Obs.& Gyn.
2nd lecture
PH.TH. 403
Anatomical and physiological changes during
pregnancy of different body systems.
 In all mammalian species, there are extensive biochemical,
physiological and structural changes during pregnancy and the
puerperium:
 The causes of these changes are:
1. To provide a suitable environment for nutrition, growth
and development.
2. To prepare the mother for the process of parturition and
subsequent support of the new born baby.
All changes that occur in pregnancy to achieve these objectives are
both visible and suitable.
The Cervix:
 Physiological and anatomical changes::
During pregnancy,: The cervix is closed by a mucus plug providing
a protective barrier between the vagina and the uterine contents.
During labor and delivery: The cervix shorten and widen (dilates),
A 10 cm opening is left between the uterus and vagina to allow passage
of the fetus into the birth canal.
Cerclage: is a dilatation of the cervix prematurely.
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Obs.& Gyn.
2nd lecture
PH.TH. 403
The Uterus:
The uterus will:
1)
↑ weight from 60 to 1000g
2)
↑ size from 6.5 to 32 cm
3)
Expands into the abdominal cavity due to:
The growth of the fetus
↑ in connective tissue
↑ the size and number of blood vessels supplying the uterus
Cardiovscular changes
Itravascular volume changes:
During pregnancy:
 ↑ Heart rate, reaching a peak of 10 to 15 beats/min over non
pregnant values.
 ↑ Blood volume 40% above non pregnant values.
 ↑ Cardiac out put up to 30% to 50% at 28 to 32 weeks of pregnancy.
 ↓ Arterial blood pressure due to :
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Obs.& Gyn.
2nd lecture
PH.TH. 403
Reduction in systemic vascular resistance.
Reduction of peripheral vascular tone. (release of relaxin hormone.
 Maternal position has an effect on blood pressure particularly if the
uterus compresses the inferior vena cava. This occurs in lying
position and disappears in the left sidling position, (supine
hypotension or Vena cava syndrome) affects 3% to 11% of pregnant
women.
 Occlusion of inferior vena cava leads to:
↓ Venous return.
↓ Central venous pressure.
↓ Left ventricular output.
↓ Cardiac output by 25%
No change in pulse or blood pressure due compensatory
vasoconstriction.
 Mitral valve prolapsed is the most common problem of
pregnant women.
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Obs.& Gyn.
2nd lecture
PH.TH. 403
Respiratory system:
During pregnancy:
1) Breathing becomes more costal than abdominal or diaphragmatic.
Additionally most women are mouth breathers during pregnancy.
2) The diaphragem is elevated due expansion of the uterus.
3) No change of respiratory rate, ↑ oxygen consumption.
4) ↑ Respiratory tidal volume by 200ml resulting in deeper breathing.
5) ↑ Respiratory minute by 29% due to ↑ in progesterone hormone level
Breast Changes:
 Increased blood flow to breasts
 Increased size of breasts
 Increased ductal growth, alveolar enlargement.
 Lactation dependent on the release of the following hormones:
Estrogen, Prolactin, Progesterone, Cortisol, Insulin.
Skin Changes:
 Increased estrogen levels may cause:hyper pigmentation between
the umbilicus and symphysis pubis , nipples(1st and2nd areola,
abdominal midline (linea Ingra) and mask face, which is butterfly
pigmentation of the forehead, nose, upper lip and checks (chloasma
gravid arum).
 Hyper dynamic circulation and high levels of estrogen may cause:
spider naevi and palmer erythema.
 Stria gravid arum ("stretch marks") due to: over stretching of the
skin, the elastic fibers may rupture together with small blood vessels,
more marked below the umbilicus, on the breast, the buttocks and
thighs (appear in some women).

Falling of hairs and brittleness of nails may occur during
pregnancy.
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Obs.& Gyn.
2nd lecture
PH.TH. 403
Weight Gain in Pregnancy:
Normal weight gain is approximately 12.5kg (usually at a rate of
0.5kg per week for the last 20 weeks). 5kg is the fetus, placenta,
membranes and amniotic fluid and the rest maternal stores of fat
and protein and increased intra and extra-vascular volume.
Daily energy requirements in pregnancy are increased to about
2000-2500calories per day.
Associated with good outcome, i.e. delivery of normal sized baby
Total pregnancy expenditure is 75,000kcalories.
The basal metabolic rate increases by 15-20%.
Musculoskeletal Changes
During Pregnancy
 ↑ levels of relaxin may cause:
↑ ligamental laxity (↓ligamentous tensile strength, ↑mobility of
structures supported by ligaments will contribute to:
back pain and pubic symphysis dysfunction, joint injury
specially weight bearing joints of the back, pelvis, and lower
extremities.
 Shift in posture with forward head, round shoulders, exaggerated
lumbar lordosis, hyper-extended knees, and pronated feet.
 Change of the center of gravity, resulting in changes in balance.
 Change of the length of muscles.
 Total calcium levels decreased but ionized calcium levels normal
 No loss of bone density during pregnancy.
 In some pregnant women there is a tendency of decalcification of
bones and sublaxation of joints specially sacroiliac joint and
symphysis pubis, leading wadlling gait.
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Obs.& Gyn.
2nd lecture
PH.TH. 403
Urinary tract
 The smooth muscle of the renal pelvis and ureters become relaxed
and dilated

kidneys increase in length by 1cm
Ureters become longer, more curved
↑ residual urine volume.

Bladder smooth muscle also relaxes.
Gastro-Intestinal tract
• Morning sickness and vomiting in early months.
• Heart burn and indigestion.
• Constipation due pressure on the intestines by enlarged uterus,
relaxation of the smooth muscle fibers by relaxin hormone and
sedentary habits during pregnancy.
• Piles.
Metabolic and endocrine changes
 ↑relaxin hormone by corpus luteum during pregnancy and menstrual
period.
 ↑other hormones secreted by placenta, ovaries and adrenal cortex
such as: estrogen, progesterone, human placental lactogen.
 Edema in the hands, feet, face and eyelids due to water retention
and circulating hormones causing ↑ Capillary permeability
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