Physiological changes during pregnancy

D. Kavitha M.Sc(N),M.Sc(Psy),DHHM,BSAM, Ph.D scholar

Lecturer in OG

MTPGRI&HS

Pondicherry

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.

Body system alterations

• Cardiovascular • Hematological• Respiratory• Genitourinary• Gastrointestinal• Immunological• Musculoskeletal• Endocrine

Cardiovascular system

• Cardiovascular adaptation affects all organ systems.

• Cardiovascular anatomy and physiology changes to accommodate increasing maternal and fetal circulatory needs.

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.

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

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

• 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

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.

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.

Respiratory changes

• Anatomic changes:– Diaphragm elevation

– Chest expansion

– Capillary dilation early in pregnancy causes• Engorgement of entire tract from nares to bronchi• Voice changes

Respiratory changes - cont

• Physiological changes:– Increased need for oxygen

– Improved oxygen delivery

– Hyperventilation

– Compensatory respiratory alkalosis

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

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

• 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

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

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

Urinary changes

• Kidneys – increase in size and GFR.

Bladder – tone decreases due to progesterone, becomes displaces as uterus grows.

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.

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

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.

• 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

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

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

• 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

• 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

• 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

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

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.

Musculoskeletal changes

• Increased lumbar lordosis

• Relaxation of pelvic joints and ligaments

due to progesterone and relaxin

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

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

Thank

You