Maternal anatomical, physiological and biomechanical changes during pregnancy

Physical Therapy for Women's Health - 4th Year Students - SVU

4. -Pregnancyis associated with normal
anatomical,biomechanical& physiological
changesto provide suitable environment for fetal
development, to cater to the increased metabolic
demandsand to prepare for the childbirth.
-It is important tohealthcare professionalsto
know the normal parameters of changein order
to diagnoseand managecommon medical
problemsof pregnancy, such as hypertension,
gestational diabetes, anemiaand
hyperthyroidism.

5. The Reproductive System Changes
(1) Changes in the uterus are phenomenal. By the time
the pregnancy has reached term, the uteruswill have
increased about five timesits normal size:
(a) In lengthfrom 8to 35cm.
(b) In depthfrom 2.5to 20cm.
(c) In widthfrom 5to 25cm.
(d) In weightfrom 50to 1000grams.
(e) In thicknessof the walls from 1.25to 0.5cm.
A. Uterus:

6. (2) The capacityof the uterus must expand to normally
accommodate a 3.5 Kg fetus and the placenta, the
umbilical cord, the amniotic fluid, and the fetal
membranes. So, it increases from
4 ml in non-pregnant state to 4000 ml at term.
(3)During pregnancy as the uterusexpands and moves
out of the pelvis, the round ligaments and the
uterosacral ligaments can be stretchedwhich causes
discomfortin some women.
(4)Formation of lower uterine segment: After 12 weeks,
the isthmus(0.5cm) starts to expand graduallyto form the
lower uterine segment which measures 10 cm in length at
term.

7. (5) The abdominal contents are displaced to the sides as
the uterus grows, the uterus usually undergoes rotation
with tilting to the right(dextro-rotation), probably due
to presenceof the rectosigmoid colon on the left side.
-The sizeof the uterus usually reaches its peak at 38 weeks
gestation. The uterusmay drop slightly as the fetal head
settles into the pelvis, preparing for delivery. This dropping
is referred to as (lightening).
-The increaseof uterine weight is due to hypertrophy of the muscle fibers(estrogen effect),
their multiplication(progesterone effect) and the increasedmass of elastic connective tissue.
-From the first trimesteronwards, the uterus undergoes irregular contractionscalled
(Braxton Hicks Contractions), which normally are painless.

8. -Formation of the Placentathat begins after blastocyst
implantation in the uterine wall.
-The placentais the temporary organ that plays a critical role
regarding connectionbetween the fetusand the mother.
-Throughout the pregnancy, It suppliesnutrientsand oxygen
and eliminates waste products of the fetus via the umbilical
cord (through one umbilical vein whichimports oxygenated
bloodto the fetus and two umbilical arterieswhichexport
deoxygenated blood from the fetus). Also, the placenta
producesseveral hormonesthroughout pregnancy, each of
which plays an important role in supportingthe pregnancy as:
Chorionic gonadotropin hormone, estrogens, progesteroneand
human placental lactogen.

10. -The Cervixbecomes hypertrophied, softand bluishin color due
to edemaand increased vascularity.
-After conception, a thick cervical secretion result of enlarged
and activemucus glandsof the cervixobstructs the cervical canal
forming a mucous plugserves to sealthe uterus and to protect
the fetus and fetal membranes from infection. The mucus plug is
expelledat the end of the pregnancy.
B. Ovaries:
-Both ovariesare enlargeddue to increased vascularity and
edemaparticularly that containing the corpus luteum.
-Corpus luteum starts to degenerateafter the 10th week of
gestation which secretes estrogen, progesteroneand relaxin.

11. -Ovulationceasesduring pregnancydue to pituitary
inhibitionby the highlevels of estrogenand progesterone.
C. Fallopian Tubes:
-The musculaturehypertrophiesand the epitheliumbecomes
flattened.also, sometimesif fertilized oocyte grows outside
the uterus this is called an ectopic pregnancy(90%occurs
in fallopian tubes), this can rupturefallopian tubesleading to
a major internal bleeding. It is a life-threatening emergency.
D. Vagina:
-Increased circulation to the vaginaearly in pregnancy changes as the vaginal walls become
more hypertrophied and more vascular.
-During pregnancy, pHof the vaginabecomes more acidicand may develop varicose veins.

12. -Pregnancy hormones cause normal breast
tissue to change into milk-producing tissue.
This change occursas earlyas the first trimester.
-As pregnancy progresses, the nipplesand the
areolamay darkenin color also, beginning in
production of colostrumduring the first few
weeks of the second trimester.
-Estrogenencourage growthand branchingof
thelactiferous ductsduring pregnancy,
Progesteronecauses enlargementof lobules,
Prolactinprepares for milk production and
Oxytocinincreases at the onset of labor and
during labor as a preparation formilk ejection.

13. The Endocrinal (Non-Reproductive)
System Changes
Pituitary hormones
-FSH/LH fallto extremely low levels due to the high
levels of estrogen and progesterone.
-ACTHlevels increase.
-Melanocyte-stimulating hormone levelsincrease.
-TSHlevels may increase.
-Prolactinlevels increase.
-Pituitary growth hormone (GH) levels fallbut overall
serum levels increasedue to placental production.
-Oxytocinlevels increaseto a peak at term.
-ADHlevels are unchanged.

14. Thyroid hormones
-Thyroxine-binding globulin (TBG) concentrations
risedue to increased estrogen levels.
-T4and T3increaseover the first half of pregnancy
but there is a normal to slightly decreased amount of
free hormonein the secondand third trimester due to
increased TBG-binding.
-TSHproduction is stimulated after the first trimester, a large rise in TSH is likely to indicate
iodine deficiency or subclinical hypothyroidism.
-Untreated maternal hypothyroidism can lead to increased risk of miscarriage, gestational
hypertension, preterm birth, low birth weight, and respiratory distress in the neonate.

15. Adrenal gland and Pancreatic hormones
-Cortisollevels increasein pregnancy, which favors
lipogenesisand fat storage.
-Insulinresponse also increasesso blood sugar should remain
normal or low due to insulin resistance.
Peripheral insulin resistance increases after early stagesof
pregnancydue to increased production of hormones such as
cortisol, prolactin, progesteroneand human placental lactogen.
-Gestational diabetes is thought to reflecta pronounced insulin
resistanceof this sort.
-HbA1cis not considered suitable for use in pregnancy.

16. The Cardiovascular System Changes
-As the diaphragmis elevated progressively during pregnancy
the apex is displaced upwards and to the leftso that it lies in
the 4th intercostal space outside the midclavicular line.
-Cardiac outputincreasesby20%byweek 8, and then
further up to 40% increase, maximal at week 20-28.
-In labor(Particularly during the 2
nd
stage) there is further
increasein cardiac output due to pain,uterine contractions
andbearing down. then a huge increase immediately after delivery.
-Contributing to the increased cardiac output are increased stroke volume and an
increasein restingheart rate of 10-15beats per minute.

17. -There is a peripheral vasodilationdue to estrogenand
progesteroneeffect so,Blood pressure is lowerthan normal in
the first two trimesters butreturns to normalin the third trimester.
-The postureof the pregnant woman affects arterial blood
pressure. Typically, it is highestwhen she is sitting, lowest
when lying in the right lateral recumbent positionand intermediatewhen supine.
-Supine hypotensive syndrome may develop in some women
latein pregnancyin supine position. This is due to compression
of the inferior vena cava by the large pregnant uterusresulting in
decrease venous return, decrease cardiac outputand low blood
pressurethat faintingmay occur so, left side lying position is the best during these months.
-Changes on examinationand ECGare caused by these physiological changes.

18. The Respiratory System Changes
-Tidal volume increasestoprovide more oxygenation (Oxygen consumption
is increased 20%) and respiratory rate does not alter significantly.
-The chest vertical diameter is decreaseddue to enlarged uterus
that compressthe diaphragm superiorly, butthe anteroposterior
and transverse chest diametersare increased.
-The average subcostal angleof the ribs at the xiphoidal level
increasesfrom 68.5°at beginning of pregnancy to 103.5°at term.
-Hyperventilationwith a state of compensated respiratory
alkalosis -arterial pCO2drops, arterial pO2rises. Lower maternal
pCO2facilitates oxygen/carbon dioxide transferto/from the fetus.

19. Non-Pregnant and Pregnant Lung Volumes

20. The Gastrointestinal System Changes
-Nauseaand vomitingare commonin early pregnancy
(Hyperemesis Gravidarum).
-The pregnant woman dislikes some foodsand odorswhile
desires others (Longingor Craving). Reduced sensitivity of
the taste buds during pregnancy creates desire for markedly sweet or salt foods.
-Progesteronecauses relaxationof the lower esophageal sphincter
and increased liability to heartburn. Pressure on the stomachfrom
the enlarging uterus further contributes to this in later pregnancy.
-Gastrointestinal motilityis reduced, and This allows increased nutrient
absorption. Constipationand piles(due to pressure on pelvic veins) are common.

21. -Also, Constipationmay be due to sedentary life duringpregnancy
andincreased water reabsorption from large intestine (aldosterone effect).
-The Gallbladdermay dilate and empty less completely.
Pregnancy also predisposes to the precipitation of cholesterol gallstones.
-Gingivitis, Gumsbecome spongy, friable,highly vascularand prone to
bleeding in about 50% of pregnant women due to hormonal changes give
rise to inflammation in the gums where the gums are more sensitive to
the bacteria.
-Excessive Salivation is more commonand Indigestionis pronounced
due to decreased gastric acidity caused by regurgitationof alkaline
secretion from the intestineto the stomachand decreased gastric
motility(Progesterone effect).

22. The Urinary System Changes
-The increased blood volume and cardiac output during pregnancy
cause a 50-60% increase in renal blood flow and glomerular
filtration rate (GFR). This causes an increased excretion and
reduced blood levels of urea, creatinine and bicarbonate.
-Mildglycosuriaand/or proteinuriamay occur because the
increase in GFR may exceedthe ability of the renal tubules to
reabsorbglucose and protein.
-Under Progesterone effect,the smooth muscle of the renal pelvis
and ureterbecome relaxedand dilated (especially the right side due
to dextrorotation), kidneysincreasein length and uretersbecome
longer, more curved and with an increasein residual urine volume.

23. -Urinary stress incontinence may develop for the
first-time duringpregnancy.
-Bladder smooth muscle also relaxes, increasing
capacityand riskof urinary tract infection.
-Frequentmicturitionis commonin the firsttrimester
(due to congestionand pressureof the bladderby
theenlarged uterus) and third trimester ( due to pressure
by the presenting partafter engagement).
-During pregnancy, mildhydronephrosisespecially on
the right side due to uterine dextrorotation is considered
a normal phenomenon and may be present in up to 90%
of pregnancies.

24. The Hematological Changes
-Plasma volume increasesover the course of pregnancy by about 50%
and there is a 20% increase in the total number of red blood cells (RBCs).
-Physiologicalor dilutional anemia in pregnancyaccounts for increased
plasma volume more thanincreased red blood cellscauses hemodilution,
which is greatestduring the second trimester.
-Hemoglobinlevels are decreased, the reason that fetal growth and developmentwere
higherin the secondand third trimesters which consumes a lot of nutrients from the mother.
-Iron deficiency is the most common nutritional deficiency in the world,
If developed during pregnancy, it significantly alters pregnancy outcomes as: low birth
weight, premature delivery and poor milk production.

25. -Hemoglobin concentration:lowerthan
11.6 g/dlin the first trimester,
9.7 g/dl in the second trimester,
and 9.5 g/dlin the third trimester
labeled as anemiafor pregnantwomen.
-Anemiais the majorcontributory or sole cause in
20–40%of maternal deaths.
-Levels of some clotting factors (VII, VIII, IXand X), plateletsand
fibrinogenincreasewhilst fibrinolyticactivity decreases. These
changes protectfrom hemorrhageat delivery butalso make pregnancy a
hypercoagulable state with increasedliability of development of DVT.
-There is an increaseleucocytes.

26. The Metabolic Changes
-The basal metabolic rate increases slowly over the course of pregnancy, by 15-20%.
-Active energy expenditure tends to fallover pregnancy.
-It is thought that energy requirement does notincrease
significantlyduring the firstor secondtrimesters.
-During the 1st trimester, the increasein weightis about
(1.6Kg), during the 2nd trimester(5.5-6.4Kg) and in the 3rd trimester only around 5 kg.
-There is tendencyto water retention secondary to sodium retention.
-There is increased demandfor iron, calcium, phosphateand magnesium.

27. The Integumentary System Changes
-Hyperpigmentationof the umbilicus, abdominal midline
(linea nigra) and face (chloasma gravidarum)) are common
due to pregnant hormonalchanges especially highMSH.
-Hyperdynamic circulation and highlevels of estrogen
may cause spider angioma and palmar erythema.
-Increased sweatand sebaceous glands activity, hair loss
and brittlenessof nailsare also commonin pregnancy.
-Striae gravidarum (stretch marks) are common it begins
as (striae rubre) red colorthen it becomes
(striae albicantes) white colordue to fibrosis.

28. The Musculoskeletal System Changes
-Increasedligament laxity is a physiologicalprocess caused by
increasedlevels of Relaxin,estrogensand Progesteronehormones
contribute to back pain, sacroiliacand pubic symphysis dysfunctions.
-Relaxin isa hormone secreted by the corpus luteum and the placenta
duringpregnancy.
-Relaxinwas shown to directlyinhibit fibroblast differentiation into
myofibroblastexpression, activatethe collagenase enzyme which inhibit
collagen synthesis,decrease itstensile strength and deposition.
-Pregnant Joint pain (low back and hips) may be related to mechanical
changes and decreased ambulationrather than increasing laxity.

29. -Unlikeboneand musclewhere estrogenimprovestheir
function, in tendonsand ligamentsestrogendecreases
their stiffness, and directlyaffects performance and injury rates.
-Highestrogenlevels can decrease power and performance
and make womenmore prone for catastrophic ligamentinjury.
-Diastasis recti is the partialor completeseparationof the
rectus abdominis. it is very common duringand following
pregnancy. This is because the uterusstretches the muscles
in the abdomen to accommodatethe growing baby.
-For many women, pregnancy, as well as parturition,
represent the key physiological events predisposing to
pelvic floor dysfunction and incontinence.

30. The Postural Changes
-With weight gain, increased blood volume and ventral growth of the
fetus, the center of gravity no longer falls over the feet and women
may need to lean backwards to gain equilibriumresulting in
disorganization ofspinal curves.
-Reported posturesinclude an increasein bothlumbar lordosis and
thoracic kyphosis or a flattening of the thoracolumbar spinal curve.
-There will be compensatory changes to posturein the thoracicand
cervicalspines, and this combined with the extra weight of the
breastsmay result in posterior displacement of the shouldersand
thoracic spine and increaseof the cervical lordosis.

31. -COGshifts upwardand forward
because of the enlargementof the uterus
and breast tissue.
-The lumbarand cervical lordosis
increasewhile knees are hyperextended.
-The shoulder girdle and upper back
become roundedwith scapular
protractionand upper extremity internal
rotation.
-Weightshifts toward the heelsto bring
COGto a more posterior position, so
planter fasciitis is commonin pregnancy.

33. -Not only the torquesof bilateral hip extension of pregnant females during the secondand
third trimesters were smaller thanthe non-pregnant females but also, the bilateral planter
flexion torquesin pregnant females were largerduring the third trimester than the non-
pregnant females.
-The biomechanical alterationsin step width and lengthwhich are consequences of
anterior tilting of the pelvisand wide pregnant pelvis.
-The gaitof the pregnant women changed, reductionof
gait velocity, swing phase and increasedhip internal rotation.
-Shift in posturewith exaggeratedlumbar lordosis, weakhip
abductors leading to the typical gait of late pregnancy.
-Pronatedfeet, kneesout, backarched. it’s the pregnant-woman penguin waddle.

34. -Almost a quarterof the pregnant women experience
fallingat least once and the risk of falling during
pregnancy is the highestduring the 3
rd
trimester
especiallyduring the seventh month of gestation.
-The falling rate during pregnancyis very closeto that in
elderlywomen (26.8%and 29%respectively).
-Unfortunately, fallsare the major cause for admission to
emergency department in pregnancy that can be attributed
to that Pregnant women face many anatomical,
physiological, and mechanicalchanges which may be
behind the increasedrisk of fall.
Risk of falling during pregnancy

35. -The center of gravity is shifted superiorlyand anteriorlyand the dynamic
postural controlthat is declined to its lowestlevels during this 3rd trimester.
-When maintaining a standing posture, the ankle joint strategy, hip joint
strategyand step strategy are the three movement strategies used to counter
anterior-posterior translational motion.
-Postural swayof anterior-posterior movements
increasedand the ankle joint strategytakes seniority
over the hip joint strategy in maintaining balance
during pregnancycompared to non-pregnancy as they
use their hip joint extensors lessand their ankle plantar flexors more.
-Relianceon the ankle joint strategy indicates that they would have difficulty
controlling movement as the base of support shifts from the center outwards.

36. -Fallingduring pregnancymay cause serious complications to
pregnant woman and fetus.
-These fallingcomplicationsmay include the following: traumatic
head injuries, maternal fractures, placental abruption, uterine rupture,
premature rupture ofmembranes, internal bleeding and sometimes
maternal death or stillbirth.
-Fracture neck of femur may be a complicationof fallduring
pregnancy (due to trauma, transient osteoporosisduring pregnancy
and weak hip abductors as when they contractthere is a decreasein
the bending forces on the neckof femur).
-Pelvic fractures as pubicor acetabularfractures in pregnant
womenare associated with riskof mortalityto both mother& fetus.

37. Neuromuscular System Changes
-Passive joint instability (as seen in pregnancy) altersafferent
inputfrom joint mechanoreceptors and probably affects motor
neuron recruitment.
-A decreasein muscle stiffness and thus active stability of joints
may result from alterationof muscle spindle regulation and
this is applicable particularly to musclesaround the pelvic girdle.
-These changes may lead to poor recruitment of the muscles
responsible for pelvic girdle stability (particularly gluteus
medius and maximus)and result in decreased tension of these
muscles during walking, perhaps resulting in pelvic girdle pain.

38. -Carpal tunnel syndrome (CTS) is the most common compression
neuropathyof median nerve, which can occuror aggravateduring
pregnancy, with a prevalence reported as high as 62%.
-Commonchief complaintsof CTSare numbness, tingling,
burningin median nerve region as well as the lossof grip strength.
-In pregnancy, the likely causesof CTSare hormonal changesand edema. Gestational
diabetescan also play a role due to generalized slowing of nerve conduction.
-Sciaticadue to a herniated disc during pregnancy isn’t common. But
sciatic-like symptomsare commonwith low back pain in pregnancy.
-Sciaticsymptoms can be caused by muscle tension (Tight piriformis) and unstable joints are
common causesof sciatic pain rather than enlarged uterine compression during pregnancy.

39. -Meralgia paresthetica (lateral femoral cutaneous
nerve entrapment)is a condition characterized by
tingling, numbnessand burning pain in the outer thigh.
-The causeof meralgia paresthetica is the growing
uterusand weight gain can put pressureon the groin
that lead to compressionof the nerve underthe inguinal
ligament so, the sensationto the skin of anterolateral
surface of the thighis affected.
-While it is often reported as a self resolving disorder, it can prove to be very uncomfortable
and even disablingfor patients and shown to last for a duration of up to 16 months.
-Pudendal nerve terminal motor latency did notincrease significantly during pregnancybut
increased significantly after delivery.

40. Prophet Muhammad (PBUH) said
“Treat women kindly”