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Physiological Changes During Pregnancy

Neelam Maurya

Physiological Changes During Pregnancy In Reproductive System 1. Female Reproductive System, Pregnancy And Childbirth - Anatomy Human Charts

Physiological Changes During Pregnancy

GENITAL ORGANS:

The body of the uterus-

  • Hyperplasia
  • Height increases (7.5 cm to 35cm)
  • Weight increases (50g to 1000g )
  • Uterine ligaments →hypertrophy
  • Dextrarotated uterus→tilted and twisted to the right (80%)
  • Lower uterine segment :Formed from isthmus (4th month to 10 cm )

Cervix 

  • Edema and congestion, and becomes soft 
  • Mucus plug (operculum): cervical mucus closing the cervical canal 
  • Increased secretion from glands
  • The vulva shows increased vascularity and varicosities

Vagina 

  • Increased vascularity soft, moist and bluish 
  • Distention at birth

Ovary 

  • Increased vascularity and size 
  •  Pelvic ligaments – relaxation
  • Relaxation of pelvic joints 
  • Pelvis become more mobile and increases in capacity

Breast changes

  • Increased size and vascularity 
  • Warm, tense and tender
  • Increased pigmentation of nipple and areola
  • Secondary areola appear 
  • Montgomery tubercules appear on the areola
  • Colostrum like fluid is expressed at the end of the 3rd month 

WEIGHT INCREASE:

Reproductive Weight Gain(6Kg)

Net Maternal Weight Gain(6kg)
Fetus  3.3 kg Increased blood volume 1.3 kg
Placenta 0.6 kg
Liquor  0.8 kg
Uterus 0.9 kg  Increased ECF 1.2 kg
Breasts  0.4 kg
Fat & protein 3.5 kg

 URINARY CHANGES:

Kidneys

  • Increase in size 
  • Hydronephrosis 
  • Increased GFR
  • Dilatation of the ureters 
  • Atony of the ureteric muscles 
  • Hydro-ureter
  • Vesico-ureteric reflux increased 
  • Pressure of the uterus on the ureter affects more the right ureter due to the dextro-rotation of the uterus
  • Changes in the ureter in pregnancy leads to urinary stasis and pyelitis
  • Frequency of micturation causes
  • 1st trimester: pressure of the uterus on the bladder 
  • Late in pregnancy: engagement of the head

Urinary output 

  • Increase in tubular reabsorption:Na retention↑, Serum K↓
  • Reabsorption of glucose↑
  • Creatinine  & Urea ↓
  • Extracellular water is increased  due to increased amounts of aldosterone progesterone and oestrogen

GASTROINTESTINAL CHANGES:

  • Ptyalism
  • Taste altered 
  • Increase appetite & thirst
  • Heart burn
  • Emesis gravidarum
  • Decreased gastric acidity(interferes with iron absorption)
  • Constipation 
  •  Liver 
  • ↑ Synthesis of albumin, plasma globulin and fibrinogen  
  • Gall bladder
  • Increases in size and Slow empting
  • Cholestasis

CARDIOVASCULAR CHANGES:

PARAMETERS CHANGES

Cardiac output
(L/min)

 ↑ by 40% (maximum at 30th week)

Stroke volume
(mL)

 ↑ by 27%

Heart rate
(per minute)

 ↑ by17%
Blood pressure

Unaffected or mid-pregnancy drop of
diastolic pressure by 5–10 mm Hg

Venous
pressure

 ↑ 100%

Colloid oncotic
pressure
(mm Hg)

 ↓ by 14%

Systemic
vascular
resistance
(SVR)

 ↓ by  21%

Pulmonary
vascular
reistance (PVR)

  ↓ by 34%

Total extracellular volume

  ↑ by 16%
  • Shift of apical impulse laterally and upwards in the left 4’h intercostal space 

RESPIRATORY CHANGES:

PARAMETERS CHANGES

Respiration
rate/min

 Unaffected

Vital capacity
(mL)

 Unaltered

Tidal volume(ml)

 ↑ by 40%

Residual
volume (mL)

 ↓ by 20%

Inspiratory
capacity (IC)

 ↑ by  10%

Minute
ventilation

 ↑ by 40%

Total lung
capacity (mL)

 ↓ by 5%

ACID-BASE CHANGES:

PARAMETERS CHANGES

Arterial PO2

 ↑(106 mm Hg)

Arterial PCO2

 Diminished(32 mm Hg)

pH

 ↑ (7.42)

Plasma HCO3–

 ↓ (22 mmol/L)
  • Respiratory alkalosis:Rightward shift of the maternal oxyhaemoglobin dissociation curve ( due to an increase in 2,3-DPG in erythrocytes)
  • Oxygen unloading to the fetus which has:  marked leftward shift of the oxyhaemoglobin dissociation curve, (due to lower sensitivity of fetal haemoglobin to 2,3-DPG)

HEMATOLOGICAL CHANGES:

PARAMETERS CHANGES

Blood volume (mL)

 ↑ by 1500 (30–40%)

Plasma volume (mL)

 ↑ by 1250(40–50%)

Red Cell volume (mL)

 ↑ by 350(20–30%)

Total Hb (g)

 ↑ by 85 (18–20%)

Serum Iron

 ↓

TIBC

 ↑

Hematocrit

 Diminished

Erythropoietin 

 ↑

WBC count

 ↑(Neutrophilic leukocytosis-8,000  to 20,000/mm3)

 Platelet count and volume 

 unchanged

Coagulation factors

 VII, VIII , X,plasma fibrinogen: ↑
Antithrombin III , XI, XIII: ↓
ESR ↑
Plasma fibrinolytic activity  ↓
Plasma Protein Concentration ↓(Albumin↓30%; Globulin↑; A:G ↓)

 ENDOCRINAL CHANGES:

GLAND/HORMONE SIZE/LEVEL ACTIVITY

 Anterior pituitary

 ↑ ↑

Prolactin 

 ↑ in pregnancy &↓ in lactation ↑

Posterior pituitary

 – Releases oxytocin on the onset of labor

Insulin

 ↑  ↑ Resistance 

TSH

 ↓ in 1 & 2 but, ↑ in 3 trimester –

Thyroid 

 ↑  ↑ 

T3, T4

 ↑ in Total(↓T4/T3 free) Thyroid binding globulin doubles

 Parathyroid 

 ↑ ↑ to regulate calcium metabolism

Adrenals 

 ↑ ↑

Progesterone 

 ↑ upto 250mg/day
  • ↓colon activity,
  • Nausea,Constipation,
  • ↓bladder and ureteric tone,
  • ↓ Diastolic pressure,
  • ↓venous dilatation,
  • ↑Temperature

Oestrogens 

 ↑ upto 30-40mg/day(85%)
  • Control growth & function of uterus
  • Development of breasts
  • Alter connective tissue constituents
  • Water retention
  • Reduce sodium excretion

 Placental hormones( secreted by the syncytiotrophoblast of the chorion &decidual cells) include: 

  • Chorionic gonadotropin
  • Chorionic thyrotropin
  • Chorionic corticotropin
  • Estrogens
  • Progesterone
  • Prolactin
  • Placental lactogen 

METABOLIC CHANGES:

  • Increased BMR

Carbohydrate metabolism :

  • Hyperlipidaemic and glucosuric
  • ↑ Resistance of insulin
  • ↑ Plasma glucose concentrations
  • First noticeable change in blood sugar :Tested by glucose tolerance test
  • With increased placental production of steroid, less glycogen deposited in liver and muscles 

Protein metabolism 

  • Positive nitrogen balance
  • Blood and urine urea are reduced

Fat metabolism

  • By 30 weeks→4Kg stored as depot fat in the abdominal wall, back ,thighs & breasts
Exam Question
 
  • Respiratory alkalosis  is seen during pregnancy
  • Decreased peripheral vascular resistance in pregnancy
  • ↑ed cardiac output, &  tidal volume is seen during pregnancy
  • Shift of apical impulse laterally and upwards in left 4th intercostal space is physiological in last trimester of pregnancy seen during pregnancy 
  • Fall in serum iron concentration,Increase in serum iron binding capacity & Increase in blood oxygen carrying capacity are  seen during pregnancy
  • Globulin,  Fibrinogen & Leukocytes are  increased in pregnancy
  • Sodium retention occurs in pregnancy
  • Sr. potassium is decreased in pregnancy 
  • Increased BMR is seen in  pregnancy 
  • Insulin resistance in pregnancy is because of Human placental lactogen & Progesterone
  • During pregnancy the maternal blood volume increases by  50%
  • Vital capacity remains unaltered in pregnancy
  • Fibrinogen level increases  in pregnancy
  • Maximum increase in cardiac output occurs by  30th week
  • Net weight gain in pregnancy is 24 lb or 12 kg
  • In pregnancy Increased MCV & glomerular flow
  • Fall in free T4/T3 in 3rd trimester
  • TSH falls in the first and second trimester but increases in the third trimester
  • There is an increase in Thyroid binding globulin
  • Decrease in Urea , Creatinine & Reabsorption of glucose
  • Tidal volume and resting minute ventilation increase during late trimester
  • Functional residual capacity and the residual volume are decreased
  • Total pulmonary resistance reduced
  • Systemic vascular resistance  is decreased during third trimester of a normal pregnancy
  • Chorionic gonadotropin, Chorionic thyrotropin & Chorionic corticotropin are placental hormones
  • Factor XIII reduction is consistent with normal pregnancy
  • Decline of 5-10 mm of Hg is seen in in diastolic blood pressure in pregnancy 
  • Prolactin is Highest during pregnancy and fall during lactation
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