ROBAB DAVAR M.D.

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Anatomical and physiological adaptation to
pregnancy

• ROBAB DAVAR M.D.
• 1387

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Introduction

• The anatomical, physiological, and biochemical
  adaptations to pregnancy are profound.
• Many of these remarkable changes begin soon after
  fertilization and continue throughout gestation,
  and most occur in response to physiological
  stimuli provided by the fetus.

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Mission

• Understanding the adaptations to pregnancy.
• without such knowledge, it is almost impossible
  to understand the disease processes that can
  threaten women during pregnancy and the
  puerperium.

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Anatomical adaptations
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Physiological adaptations
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Anatomical Adaptations
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Uterus
Non Pregnant Uterus Pregnant Uterus
Muscular Structure Almost Solid Relatively thin walled ( 1.5 cm)
weight 70 gm Approx. 1100 gm by the end of pregnancy
Volume 10 mL 5 L by the end of pregnancy
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Mechanism Of Uterine Enlargement

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Uterine size, shape position

• First few weeks, original peer shaped organ
• As pregnancy advances, corpus fundus assumes a
  more globular form.
• By 12 weeks, the uterus becomes almost spherical
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• Subsequently, uterus increases rapidly in length
  than in width assumes an ovoid shape.
• With ascent of uterus from pelvis, it usually
  undergoes Dextrorotation (caused by the
  rectosigmoid colon on the left side).

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Cervix

• As early as 1 month after conception the cervix
  begins to undergo profound softening cyanosis
  due to
• Increased vascularity edema of the entire
  cervix.
• Hypertrophy hyperplasia of the cervical glands.
• Endocervical mucosal cells produce copious
  amounts of a tenacious mucus that obstructs the
  cervical canal soon after conception(mucus plug)

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Cervix

• During pregnancy the basal cells near the
  squamocolumnar junction are likely to be
  prominent in size, shape staining qualities
  (estrogenic effect).
• These changes attribute to the frequency of less
  than optimal pap smears in pregnant women.

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Ovaries

• Cessation of ovulation arrest of maturation of
  new follicles.
• Single corpus luteum of pregnancy is found in
  ovaries of pregnant women that contributes to
  progesterone production maximally during the
  first 6 to 7 weeks of pregnancy (4 to 5 weeks
  postovulation)
• This explains the rapid fall in serum
  progesterone the occurrence of spontaneous
  abortion upon removal of the corpus luteum before
  7 wks.
• Increased diameter of the ovarian vascular
  pedicle from 0.9cm to approx. 2.6 cm at term.

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Relaxin

• Protein hormone with structural features similar
  to insulin insulin like growth factors ?,??.
• Secreted by corpus luteum, decidua placenta in
  a pattern similar to HCG.
• Major biological action is remodeling of the
  connective tissue of reproductive tract, allowing
  accommodation of pregnancy successful
  parturition.
• Also secreted by the heart increased levels
  found in heart failure (Fisher co-workers)

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Fallopian Tubes

• The musculature of the fallopian tubes undergoes
  little hypertrophy.
• The epithelium of the tubal mucosa becomes
  somewhat flattened.

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Vagina Perineum

• Increased vascularity, hyperemia of the skin
  muscles of the perineum vulva.
• Softening of the underlying abundant connective
  tissue.
• Increased vascularity prominently affects the
  vagina resulting in the violet color
  characteristic of chadwick sign.
• Considerable increase in the thickness of the
  vaginal mucosa, loosening of the connective
  tissue, hypertrophy of smooth muscle cells.

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Breast changes
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Physiological Adaptations
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CardioVascular

• Stroke volume
• Heart rate
• SVR
• Systolic BP
• Diastolic BP
• Mean BP
• O2 Consumption

• ( 30)
• ( 15)
• ( 5)
• ( 10 mmHg)
• ( 15 mmHg)
• ( 15 mmHg)
• ( 20)

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CardioVascular
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ECG Changes

• Increased heart rate ( 15)
• 15 left axis deviation.
• Inverted T-wave in lead ???.
• Q in lead ??? AVF
• Unspecific ST changes

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Vascular

• Vascular spider
• Minute, red elevations on the skin
• common on the face, neck, upper chest,
• and arms, with radicles branching out
• from a central lesion. The condition is often
• designated as nevus,angioma, or telangiectasis.
• Palmar erythema
• The two conditions are of no clinical
  significance and disappear in most women shortly
  after pregnancy(estrogen)

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Respiratory
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Pulmonary Function

• The respiratory rate is little changed.
• Tidal volume, minute ventilatory volume, and
  minute oxygen uptake increase significantly as
  pregnancy advances.
• T V by about 40 lead to MVV from 7.25
  liters to 10.5 liters.

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Pulmonary Function

• The functional residual capacity (FRC) and the
  residual volume of air are decreased due to the
  elevated diaphragm.
• Lung compliance remains unaffected.
• Airway conductance is increased and total
  pulmonary resistance is reduced, possibly as a
  result of progesterone action.

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Gastrointestinal

• Pyrosis (heartburn) is common is caused by
  reflux of acidic secretions into lower esophagus
  decreased tone of sphincter.

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Gastrointestinal

• Intraesophageal pressure is lower intragastric
  pressure is higher in pregnant women.
• Esophageal peristalsis has lower wave speed
  lower amplitude.

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Gastrointestinal

• Gastric emptying time is unchanged during
  pregnancy,but during labor and with
  administration of analgesics prolonged that lead
  to aspiration.
• Reduced motility in small intestine lead to
  increase time of absorption.
• Reduced motility of large intestine lead to
  increase time for water absorption that
  predisposes to constipation.

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Hepatobiliary

• No increase in size of the liver of pregnant
  woman.
• There is no distinct changes in liver morphology
  as evidenced by histological evaluation of
  postmortem liver biopsies by EM.
• Despite this, there is increase in diameter of
  portal vein its blood flow.
• Liver function tests varies greatly during normal
  pregnancy.
• Serum alkaline phosphatase almost doubles (heat
  stable placental alkaline phosphatase isozymes).

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Hepatobiliary

• Serum AST,ALT, bilirubin levels are slightly
  lower than non pregnant normal values.
• Serum concentration of albumin decreases.
• Decrease in albumin to globulin ratio occurs due
  to combined reduction in albumin concentration
  slight increase in serum globulin levels.

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Gallbladder changes

• Reduced contractility of the gallbladder.
• Progesterone impairs gallbladder contraction by
  inhibiting cholecystokinin-mediated smooth muscle
  stimulation,primary regulator of gallbladder
  contraction.
• Impaired motility leads to stasis, and this
  associated with increase cholesterol saturation
  of pregnancy leads to cholesterol stone in
  multiparous.
• Pregnancy causes intrahepatic cholestasis
  pruritus gravidarum from retained bile salts.
• Cholestasis of pregnancy is linked to high levels
  of estrogen which inhibit transductal transport
  of bile acids,also increased progesterone
  genetic factors has been implicated in
  pathogenesis.

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Urinary system

• Striking anatomical changes are seen in the
  kidneys and ureters.
• This is due to changes in pelvic anatomy and is
  a feature of 'normal' pregnancy.
• Frequency of micturition is a common symptom of
  early pregnancy and again at term.

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Urinary System

• A degree of hydronephrosis and hydroureter
  exists.
• loss of smooth muscle tone due to progesterone,
  aggravated by mechanical pressure from the uterus
  at the pelvic brim.
• VUR is also increased.
• These changes predispose to UTI.

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Urinary system
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Neurological

• Women often report problems with attention,
  concentration, memory throughout pregnancy
  early postpartum period.

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Neurological

• In a longtudinal study done by keenan colleagues
  (1998) investigating memory in pregnant women by
  a matched control group, they found (pregnancy
  related decline in memory limited to 3rd
  trimester un attributable to depression ,anxiety
  ,sleep deprivation or any other physical changes
  associated with pregnancy.

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Neurological

• Zeeman and co-workers (2003) used MRI to measure
  cerebral blood flow across pregnancy in 10
  healthy women.
• They found that mean blood flow bilaterally in
  the middle and posterior cerebral arteries
  decreased progressively from 147 and 56 ml/min
  when non pregnant to 118 and 44 ml/min late in
  the third trimester, respectively.
• The mechanism and clinical significance of this
  decrease, and whether it relates to the
  diminished memory observed during pregnancy is
  unknown.

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Musculoskeletal

• Progressive lordosis compensates for the anterior
  position of the enlarging uterus.
• Increased mobility of sacroiliac, sacrococcygeal
  pubic joints(not correlated to increased levels
  of maternal estrogen, progesterone relaxin
  levels.
• Joint mobility causes low back pain which is
  bothersome late in pregnancy.

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Musculoskeletal

• Bones ligaments of pelvis undergo remarkable
  adaptation
• Relaxation of the pelvic joints, particularly
  symphysis pubis
• Symphyseal diastasis

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Dermatological

• Reddish, slightly depressed streaks commonly
  develop in the skin of the abdomen and sometimes
  in the skin over the breasts and thighs.

Striae gravidarum
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Dermatological

• The midline of the abdominal skin linea alba
  becomes markedly pigmented, assuming a
  brownish-black color to form the linea nigra.

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Dermatological
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Weight Changes

• Metabolic changes, accompanied by fetal growth,
  result in an increase in weight of around 25 of
  the non-pregnant weight.
• Approximately 12.5 kg in the average woman.

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Weight Changes

• There is marked variation in normal women but the
  main increase occurs in the second half of
  pregnancy and is usually around 0.5 kg per week.
• Towards term the rate of gain diminishes and
  weight may fall after 40 weeks.
• The increase is due to the growth of the uterus
• and its contents, breasts and increase in
  maternal blood volume and interstitial fluid.

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Ophthalmic

• Decrease in intraocular pressure due to increased
  vitreous outflow.
• Decreased corneal sensitivity especially, late in
  gestation.
• Slight increase in corneal thickness thought to
  be due to edema.

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Ophthalmic

• Thats why pregnant women may have discomfort
  with previously comfortable contact lenses.
• Increase frequency of Krukenberg spindles
  (hormonal).
• Visual function remains unaffected except for
  transient loss of accomodation.

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Dental

• Gums may become hyperemic soft during pregnancy
  and may bleed if mildly traumatized as with a
  toothbrush.

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Dental

• Epulis of pregnancy (a focal highly vascular
  swelling of the gum develops occasionally
  regresses spontaneously after delivery.
• Most evidence indicates that pregnancy doesn't
  incite tooth decay.

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