During pregnancy various anatomical and physiological changes occur in different systems of pregnant women.
Anatomical changes:
During pregnancy anatomical changes occurs not only in the reproductive organs but also other organs in the body.
Changes in reproductive organs:
Uterus:
Size of the uterus:
In non-pregnant, uterus is a solid structure with measurements of 9 / 6.5/3.5 cm, weight of 70 gm and volume of 10 ml.
In pregnant (at term), uterus becomes a thin walled muscular organ with measurements of 32 / 24/ 22 cm, with weight of 1100 gm and volume of 5 liters.
Uterine enlargement involves stretching & marked hypertrophy of muscle cells and limited hyperplasia.
Early in gestation this enlargement is stimulated by estrogen and progesterone.
After 12 wks, the stretching is related to the pressure exerted by the products of conception.
Enlargement is mostly marked in the fundus of the uterus.
Arrangement of muscle fibers:
The muscle fibers of the uterus are arranged in 3 strata.
An outer hood like layer arches over the fundus and extends into various ligaments.
Middle layer composed of dense network of muscle fibers perforated in all directions by blood vessels, these two layers form the main portion of uterine wall.
In these layers each cell has a double curve so that interlacing of any two gives the shape of '8'.
So, when cells contract after delivery, they constrict the penetrating blood vessels and act as ligatures.
Internal layer, consisting of sphincter like fibers around the orifices of fallopian tube and internal os .
Shape of the uterus:
In the first few weeks of the pregnancy the uterus will be in pear shape.
By 12 wks, it becomes spherical in shape.
Later, it will attain the shape of ovoid.
Position of the uterus:
Initially in pregnancy the anteversion is maintained.
As it becomes abdominal after 12 weeks, longitudinal axis corresponds to the axis of pelvic inlet unless abdominal wall is quite lax.
As it ascends, undergoes dextrorotation likely caused by rectosigmoid on the left side of pelvis.
Contractility of the uterus: Normally from first trimester onwards uterus undergoes irregular contractions.
In the second trimester, they may be detected as sporadic, unpredictable, non-rhythmic, painless contractions called Braxton Hicks contractions.
At term they become regular & cause discomfort called false labour pains.
Blood flow to the uterus:
In non-pregnant state, blood supply of the uterus is mainly through the uterine and least through ovarian arteries.
In pregnancy, the ovarian artery carries as much blood as the uterine artery.
Blood flow increases to 450 – 650 ml/min near term.
Increase is principally due to vasodilatation and fall in vascular resistance.
Remodeling of uterine veins occurs by decrease in elastin content & adrenergic nerve density resulting in increased caliber and distensibility.
As pelvic veins donot possess surrounding supporting sheath they dilate enormously during pregnancy and act as reservoir when blood is pumped out of placenta during contraction.
And also numerous lymphatic channels open up during pregnancy.
Isthmus:
It is the portion between anatomical and histological internal os.
The circularly arranged muscle fibers of this region act as sphincter and help to retain the fetus.
It progressively unfolds from above downwards beyond 12 wks until incorporated in the uterine cavity, forming lower uterine segment.
It undergoes softening earlier than fundus which is called hegar's sign.
Cervix:
As early as in the first month after conception cervix begins to undergo profound softening & cyanosis, resulting from increased vascularity & edema together with hypertrophy and hyperplasia of cervical glands.
Rearrangement of collagen necessary for the diverse functions of the cervix.
Towards term there will be inflammatory cell infiltration, breakdown and rearrangement of collagen fibers, increased hyaluronic acid , decreased dermatan sulphate, increased water content leading to thinning, softening and relaxation.
Cervical glands undergo marked proliferation and produce copious tenacious mucus.
An erosion can be seen at the cervix which is called papillary or hormonal or pregnancy erosion.
Ovary:
In ovaries ovulation ceases & maturation of new follicles is suspended.
Single corpus luteum will be there functioning maximally during the first 6 -7 wks.
Decidual reaction may be seen in the ovary.
Diameter of ovarian vascular pedicle increases from 0.9 to 2.6 cm.
Fallopian tubes:
Flattening of the epithelium of the tubal mucosa occurs.
There will be little hypertrophy of the musculature of fallopian tube. Decidual cells may develop in the stroma of fallopian tube.
Vagina & perineum:
Increased vascularity and hyperemia of skin and muscles of perineum & vulva occurs with softening of underlying connective tissue.
Increased vascularity results in violet colour of vagina which is called chadwick's sign.
Increase in the thickness of the mucosa, hypertrophy of smooth muscle cells and hypertrophy of papillae of vaginal mucosa leads to fine hobnailed appearance.
The secretions increases.
The pH becomes more acidic (3.5-6) due to lactobacillus acidophillus bacilli.
Skin:
On the abdominal wall:
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Due to rupture of subcuticular elastic fibers striae gravidarum or striae distensae or stretch marks develop.
Pigmentation:
.jpg)
Hyper pigmentation occurs forming linea nigra on the abdominal wall from umbilicus to symphysis pubis.
Pigmentation of new scars develops.
Melasma or chloasma or mask of pregnancy develops in some people.
This is due to increased estrogen, progesterone, ACTH(adrenal corticotropic hormone), MSH(melanocyte stimulating hormone) and beta endorphins.
All these will disappear or regress after delivery.
Hair:
Prolonged anagen or growing phase will be there during pregnancy due to hormonal influence.
Telogen effluvium occurs which may lead to hirsutism.
Vascular changes:
.jpg)
Augmented cutaneous blood flow occurs leading to formation of spider angioma or vascular spiders
and palmar erythema.
Breast:
The changes are more obvious in primigravidae.
Hypertrophy & proliferation of ducts and alveoli, hypertrophy of connective tissues & increased vascularity occurs.
Nipples become more erectile and areola becomes deeply pigmented. Montegmery tubercles and secondary areola forms.
After first few months, thick yellowish fluid can be expressed from nipples.
-Physiological adaptations in pregnancy - anatomical changes
-Physiological adaptations in pregnancy - weight gain, protein and fat metabolism
-Physiological adaptations in pregnancy - electrolyte and mineral metabolism
-Physiological adaptations in pregnancy - respiratory and cardiovascular systems
-Physiological adaptations in pregnancy - GIT, CNS, urinary and endocrine systems
Anatomical changes:
During pregnancy anatomical changes occurs not only in the reproductive organs but also other organs in the body.
Changes in reproductive organs:
Uterus:
Size of the uterus:
In non-pregnant, uterus is a solid structure with measurements of 9 / 6.5/3.5 cm, weight of 70 gm and volume of 10 ml.
In pregnant (at term), uterus becomes a thin walled muscular organ with measurements of 32 / 24/ 22 cm, with weight of 1100 gm and volume of 5 liters.
Uterine enlargement involves stretching & marked hypertrophy of muscle cells and limited hyperplasia.
Early in gestation this enlargement is stimulated by estrogen and progesterone.
After 12 wks, the stretching is related to the pressure exerted by the products of conception.
Enlargement is mostly marked in the fundus of the uterus.
Arrangement of muscle fibers:
The muscle fibers of the uterus are arranged in 3 strata.
An outer hood like layer arches over the fundus and extends into various ligaments.
Middle layer composed of dense network of muscle fibers perforated in all directions by blood vessels, these two layers form the main portion of uterine wall.
In these layers each cell has a double curve so that interlacing of any two gives the shape of '8'.
So, when cells contract after delivery, they constrict the penetrating blood vessels and act as ligatures.
Internal layer, consisting of sphincter like fibers around the orifices of fallopian tube and internal os .
Shape of the uterus:
In the first few weeks of the pregnancy the uterus will be in pear shape.
By 12 wks, it becomes spherical in shape.
Later, it will attain the shape of ovoid.
Position of the uterus:
Initially in pregnancy the anteversion is maintained.
As it becomes abdominal after 12 weeks, longitudinal axis corresponds to the axis of pelvic inlet unless abdominal wall is quite lax.
As it ascends, undergoes dextrorotation likely caused by rectosigmoid on the left side of pelvis.
Contractility of the uterus: Normally from first trimester onwards uterus undergoes irregular contractions.
In the second trimester, they may be detected as sporadic, unpredictable, non-rhythmic, painless contractions called Braxton Hicks contractions.
At term they become regular & cause discomfort called false labour pains.
Blood flow to the uterus:
In non-pregnant state, blood supply of the uterus is mainly through the uterine and least through ovarian arteries.
In pregnancy, the ovarian artery carries as much blood as the uterine artery.
Blood flow increases to 450 – 650 ml/min near term.
Increase is principally due to vasodilatation and fall in vascular resistance.
Remodeling of uterine veins occurs by decrease in elastin content & adrenergic nerve density resulting in increased caliber and distensibility.
As pelvic veins donot possess surrounding supporting sheath they dilate enormously during pregnancy and act as reservoir when blood is pumped out of placenta during contraction.
And also numerous lymphatic channels open up during pregnancy.
Isthmus:
It is the portion between anatomical and histological internal os.
The circularly arranged muscle fibers of this region act as sphincter and help to retain the fetus.
It progressively unfolds from above downwards beyond 12 wks until incorporated in the uterine cavity, forming lower uterine segment.
It undergoes softening earlier than fundus which is called hegar's sign.
Cervix:
As early as in the first month after conception cervix begins to undergo profound softening & cyanosis, resulting from increased vascularity & edema together with hypertrophy and hyperplasia of cervical glands.
Rearrangement of collagen necessary for the diverse functions of the cervix.
Towards term there will be inflammatory cell infiltration, breakdown and rearrangement of collagen fibers, increased hyaluronic acid , decreased dermatan sulphate, increased water content leading to thinning, softening and relaxation.
Cervical glands undergo marked proliferation and produce copious tenacious mucus.
An erosion can be seen at the cervix which is called papillary or hormonal or pregnancy erosion.
Ovary:
In ovaries ovulation ceases & maturation of new follicles is suspended.
Single corpus luteum will be there functioning maximally during the first 6 -7 wks.
Decidual reaction may be seen in the ovary.
Diameter of ovarian vascular pedicle increases from 0.9 to 2.6 cm.
Fallopian tubes:
Flattening of the epithelium of the tubal mucosa occurs.
There will be little hypertrophy of the musculature of fallopian tube. Decidual cells may develop in the stroma of fallopian tube.
Vagina & perineum:
Increased vascularity and hyperemia of skin and muscles of perineum & vulva occurs with softening of underlying connective tissue.
Increased vascularity results in violet colour of vagina which is called chadwick's sign.
Increase in the thickness of the mucosa, hypertrophy of smooth muscle cells and hypertrophy of papillae of vaginal mucosa leads to fine hobnailed appearance.
The secretions increases.
The pH becomes more acidic (3.5-6) due to lactobacillus acidophillus bacilli.
Skin:
On the abdominal wall:
.jpg)
Due to rupture of subcuticular elastic fibers striae gravidarum or striae distensae or stretch marks develop.
Pigmentation:
.jpg)
Hyper pigmentation occurs forming linea nigra on the abdominal wall from umbilicus to symphysis pubis.
Pigmentation of new scars develops.
Melasma or chloasma or mask of pregnancy develops in some people.
This is due to increased estrogen, progesterone, ACTH(adrenal corticotropic hormone), MSH(melanocyte stimulating hormone) and beta endorphins.
All these will disappear or regress after delivery.
Hair:
Prolonged anagen or growing phase will be there during pregnancy due to hormonal influence.
Telogen effluvium occurs which may lead to hirsutism.
Vascular changes:
.jpg)
Augmented cutaneous blood flow occurs leading to formation of spider angioma or vascular spiders
and palmar erythema.
Breast:
The changes are more obvious in primigravidae.
Hypertrophy & proliferation of ducts and alveoli, hypertrophy of connective tissues & increased vascularity occurs.
Nipples become more erectile and areola becomes deeply pigmented. Montegmery tubercles and secondary areola forms.
After first few months, thick yellowish fluid can be expressed from nipples.
-Physiological adaptations in pregnancy - anatomical changes
-Physiological adaptations in pregnancy - weight gain, protein and fat metabolism
-Physiological adaptations in pregnancy - electrolyte and mineral metabolism
-Physiological adaptations in pregnancy - respiratory and cardiovascular systems
-Physiological adaptations in pregnancy - GIT, CNS, urinary and endocrine systems
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