Physiological changes during pregnancy allow the mother's body to support fetal growth and development. The cardiovascular, respiratory, gastrointestinal, urinary, and endocrine systems undergo remodeling. The cardiovascular system increases blood volume and cardiac output by 40% by the third trimester. Respiration increases to meet higher oxygen needs. Hormonal changes, like increased progesterone and estrogen, prepare the uterus and breasts for birth. Overall, the adaptations sustain a healthy environment for the fetus throughout pregnancy.

1. Physiological changes
during pregnancy
D. Kavitha M.Sc(N),M.Sc(Psy),DHHM,BSAM, Ph.D
scholar
Lecturer in OG
MTPGRI&HS
Pondicherry

2. 2
• Maternal physiologic adjustment to pregnancy are
designed to support the requirements of fetal
homeostasis and growth.
• This is accomplished by remodeling maternal systems:
To deliver energy and growth substrates to the fetus
To remove inappropriate heat and waste products
• Those maternal adaptation maintain a healthy
environment for the fetus.

3. Body system alterations
• Cardiovascular
• Hematological
• Respiratory
• Genitourinary
• Gastrointestinal
• Immunological
• Musculoskeletal
• Endocrine

4. Cardiovascular system
• Cardiovascular adaptation affects all
organ systems.
• Cardiovascular anatomy and physiology
changes to accommodate increasing
maternal and fetal circulatory needs.

5. Heart
• Anatomic changes:
– Heart is enlarged, displaced upward and
rotates to the left.
– PMI (point of maximal impulse) shifts to 4th
intercostal space and closer to the
midclavicular line.

6. Heart sounds and rate
• Audible splitting of S1 and S2; S 3
becomes audible.
• Benign systolic murmurs are common.
• Heart rate increases 15-20 beats as
pregnancy progresses

7. Cardiac output
• Defined as the amount of blood pumped from
the left ventricle into the aorta each minute.
– (heart rate x stroke volume = CO)
• In pregnancy increased by 40% by 36-38 wks.
• Influenced by:
• Blood volume
• Stroke volume
• Heart rate

8. • Labor
TIME FRAME CARDIAC OUTPUT CHANGE
1st Trimester Increased 22% > pre-pregnancy values due to
increased stroke volume
3rd Trimester Increased 30-50% > pre-pregnancy values due
to increased heart rate and stroke
Labour Increased 12%-49% during 1st and 2nd stage
due to shunting of blood from uterus to maternal
circulation with pushing

9. Blood pressure
• Due to decreased systemic vascular
resistance, blood pressure is lower at end
of 1st trimester and throughout 2nd, returning to
baseline in 3rd trimester.
Also affected by renin-angiotensin-aldosterone
system from kidneys.

10. Hematological changes
• Increase in WBCs and RBCs.
• Increase blood volume for uterus, fetus
and increased perfusion of other organs,
especially kidneys.
• Increased plasma volume ratio to RBC
volume leads to hemodilution.

11. Respiratory changes
• Anatomic changes:
– Diaphragm elevation
– Chest expansion
– Capillary dilation early in pregnancy causes
• Engorgement of entire tract from nares to bronchi
• Voice changes

12. Respiratory changes - cont
• Physiological changes:
– Increased need for oxygen
– Improved oxygen delivery
– Hyperventilation
– Compensatory respiratory alkalosis

13. Genital changes
• The body of the uterus
- Height and weight (hyperplasia)
the height increases from 7.5 cm to 35cm
the weight increases from 50g to 1000g at term
- Uterine ligaments
show hypertrophy
- Dextro-rotation
the uterus is tilted and twisted to the right in 80% of cases
- Lower uterine segment (LUS)
the LUS is formed from the isthmus
formed from the 4th month to reach 10 cm at full term

14. Genital changes
• The cervix
- edema and congestion, and becomes soft
- mucus plug (operculum): cervical mucus closing the cervical
canal
- increased secretion from its glands
• The vulva
shows increased vascularity and varicosities

15. • The cervix
- edema and congestion, and becomes soft
- mucus plug (operculum): cervical mucus closing the cervical
canal
- increased secretion from its glands
• The vulva
shows increased vascularity and varicosities

16. Genital changes
• The vagina
- shows increased vascularity soft, moist and bluish
- distention of vagina at birth
• The ovary
shows increased vascularity and size
one ovary contains the corpus luteum
• Pelvic ligaments
- relaxation of the ligaments
- relaxation of the pelvic joints
- the pelvis become more mobile and increases in capacity

17. Breast changes
• Increased size and vascularity  warm, tense and tender
• Increased pigmentation of the nipple and areola
• Secondary areola appear
(light pigmentation around the 1ry areola)
• Montgomery tubercules appear on the areola
(dilated sebaceous glands)
• Colostrum like fluid is expressed at the end of the 3rd month

18. Urinary changes
• Kidneys – increase in size and GFR.
Bladder – tone decreases due to
progesterone, becomes displaces as uterus
grows.

19. Urinary changes cont
• Urine flow accumulates and slows.
• Increased renal excretion of BUN, creatinine
and glucose.
• Decreased serum BUN, creatinine and
glucose.
• Decreased tubular reabsorption of glucose.
• Increased tubular reabsoption of sodium.

20. Gastro intestinal changes
• Increased salivation (ptyalism)
• Taste is often altered very early in pregnancy,Increase appetite & thirst
frequent small snacks
• Heart burn (reflux oesophagitis) , 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

21. Gastro intestinal changes
• Esophagus, stomach and intestines move as
uterus grows.
• Round ligament stretches as uterus
expands.
• Gallbladder –decrease tone and motility
combined with increased emptying time can
cause increased risk of gallstones.

22. • Liver
- Hepatic synthesis of albumin, plasma globulin and
fibrinogen increases
- Total hepatic synthesis of globulin increases
stimulated by estrogen
- Hormone-binding globulins rise
- gall bladder increases in size and empties more
slowly
- relaxation of gall bladder increases the tendency of
stone formation
- cholestasis is almost physiological
- secretion of bile is unchanged

23. Hematological changes
• T and B lymphocyte counts do not change but their
function is suppressed
( women become more susceptible to viral infections,
malaria and leprosy)
• Platelet count and platelet volume are largely
unchanged

24. Endocrine changes
• Pituitary
- anterior pituitary increases in size and activity
- posterior pituitary releases oxytocin on the onset of labor
• Thyroid
- increases in size and activity: physiological goiter
- most pregnant women are euthyroid
- thyroid binding globulin concentrations double (not other
thyroid binding proteins)
- total T3, T4 are increased (not the free T3 ,T4)
• Parathyroid
increases in size and activity to regulate calcium metabolism

25. • Adrenals
- increases in size and activity
- total cortisol is increased (free cortisol unchanged)
• Placental hormones
Progesterone
- produced by the corpus luteum
- levels rise steadily during pregnancy, output reaches
250mg/day
- actions:
colon activity reduced, nausea, constipation
reduced bladder and ureteric tone
diastolic pressure reduced, venous dilatation
raises temperature

26. • Placental hormones
Oestrogens
- source:
ovary in early pregnancy
later, oestrone and oestradiol produced by the placenta
increased a hundredfold
oestriol produced by the placenta and fetal adrenals
increased thousand fold
- levels: output of oestrogens reaches a maximum of at least 30-
40mg/day
oestriol accounts 85%
levels increase up to term

27. • Placental hormones
Oestrogens
- possible actions:
1- induce growth of uterus and control its function
2- responsible for the development of breasts ( with
progesterone)
3- alter chemical constitution of connective tissue,
become more pliable
4- cause water retention
5- reduce sodium excretion

28. Metabolic changes
• General metabolism
– increased due to needs of growing fetus
– BMR increased to extent of 30% higher
• Protein metabolism
– Positive nitrogenous balance throughout pregnancy
– Anabolism!
• Carbohydrate metabolism
– Insulin secretion increased
– Sensitivity of insulin receptor reduced
– To ensure continuous supply of glucose to fetus

29. Metabolic changes
• Fat metabolism
– 3-4kg fat stored at abdomen, breast, hips and thighs.
• Lipid metabolism
– HDL level increased by 15%
– LDL utilized for placental steroid synthesis.
• Iron metabolism
– Pregnancy is an iron deficiency state
– Absorption from gut is increased but lost along the routes, to
placenta and during delivery.
– Serum iron and ferritin will fall if supplementation is not given.

30. Musculoskeletal changes
• Increased lumbar lordosis
• Relaxation of pelvic joints and ligaments
due to progesterone and relaxin

32. 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

33. Weight increases
• 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
• Causes:
growth of the conceptus
enlargement of the maternal organs
maternal storage of fat
increase in maternal blood and interstitial fluid