings the left cornu closer to the abdominal wall.
• The cervix, as a result, is deviated to the left side (levorotation)
bringing it closer to the ureter.

17. Contractions (Braxton-Hicks):
• During pregnancy, uterus undergoes spontaneous contraction.
• This can be felt during bimanual palpation in early weeks or
during abdominal palpation.
• The contractions are irregular, infrequent, spasmodic and
painless without any effect on dilatation of the cervix.
• The patient is not conscious about the contractions.

18. Braxton-Hicks
• Near term, the contractions become frequent with increase in
intensity so as to produce some discomfort to the patient.
• Ultimately, it merges with the painful uterine contractions of
labor.
• In abdominal pregnancy, Braxton-Hicks contraction is not felt.

19. • During contraction there is complete closure of the uterine veins
with partial occlusion of the arteries in relation to intervillous
space resulting in stagnation of blood in the space.
• This diminishes the placental perfusion, causing transient fetal
hypoxia which leads to fetal bradycardia coinciding with the
contraction.

20. ISTHMUS
• During the first trimester, isthmus hypertrophies and elongates
to about 3 times its original length.
• It becomes softer.

21. CERVIX
Stroma:
• There is hypertrophy and hyperplasia of the elastic and connective
tissues.
• Fluids accumulate inside and in between the fibers.
• Vascularity is increased specially beneath the squamous epithelium
of the portio vaginalis which is responsible for its bluish coloration.
• Chadwick’s Sign.
• Goodell’s Sign.
• Mucus Plug.

22. Epithelium:
• There is marked proliferation of the endocervical mucosa with
downward extension beyond the squamocolumnar junction.
• This gives rise to clinical appearance of ectopy (erosion) cervix.

23. • Sometimes, the squamous cells also become hyperactive and
the mucosal changes simulate basal cell hyperplasia or cervical
intraepithelial neoplasia (CIN).
• These changes are hormone induced (estrogen) and regress
spontaneously after delivery.

24. Secretion:
• The secretion is copious and tenacious-physiological leucorrhea
of pregnancy.
• This mucous is rich in immunoglobulins and cytokines.
• The mucus not only fills up the glands but forms a thick plug
effectively sealing the cervical canal.
• Microscopic examination shows fragmentation or
crystallization (beading) due to progesterone effect.

25. Anatomical:
• The length of the cervix remains unaltered but becomes bulky.
• The cervix is directed posteriorly but after the engagement of
the head, directed in line of vagina.
• There is no alteration in the relation of the cervix.
• Variable amount of effacement is noticed near term in
primigravidae.
• In multiparae, the canal is slighly dilated.

26. FALLOPIAN TUBE:
• The total length is somewhat increased.
• The tube becomes congested.
• Muscles undergo hypertrophy.

27. OVARY:
• The growth and function of the corpus luteum reaches its
maximum at 8th week when it measures about 2.5 cm and
becomes cystic.
• It looks bright orange, later on becomes yellow and finally pale.
• Regression occurs following decline in the secretion of human
chorionic gonadotropin (hCG) from the placenta.

28. • Hormones-estrogen and progesterone secreted by the corpus
luteum maintain the environment for the growing ovum before
the action is taken over by the placenta.
• These hormones not only control the formation and maintenance
of decidua of pregnancy, but also inhibit ripening of the follicles.
• Thus both the ovarian and uterine cycles of the normal
menstruation remain suspended.

29. Decidual reaction:
• There may be patchy sheet of decidual cells on the outer
surface of the ovary.
• These are metaplastic changes due to high hormonal
stimulation.

30. BREASTS

31. SIZE:
• Increased size of the breasts becomes evident even in early
weeks.
• There is also hypertrophy of the connective tissue stroma.
• Myoepithelial cells become prominent.
• Vascularity is increased which results in appearance of bluish
veins running under the skin.
• “Axillary tail” (prolongation of the breast tissue under cover
of the pectoralis major) – becomes enlarged and painful.

32. NIPPLES AND AREOLA:
• The nipples become larger, erectile and deeply pigmented.
• Variable number of sebaceous glands (5–15) which remain
invisible in the nonpregnant state in the areola, become
hypertrophied and are called Montgomery’s tubercles.
• Those are placed surrounding the nipples.
• Their secretion keeps the nipple and the areola moist and
healthy.
• An outer zone of less marked and irregular pigmented area
appears in second trimester and is called secondary areola.

33. SECRETION:
• Secretion (colostrum) can be squeezed out of the breast at
about 12th week which at first becomes sticky.
• Later on, by 16th week, it becomes thick and yellowish.

34. CUTANEOUS CHANGES

35. CUTANEOUS CHANGES
PIGMENTATION-
Face (chloasma gravidarum or pregnancy mask):
• It is an extreme form of pigmentation around the cheek, forehead
and around the eyes. It may be patchy or diffuse; disappears
spontaneously after delivery.
Abdomen:
• Linea nigra.
• Striae gravidarum.
• Striae albicans.

36. Linea nigra:
• It is a brownish black
pigmented area in the midline
stretching from the
xiphisternum to the symphysis
pubis.
Striae gravidarum:
• These are slightly depressed
linear marks with varying
length and breadth found in
pregnancy.
• They are predominantly found
in the abdominal wall below
the umbilicus, sometimes over
the thighs and breasts.

37. Striae albicans:
• These stretch marks represent the scar tissues in the deeper
layer of the cutis. Initially, these are pinkish but after the
delivery, the scar tissues contract and obliterate the
capillaries and they become glistening white in appearance
and are called Striae albicans

38. OTHER CUTANEOUS CHANGES:
• These include vascular spider and palmar erythema which are due
to high estrogen level.
• Mild degrees of hirsutism may be observed and in puerperium the
excess hair is lost.

39. WEIGHT GAIN

40. WEIGHT GAIN
• The total weight gain during the course of a singleton
pregnancy for a healthy woman averages 11 kg (24 lb)
• This has been distributed to 1 kg in first trimester and 5 kg each
in second and third trimester.
• The total weight gain at term is distributed approximately as
follows:

41. During pregnancy, there is variable amount of retention of
electrolytes:
• Sodium (1000 mEq), Potassium (10 g) and Chlorides.
• The sodium is osmotically active and partially controls the
distribution of water in various compartments of the body.
Causes of increased sodium retention during pregnancy are:
(1) increased estrogen and progesterone
(2) increased aldosterone consequent on the activation of the
renin-angiotensin system .
(3) due to increased antidiuretic hormone.
• The amount of water retained during pregnancy at term is 6.5
liters.

42. The increased accumulation of fluid in the tissue spaces
mainly below the uterus is due to:
• (1) diminished colloid osmotic tension due to hemodilution
driving the fluid out of the vessels and
• (2) increased venous pressure of the inferior extremities.

43. Importance of weight checking:
• Rapid gain in weight of more than 0.5 kg (1 lb) a week or more
than 2 kg (5 lb) a month in later months of pregnancy may be the
early manifestation of pre-eclampsia and need for careful
supervision.
• Stationary or falling weight may suggest intrauterine growth
retardation or intrauterine death of fetus.

44. BODY WATER METABOLISM

45. BODY WATER METABOLISM
• The amount of water retained at term is about 6.5 liters.
• The water content of the fetus, placenta and amniotic fluid is
about 3.5 liters.
• Pregnancy is a state of hypervolemia.
• There is active retention of sodium (900 mEq), potassium (300
mEq) and water.

46. Theimportantcausesof sodiumretentionand
volumeoverload are:
• Changes in osmoregulation
• Increased estrogen and progesterone
• Increase in reninangiotensin activity
• Increased aldosterone, deoxycorticosterone
Increase in water intake due to lowered osmotic threshold
for thirst causes polyuria in early pregnancy.

47. HEMATOLOGICAL CHANGES

48. HEMATOLOGICAL CHANGES
• BOOD VOLUME
• PLASMA VOLUME
• RBC AND HEMOGLOBIN
• LEUKOCYTES and IMMUNE SYSTEM
• TOTAL PROTEIN
• BLOOD COAGULATION FACTORS

49. BLOOD VOLUME
• During pregnancy there is increased vascularity of the enlarging
uterus with the interposition of uteroplacental circulation.
• The activities of all the systems are increased.
• Blood volume is markedly raised during pregnancy.
• All the constituents of blood are affected with increased blood volume.
• The blood volume starts to increase from about 6th week, expands
rapidly thereafter to maximum 40–50% above the nonpregnant level
at 30–32 weeks.
• The level remains almost static till term.

51. PLASMA VOLUME
• It starts to increase by 6 weeks and it plateaus at 30 weeks of
gestation.
• The rate of increase almost parallels to that of blood volume but
the maximum is reached to the extent of 50%.
• Total plasma volume increases to the extent of 1.25 liters.
• The increase is greater in multigravida, in multiple pregnancy
and with large baby.

52. RBC AND HEMOGLOBIN
• The RBC mass is increased to the extent of 20–30%.
• The total increase in volume is about 350 mL.
• This increase is regulated by the increased demand of oxygen transport
during pregnancy.
• RBC mass begins to increase at about 10 weeks and continue till term
without plateauing.
• Iron supplementation increases the RBC mass by 30%.
• Reticulocyte count increases by 2%.
• Erythropoietin level is raised.

53. • The disproportionate increase in plasma and RBC volume
produces a state of hemodilution (fall in hematocrit) during
pregnancy.
The advantages of relative hemodilution are:
(1) Diminished blood viscosity ensures optimum gaseous
exchange between the maternal and fetal circulation.
This is facilitated by lowered oxygen affinity of maternal red
cells observed in later half of pregnancy.
(2) It protects the woman against the adverse effects of supine
and erect posture.
(3) Protection of the mother against the adverse effects of blood
loss during delivery

54. LEUKOCYTESand IMMUNE SYSTEM
• Neutrophilic leucocytosis occurs to the extent of 8000/mm3
and even to 20,000/cu.mm in labor.
• The increase may be due to rise in the levels of estrogen and
cortisol.

55. TOTAL PROTEIN
• Total plasma protein increases from the normal 180 g
(nonpregnant) to 230 g at term.

56. BLOOD COAGULATIONFACTORS
• Pregnancy is a hypercoagulable state.
• Fibrinogen level is raised by 50% from 200–400 mg/dL in
nonpregnant to 300–600 mg/dL in pregnancy.
• As a result
• Erythrocyte sedimentation rate (ESR) gives a much higher value
(four fold increase) during pregnancy.
• Gestational thrombocytopenia may be due to increased platelet
consumption.

58. To be continued…

59. CARDIOVASCULAR SYSTEM

60. CARDIOVASCULAR SYSTEM
ANATOMICAL CHANGES:
• Due to elevation of the diaphragm consequent to the
enlarged uterus, the heart is pushed upwards and outwards
with slight rotation to left.

62. Abnormal clinical findings
• The apex beat is shifted to the 4th intercostal space about 2.5
cm outside the midclavicular line.
• A systolic murmur may be audible in the apical or pulmonary
area.
• This is due to decreased blood viscosity and torsion of the great
vessels.
• A continuous hissing murmur (audible over the tricuspid area in
the left second and third intercostal spaces called the
“mammary murmur”).

63. • Doppler echocardiography shows an increase in the left
ventricular end diastolic diameters.
• ECG reveals normal pattern except evidences of left axis
deviation.

64. CARDIAC OUTPUT
• The cardiac output (CO) starts to increase from 5th week of
pregnancy, reaches its peak 40–50% at about 30–34 weeks.
• CO is lowest in the sitting or supine position and highest in the
right or left lateral or knee chest position.
• Cardiac output increases further during labor (+50%) and
immediately following delivery (+70%).
• MAP also rises.

65. The increase in CO is caused by:
• Increased blood volume
• To meet the additional O2 required due to increased metabolic
activity during pregnancy.

66. BLOOD PRESSURE
• Systemic vascular resistance (SVR) decreases (–21%) due to the
smooth muscle relaxing.
• Inspite of the large increase in cardiac output, the maternal BP
(BP = CO × SVR) is decreased due to decrease in SVR.
• There is overall decrease in diastolic blood pressure (BP) and
mean arterial pressure (MAP) by 5–10 mm Hg.

67. VENOUS PRESSURE
• Antecubital venous pressure remains unaffected.
• Femoral venous pressure is markedly raised specially in the later
months.
• The femoral venous pressure is raised from 8–10 cm of water in
nonpregnant state to about 25 cm of water during pregnancy in lying
down position and to about 80–100 cm of water in standing position.
• This explains the fact that the physiological edema of pregnancy
subsides by rest alone.
• Distensibility of the veins and stagnation of blood in the venous
system explain the development of edema, varicose veins, piles and
deep vein thrombosis.

68. CENTRAL HEMODYNAMICS
• No significant change in CVP, MAP and PCWP though there is
increase in blood volume, cardiac output and heart rate.
The reasons are:
• There is significant fall in SVR, pulmonary vascular resistance (PVR)
and colloidal osmotic pressure.

69. SUPINEHYPOTENSIONSYNDROME
(POSTURALHYPOTENSION)
• The gravid uterus produces a compression effect on the inferior
vena cava when the patient is in supine position.
• This results in production of hypotension, tachycardia and
syncope.
• The normal blood pressure is quickly restored by turning the
patient to lateral position.

70. REGIONALDISTRIBUTIONOF BLOOD FLOW:
• Uterine blood flow is increased from 50 mL/min in non-pregnant
state to about 750 mL near term.
• The increase is due to the combined effect of uteroplacental and
fetoplacental vasodilatation.

71. • Pulmonary blood flow (normal 6000 mL/min) is increased by 2500
mL/min.
• Renal blood flow (normal 800 mL) increases by 400 mL/min.
• The blood flow through the skin and mucous membranes reaches
a maximum of 500 mL/min by 36th week.
• Heat sensation, sweating or stuffy nose complained by the
pregnant women can be explained by the increased blood flow.

72. METABOLIC CHANGES

73. METABOLIC CHANGES
• GENERAL METABOLIC CHANGES
• PROTEIN METABOLISM
• CARBOHYDRATE METABOLISM
• FAT METABOLISM
• LIPID METABOLISM
• IRON METABOLISM

74. GENERAL METABOLIC CHANGES
• Total metabolism is increased due to the needs of the growing
fetus and the uterus.
• Basal metabolic rate is increased to the extent of 30% higher
than that of the average for the nonpregnant women.

75. PROTEIN METABOLISM
• There is a positive nitrogenous balance throughout pregnancy.
• At term, the fetus and the placenta contain about 500 gm of
protein and the maternal gain is also about 500 gm chiefly
distributed in the uterus, breasts and the maternal blood.
• Amino acids are actively transported across the placenta to the
fetus.

76. CARBOHYDRATE METABOLISM
• Transfer of increased amount of glucose from mother to the fetus
is needed throughout pregnancy.
• Insulin secretion is increased.
• Plasma insulin level is increased due to a number of contrainsulin
factors.

77. • Increased insulin level favors lipogenesis (fat storage).
• During maternal fasting, there is hypoglycemia, hypoinsulinemia,
hyperlipidemia and hyperketonemia.
• Lipolysis generates fatty acids for gluconeogenesis and fuel supply.
• Plasma glucagon level remains unchanged.

78. FAT METABOLISM
• An average of 3–4 kg of fat is stored during pregnancy mostly in
the abdominal wall, breasts, hips and thighs.
• Plasma lipids and lipoproteins increase appreciably during the
later half of pregnancy due to increased estrogen,
progesterone, hPL and leptin levels.

79. LIPID METABOLISM
• HDL level increases by 15%.
• LDL is utilized for placental steroid synthesis.

80. IRON METABOLISM
• Iron is absorbed in ferrous form duodenum and jejunum and is
released into the circulation as transferrin.
• About 10% of ingested iron is absorbed.
• Iron is transported actively across the placenta to the fetus.
• Total iron requirement during pregnancy is estimated
approximately 1000 mg.

81. • In the absence of iron supplementation, there is drop in
hemoglobin, serum iron and serum ferritin concentration at
term pregnancy
• Thus pregnancy is an inevitable iron deficiency state.

82. SYSTEMIC CHANGES

83. SYSTEMIC SYSTEM
• RESPIRATORY SYSTEM
Acid base balance
The pH rises
• URINARY SYSTEM
Kidney
Ureter
Bladder
• ALIMENTARY SYSTEM
• LIVER AND GALLBLADDER
• NERVOUS SYSTEM
• CALCIUM METABOLISM AND LOCOMOTOR SYSTEM

84. RESPIRATORY SYSTEM
• There is elevation of the diaphragm by 4 cm.
• Total lung capacity is reduced by 5% due to this elevation.
• Total pulmonary resistance is reduced due to progesterone
effect.
• The subcostal angle increases from 68° to 103°, the transverse
diameter of the chest expands by 2 cm and the chest
circumference increases by 5–7 cm.
• A state of hyperventilation occurs during pregnancy leading to
increase in tidal volume.

86. Acid base balance
• The hyperventilation causes changes in the acid base balance.
• The arterial PaCO2 falls from 38–32 mm Hg and PaO2 rises from
95–105 mm Hg.
• These facilitate transfer of CO2 from the fetus to the mother and
O2 from the mother to the fetus.

88. The pH rises
• The pH rises in order of 0.02 unit and there is a base excess of
2 mEq/L.
• Thus, pregnancy is in a state of respiratory alkalosis.
• Maternal O2 consumption is increased by 20–40% due to
increased demand of the fetus, placenta and maternal tissues.

89. URINARY SYSTEM
Kidney
• There is dilatation of the ureter, renal pelvis and the calyces.
• The kidneys enlarge in length by 1 cm.
• Renal plasma flow is increased by 50–75%.
• Glomerular filtration rate (GFR) is increased by 50%.
• Increased GFR causes reduction in maternal plasma levels of
creatinine, blood urea nitrogen (BUN) and uric acid.

90. Ureter:
• Ureters become atonic due to high progesterone level.
• Dilatation of the ureter above the pelvic brim with stasis is marked
on the right side specially in primigravidae. It is due to
dextrorotation.
• The stasis is marked between 20–24 weeks.

91. Bladder:
• There is hyper-trophy of the muscles and elastic tissues of the
wall.
• In late pregnancy, the bladder mucosa becomes edematous due
to venous and lymphatic obstruction especially in primigravidae
following early engagement.
• Increased frequency of micturition is noticed at 6–8 weeks of
pregnancy which subsides after 12 weeks.
• Stress incontinence may be observed in late pregnancy due to
urethral sphincter weakness.

92. ALIMENTARY SYSTEM
• The gums become conge-sted and spongy and may bleed to
touch.
• Muscle tone and motility are diminished.
• Cardiac sphincter is relaxed and regurgitation of acid gastric
content into the esophagus (chemical esophagitis and heart
burn).
• Diminished gastric secretion and delayed emptying time of
the stomach.
• Atonicity of the gut leads to constipation.

93. LIVER AND GALLBLADDER
• No histological change in the liver cells, but the functions are
depressed.
• There is mild cholestasis (estrogen effect).
• Marked atonicity of the gallbladder (progesterone effect)

94. NERVOUS SYSTEM
• Temperamental changes are found during pregnancy and in the
puerperium.
• Nausea, vomiting, mental irritability and sleeplessness are
probably due to some psychological background.
• Postpartum blues, depression or psychosis may develop in a
susceptible individual.

95. NERVOUS SYSTEM
• Carpal tunnel syndrome may appear in the later months of
pregnancy.
• Similarly paresthesia and sensory loss over the anterolateral
aspect of the thigh may occur. It is due to compression of the
lateral cutaneous nerve of the thigh.

96. CALCIUMMETABOLISMANDLOCOMOTORSYSTEM
• There is increase in the demand of calcium by the growing
fetus to the extent of 28 g, 80% of which is required in the last
trimester.
• Daily requirement of calcium during pregnancy and lactation
averages 1–1.5 g.
• Maternal total calcium levels fall but serum ionized calcium
level is unchanged.

97. • There is increased mobility of the pelvic joints due to softening
of the ligaments caused mainly by hormone.
• This along with increased lumbar lordosis during later months of
pregnancy due to enlarged uterus produces backache and
waddling gait.

98. Thank You