physiological effects on different systems of body during pregnancy

3. Shifa Riaz

4. Factors responsible for physiological changes
• hormonal changes in collagen and involuntary muscles
• increased blood volume with increase blood flow to uterus and
kidneys
• growth of fetus resulting in enlargement and displacement of uterus
• increase in body weight and adaptive changes in posture and centre
of gravity

5. 1: endocrine system
Three hormones are most
important to consider during
pregnancy.
• progesterone
• estrogen
• relaxin

6. progesterone
• Progesterone is produced first by the corpus leteum and then by the
placenta.
• At 10 weeks of pregnancy corpus leuteum releases 30mg of
progesterone per 24 hours.
• At 20 weeks of pregnancy placenta releases 75mg of progesterone
per 24 hours
• At 40 weeks of pregnancy placenta releases 250-300mg of
progesterone per 24 hours.
• 3 major progestogens are released by the placenta and the major one
is progesterone.

7. effects of progesterone
• Reduction in smooth muscle tone
a) stomach ( delayed emptying, reduced peristalsis )
b) colon ( increased absorption of water causes constipation )
c) uterine muscle tone is reduced
d) ureters distends and accomodate urine which causes urinary tract
infections
e) bladder tone reduces ( detrusor muscles)
f) urethtral tone reduced and causes stress incontinence
g) reduced tone in smooth muscles of blood vessels wall causes
decrease in diastolic pressure

8. cont...
• increase in temperature ( 0.5 to 1 degree )
• hyperventilation; reduction in alveolar and arterial pco2
• increased storage of fat
• development of the breast and milk producing ducts

9. estrogen
• estrogen is produced by corpus leuteum and then from placenta
• At 20 weeks placenta releases 5mg of estrogen per 24 hours
• At 40 weeks placenta releases 50mg of estrogen per 24 hours
• major estrogen is estriol which is produced in considerable amount
also excreted in urine
• formerly, it was used to diagnose the normal pregnancy. Now
ultrasound is used for this purpose
• estrogen is also produced by maternal and feotal adrenal glands and
from feotal liver

10. effects of estrogen
• increases growth of uterus and breast ducts
• increases level of prolactin in order to prepare the breasts for
lactation; estrogens may assist in maternal calcium metabolism
• may prime receptor sites for relaxin ( pelvic joints, joint capsules,
cervix )
• increases water retention
• higher levels result in increase in glycogen level, predisposing to
thrush

11. relaxin
• in early stages, produced by theca and leutinized granulosa cells of
corpus leuteum
• in later stages , produced by decidua cells
• it is produced as early as 2 weeks of gestation, is at its highest levels
in the first trimester and then drops by 20% to remain steady.

12. effects of relaxin
• pelvic floor muscles relaxation
• mammary growth
• relaxation of uterus; remarkable ability of uterus to distend and in the
production of necessary important addisional connective tissue
structures for support
• inhibition of myometrial contractions for upto 28 weeks ( 7 months )
when women become aware of Braxton Hicks contractions
• softening of collagenous content of the cervix
• gradual replacement of collagen in target tissues ( pelvic girdle, joint
capsules, cervix ) collagen synthesis is more than degradation and
there is increased water content, so there is an increase in volume.

13. Other hormonal changes
• pituiatry gland increases in size by 30-50%
• prolactin increases
• cortisol increases
• aldosterone increases
• insulin receptor cells increases
• islets of langerhans increases
• beta cells increases
• prostacyclin increases
• peripheral tissue resistance increases
• lactotropes increases
• erythropoetin increases initially then falls in third trimester
• catecholamine level decreases from ist to third trimester
• free T3 and T4 remain same
• glucose in urine remains normal
• HCG may supress TSH

14. 2: Reproductive system
effects:
• Amenorrhea is the first sign of pregnancy, although it is not
uncommon to experiance a slight bleed, for 1-2 days.
• cervix, if viewed with the speculum will be seen to have changed in
color from pink to a bluish shade ( Chadwick’s sign)
• in the final weeks softening, dilatation, and distensibility of the cervix
occurs which is collectively called ripening of cervix
• Hypertrophied and softening of cervix is called Godell’s sign.
• As pregnancy progresses a plug of thick mucous forms in the cervical
canal, sealing the uterus.
• At about 12 weeks ( 3 months ) growing uterus rises out of the pelvis
to become an abdominal organ.

15. cont..
• In primgravida, fundal height drops in the final 2-3 weeks because the feotal
head enters the pelvic inlet. This head will be said to be “ engaged “. This may
cause an increase in the frequency of micturation.
• In multigravidae, foetal head may not engage until labour begins.
• At the end of pregnancy abdominal palpation is used to determine how much
of the fetal remains above the pelvic brim. This is estimated in fifth month.
• size of uterus increases from about 50g to 1000g
• muscle fibers also increase in length and thickness throughout the pregnancy
• collagenous tissue also increases; thus elasticity increases
• In nulliparous woman the uterus would hold about a quarter of teaspoon of
fluid, whereas the gravid uterus contains 10 pints of fluid.

16. Braxton Hicks contractions
• bursts of irregular, short, usually painless contractions are called braxton hicks
contractions.
• They facilititate the blood flow from placental side and play a part in development of
lower uterine segment.
Labour:
bursts of regular and painfull contractions are called labour
prelabour/ false labour:
contractions of variable length ( 20seconds to 4minutes ), intensity of which may or may
not be painful. More common in multigravid woman.

17. 3: Cardiovascular System
effects:
• blood volume increases by 40% and returns to normal after 6-8 weeks after delivery.
• plasma volume increases by 45% thus causes fall in hemoglobin levels by 80% ( ist
trimester: normal hb is 11 but in remaining trimesters normal hb is 10.5 ). This effect is
called dilutional or physiological anemia.
• Heart increases in size and accomodates more blood, so the stroke volume rises by 30%
and cardiac output increases by 30-50% or 60%.
• blood pressure falls in pregnancy, so woman may easily feel faint from prolonged
standing.
• In the 3rd trimester weight of the fetus may compress aorta and inferior vena cava
against the lumbar spine when the woman is lying supine, causing dizziness and even
unconsciousness called PREGNANCY HYPOTENSIVE SYNDROME ( imp SEQ ) The
infallible remedy is to turn the woman on to her left side.

18. cont.. Peripheral
• Progesterone acts on smooth muscles to produce slight hypotonia
and increase in temperature, that is why pregnant woman generally
has good peripheral circulation and does not feel cold.
• Due to increase in peripheral circulation mucous membranes become
more active, this can result in symptoms such as
nasal stuffiness
increased vaginal discharge
prolongations of cough and colds
nasal bleeds and vaginal thrush

19. cont..
• vascular hypotonia, downward pressure of enlarging fetus,
progesterone and relaxin mediated changes in collagen all predispose
to VERICOSE VEINS and GRAVITATIONAL EDEMA.
• Heart rate usually increases 10-20bpm
• RBCs increases by 20%
• intravascular volume increases to 1500ml
• clotting factors increases
• antithrombin III, fibrinolytic activity and platelet count decreases
• Greatest increase in CARDIAC OUTPUT ( 60% ) occurs after delivery (
imp MCQ )

20. 4: Respirtory system
effects
• Increased circulating progesterone level sensitize the respiratory centre in the medulla to carbon
dioxide, thus increases demand for oxygen; hyperventilation.
• breathing rate increases 15 to 18 breaths per minute
• tidal volume increases by 40%
• alveolar ventilation increases
• expiratory reserve volume is reduced
• oxygen increases by 15- 20%
• uper respiratory hypersecretion also occurs
• subcostal angle increases
• anteroposterior and transverse diameter increases by 2cm ( 1in )
• Total chest circumference increases by 5-7cm ( 1.5in )
• lower costal girth is increased by 115 cm
• In the 3rd trimester, enlarging uterus displace diaphragm upwards for about 4cm or more
• upward pressure of fetus also affects the ribs causing them to flare

21. cont..
• respiratory excursion is limited at the lung bases and greater in the
mid-costal and apical regions, that is why women experience
considerable breathlessness on even modest exertion at the end of
the pregnancy.
• Relaxin hormone softens the costochondral junctions and renders
them more mobile. Women complain of costal marging pain or rib
ache, and of fetus kicking the diaphragm or ribs.

22. 5: Breasts
• At 2-4 weeks of pregnancy:
Tenderness, tingling, enlargement of breast occur. Breast becomes nodular and
lumpy. Progesterone ( duct system ) and Estrogen ( alveolar system ) are
responsible for growth of breasts.
Increase of breast weight : 400 to 800g
There is increase in blood supply and number, size and complexity of ducts.
At 8 weeks of pregnancy
• sebaceous glands in the pigmented area around nipples become more active ,
appearing as nodules called MONTOGOMERY’S TUBERCLES.
• sebum assists the nipple to become softer and pliable.

23. At 12 weeks of pregnancy:
• The nipples and the area around them become more pigmented and remian
so for as much as 12 months after parturition.
• This pigmentation occurs due to melanin production by anterior pituitary.
At 16 weeks of pregnancy:
• colostrum is released by the nipples.
• Human milk comes in about 3rd or 4th postpartum day.
• Nipple stimulation results in release of oxytocin from posterior pituitary.

24. 6: Skin
1. Pigmentation occurs in pregnant woman that causes darkening of the skin
of vulva, nipples, face, blochtes on the forehead and cheeks; known as
chloasma or mask of pregnancy.
• pigmentation related dark line also forms in the skin overlying linea alba.
2. Striae or stretch marks can develop over buttocks,abdomen,breasts and may
become pigmented.
• These striae are consequence of rupture of dermis; overlying epidermis is
stretched and resulting scar is therefore permanent and visible.
• Causes of striae:
 weight gain
hormonally mediated collagen softening
stretching of skin

25. 3. There is increase in blood flow to the skin , which increases the
activity of sebaceous and sweat glands; thus increases evaporation.
pregnant woman is expected to drink more to compensate.
4. Fat is laid down particularly in the 2nd and 3rd trimesters on the
thighs
upper arms
abdomen
buttocks

26. 7: Gastrointestinal system
• Nausea and vomiting occurs due to HCG hormone ( imp MCQ )
• It can be aggravated by certain food odours, iron tablets
• Hyperemesis gravidarum is the condition of excessive vomiting that
can lead towards
maternal dehydration
malnutrition
weight loss
fetal growth retardation
fetal anomilies

27. • Progesterone causes delayed stomach emptying and increase water
absorption
• constipation and heart burn are the usual symptoms of progesterone.
• salivation may be increased.
• softening of the gums occur.
• energy expenditure increases about 1000kj per day.
• An additional intake of 300 calories per day ( imp MCQ )is needed to
meet the basic metabolic demands.
• In pregnant women normal fasting blood glucose levels are lower
than in non pregnant women.
• Average weight gain is between 10-12kg or 25 to 35lb ( imp mcq )
• in first 20 weeks: 2kg
• 20 weeks onwards: 0.5 kg

28. • Average weight gain distribution:
breasts: 0.5kg
placenta: 0.6kg
amniotic fluid: 0.8kg
uterus: 0.9kg
extracellular fluid and blood volume: 1.2kg
fetus: 3.3kg
fat deposits: 4kg

29. 8: Nervous system
• Mood lability, anxiety, depression, insomnia, nightmares, reduction in
memory, amnesia and reduction in brain size all occur in pregnancy.
• water retention ( due to estrogen ) causes pressure on certain nerves
passing from inelastic material like bone and fibrous tissues;resulting
neuropraxia ( carpal tunnel syndrome )

30. 9: urinary system
• HCG in urine early in pregnancy forms the basis of pregnancy test which
declines after 12 weeks of pregnancy. ( imp MCQ )
• blood supply of urinary tact increases in order to remove waste of fetus.
• size and weight of kidneys increase (1cm or 0.5inch).
a) ureters distends and accomodate urine which causes urinary tract infections
and also cause vesicouretral reflux.
b) bladder tone reduces ( detrusor muscles) bladder changes position to
become intra abdominal organ. Urethrovesical angle may be altered.
c) urethtral tone reduced and causes stress incontinence. Delivery can cause
the urethral closure mechanism and be a cause of pudendal nerve damage.

31. 10: musculoskeletal system
connective tissue and joint:
• increases joint laxity, and so in joint range.
• estrogens, progesterone, relaxin and cortisol are responsible for this.
• greater increase in joint range and laxity occurs in second pregnancy than ist.
Abdominal muscles:
• abdominal muscles, particularly both sides of rectus, as well as linea alba
become stretched to the point of their elastic limit.
• This sigficantly decreases the efficiency of muscle contraction.
• Shift in center of gravity as the baby grows also decreases the mechanical
advantage of abdominal muscles.

32. Pelvic floor muscles:
• pelvic floor muscles drop as much as 2.5cm as a result of pregnancy.
Pelvis:
• Hormonally influenced increased mobility of joints causes anterior and posterior width of pelvis
to become significantly wider as pregnancy progresses.
SI joint:
• SI joint locking mechanis becomes less efficient
• permits increase movement
Pubic symphysis:
• normal seperation: 4-5mm
• pregnancy: 2-3 mm increases
• last 2 months of pregnancy: average 7.7mm
• pubic symphysis diastasis: more than 10mm
Coccyx:
• Coccyx is exposed to sudden increase in intra pelvic pressure and higher incidence of coccydynia.
• coccyx needs to move in extension.

33. 11: Posture and Balance
• centre of gravity shifts forwards and upwards.
• cervical lordosis.
• chin drops
• rounded shoulders.
• scapular protraction and shoulder internal rotation
• upper cross syndrome ( tightness of pect major and stretch weakness of scapular stabilisers )
• hyperkyphosis
• abdominal muscles stretching
• lumbar lordosis and lumbar extensors tightness
• hip external rotation and abduction
• hip flexors tightness and hip extensors stretch weakness
• genu recurvatum
• eversion, tight tendoachilles, foot arch drop
• wider base of support

34. Physiological changes during trimesters:
Ist trimester 0-12 weeks 2nd trimester 13-26 weeks 3rd trimester 27-40 weeks
Implantation of fertilised ovum in
uterus occurs 7 to 10 days after
fertilization
pregnancy becomes visible to
others
uterus is now large and has regular
contractions
mother is fatigued, urinates
frequently, experiance nausea and
vomiting ( morning sickness )
nausea and vomiting disappear frequent urination,back pain, leg
edema, fatigue, shortness of
breath, and constipation
breast size increases fetus length: 19-23cm
fetus weight: 600g ( 1-2lb)
baby lenth: 33-39cm
baby weight: 3400g ( 7lb )
normal: ( 5 to 10 lb)
weight gain ( 0-3lb ) fetus has now eyebrows, eyelashes
and fingernails
emotional changes occur mother now feels movement of
baby ; 20 weeks
fetus length: 6-7cm
fetus weight: 20g