Physiological changes in 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