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Maternal Physiology: Dr. Austria
UTERUS
Change in size, weight, and capacity
Transformed into a muscular sac
Total volume: ave. !iters
"terine weight may reach appro#. $$%%g
"terine enlargement involves stretching and
mar&ed hypertrophy of muscles
"terine hypertrophy is pro'a'ly stimulated 'yestrogen and progesterone after $(w&s
increase in size is related predominantly to
pressure e#erted 'y the e#panding products
of conception
"terine musculature in pregnancy is arranged
as:$. )uter hoodli&e layer arching over the
fundus and e#tending into the various
ligaments(. Middle layer composed of dense networ&
of muscle *'er perforated in all directions.
+. nternal layer with sphincter-li&e *'ersaround the fallopian tu'e ori*ces and
internal os of the cervi#
Braxton-Hicks contraction noted during
early pregnancy 'ecoming more fre/uent with
pregnancy approaches termo "npredicta'le, sporadic and non rhythmic
contractions with pressure varying from -
(mm0g
Uteroplacental Blood Flow
o Placental perfusion is dependent upon
total uterine 1ow
o "teroplacental 'lood 1ow increasesprogressively ranging from 2%-3%ml4min
near termo "terine contractions decreases uterine5s
'lood 1ow in proportion to the intensity of
the contraction
UTERUS
6egulation of "teroplacental 7lood 8low
Progressive increase in uteroplacental 'lood
1ow occurs principally 'y means of
vasodilation:o 8etal placental 'lood 1ow in increase 'y
continuing growth of placental vessels.o 9asodilation is at least in part the
conse/uence of estrogen stimulation and
in part due to progesteroneo igni*cant decrease in uterine 'lood 1ow
and placental perfusion have 'een show
following nicotine and catecholamine
infusion.
o ;ormal pregnancy is characterized 'y
vascular refractoriness to the pressure
e? musculature undergoes little hypertrophyduring pregnancy
9A=;A A;D P>6;>"M? Chadwic& sign- due to increased vascularity andhypermedia of the vagina? vaginal wall changes include:
? increased thic&ness of mucosa? loosening of connective tissue
? hypertrophy of smooth muscle cells? hypertrophy of papillae of vaginal
mucosa
B;? increased cutaneous 'lood 1ow serves todissipate e#cess heat due to increasedmeta'olismA'dominal wall
? striae gravidarum or stretch mar&s? diastasis recti
Pigmentation
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? !inea ;egra - mar&ed pigmentation ofthe midline of the a'dominal s&in
? chloasma or melasma gravidarum -mas& of pregnancy
? due to elevation of melanocytestimulating hormones9ascular changes
? angiomas or vascular spiders? palmar erythema
76>AT? early wee&s of pregnancy - 'reast tendernessand tingling? increase in size and appearance of delicateveins 'eneath the s&in gigantomastia- needssurgery? larger, deeply pigmented and more erectilenipples? colostrum - thic& yellowish 1uid may 'ee#pressed from the nipples
M>TA7)!C C0A;=>
Eeight gain? attri'uta'le to the uterus and its contents,'reasts, increase in 'lood volume and e#travascular >C8? increase on cellular water and deposition ofnew fat and protein? averages a'out $(. &h or (@. l's? ( l's for o'ese? + l's for underweight
Eater meta'olism? increased water retention occurs normally- duein part to fall in plasma osmolality induced 'yresetting of osmotic threshold for thirst andvasopressin secretion? minimum amount of e#tra water duringpregnancy is a'out 3.!
? +. ! - fetus, placenta, amniotic 1uid? + ! - maternal 'lood volume, size of
uterus, 'reast? edema of an&les and legs - due to increasedvenous pressure? maternal 'ody water rather than fat contri'utesto infant 'irthweight
protein meta'olism? a'out half of the total pregnancy increase isdue to protein rather than fat and car'ohydrate? nitrogen 'alance progressive increases withgestation
Car'ohydrate meta'olism? normal pregnancy is characterized 'y:
? mild fasting hypogly? postprandial hyperglycemia? hyperinsulinemia
? pregnancy induced state of peripheralresistance to insulin, the purpose is to ensure
sustained supply of glucose to the fetus - 2 to@%F lower sensitivity? possi'le mechanisms of insulin resistance:
$. Progesterone and estrogen maymediate resistance
(. ncreased concentration of circulating88A may aid tissue resistance to insulin? the pregnant woman changes rapidly from apostprandial state characterized 'y elevated and
sustained glucose levels to a fasting statecharacterized 'y decreased plasma glucose andamino acids - switch in fuel from glucose to lipids- referred as ACC>!>6AT>D TA69AT);? central fat
8at meta'olism? lipids, lipoproteins and apoliproteins in plasmaincreases apprecia'ly during pregnancy? fat storage and deposition occurs mostlycentrally? fat can 'e energy source protecting mother
fetus during prolonged starvation and hardphysical e#ertion? maternal hyperlipidemia occurs during latepregnancy
>lectrolyte and mineral meta'olism? nearly $%%% m>/ of sodium and +%% m>/ ofpotassium is retained during normal pregnancy? total serum calcium and magnesium declineduring pregnancy? serum phosphate is within nonpregnant range? considera'le increase in iron re/uirement
0g' (nd trimester must 'e G$%. mg4d!+rd trimester must 'e G$$ mg4d!
7lood volume? maternal 'lood volume increases 2%-2F a'ovethe nonpregnant level at or very near term? functions of pregnancy induced hypervolemia:
? meet the demands of enlarged uteruswith its greatly hypertrophied vascular system
? protect mother and features from thedeleterious e
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? iron re/uirement during (nd half of pregnancyis 3-@ mg4d!
mmunological4 leu&ocyte functions? suprresssion of a variety of humoral and cellmediated immunological functions in order toaccommodate the fetus? pea& levels of gA and = are higher in thecervical mucus enhancing local 6T immunity
? leu&ocyte count varies considera'ly duringpregnancy
Coagulation? coagulation cascade is in an activated state? increase in all clotting factors e#cept H and H? clotting times however does not di/uili'rium
Physiologic dyspnea may 'e noted
May 'e due to increased Total 9olume thatlowers the 'lood PC)( level slightly
Progesterone and estrogen cause increasedrespiratory epulis of pregnancy focal highly vascular
swelling of gum 0emorrhoids caused 'y constipation and
elevated pressure of the veins 'elow theenlarged uterus
!iver
Diameter of portal vein and its 'lood 1ow is
increased
Alteration of la'oratory test results li&e =PT,
=)T, 'iliru'in test are decreased whileal&aline phosphatase actively dou'les
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=all7ladder
6educed contracta'ility of the gall'ladder
smooth muscle
tasis and increased choledterol saturation
may increase prevalence of cholesterol stonesamong multiparous women
Pruritus gravidadum due to retained 'ile
salts
Propensity for pregnancy to cause
intrahepatic cholestasis
>;D)C6;> JT>MPituitary =land
>nlarges a'out $+F
Maternal pituitary gland is not essential for
maintenance of pregnancy
=rowth hormone principal source is the
placenta 'y $@thwee&
Prolactin increases mar&edly during
pregnancy
Thyroid =land+ modi*cations in the regulation of Thyroid0ormone:
$. ncreased thro#ine 'inding glo'ulin due toestrogen
(. >#cess thyroidal stimulatory factors fromplacenta
+. Decreased availa'ility of iodide for maternalthyroid
"ndergoes moderate enlargement due to
glandular hyperplasia and increasedvascularity
Comple# alteration in the thyroid regulation
do not appear to alter maternal thyroid statusas measure 'y meta'olic studies
0C= has intrinsic throdotropin activity
resulting in thyroid stimulation andthyrotropin level decrease
7M6 increases to as much as (F - most of
increase in )( consumption due to fetalmeta'olic activity
Prolactin
Mar&edly increased during pregnancy $%#
greater
Plasma concentration decreses following
delivery
Principal function of prolactin is to ensure
lactation
Prolactin is present in the amniotic 1uid in
high concentration and is pro'a'ly importantto prevent fetal dehydration
Parathyroid =land
tudies have shown that all mar&ers of 'oneturnover increased during pregnancy and thatcalcium needed for fetal growth and lactationmay 'e drawn at least in part from maternals&eleton
PT0 initially decreases during $sttrimester
then progressively increases duringpregnancy 'ecause of lower calciumconcentration
Physiological hyperparathyroidism in
pregnancy ensures an ade/uate supply ofcalcium to the fetus
Calcitonin level are also increased to protect
maternal s&eleton calci*cation
Adrenal =land
"ndergoes little if any morphological change
erum concentration of serum cortisol is
increased 'ut much of it is 'ound 'ytranscortin
ncreased secretion of aldosterone was noted
in as early as $ wee&s of pregnancy reachinga'out $mg4day 'y the +rdtrimester ofpregnancy
ncreased aldosterone secretion in normal
pregnancy a!>TA! JT>M
Progressive lordosis is a characteristic feature
7ones and ligaments undergo remar&a'le
adaptation during pregnancy