CHAPTER 7CHANGE & ADAPTATION

IN PREGNANCY

By

DR. Areefa Albahri

Assistant Prof. of MCH

Islamic University of Gaza

/ /١٤٤٤ ٠٩ ٢٩

DR. Areefa Albahri

The major maternal physiological adaptation to pregnancy

Reproductive organscardio vascular systemRespiratory changes.Changes in Central nervous systemChanges in urinary systemChanges in GI system-Blood volume homeostasisChange in metabolismChange in endocrine changes.

• The anatomical and physiological adaptations occurring throughout

pregnancy affect virtually every body system.

• The midwife's appreciation of the normal adaptations to pregnancy

and recognition of abnormal findings are fundamental in the

management of normal as well as high risk pregnancies, enabling her

to provide appropriate midwifery care to all women including those

affected by pre-existing illness.

• A common feature of these changes are influenced by physical,

mechanical, genetic and hormonal factors. Many aspects of the

physiology of pregnancy remain poorly understood and controversies

continue to be researched.

Reproductive organs

the uterus:•The uterus plays an essential role in pregnancy by expanding &

stretching to accommodate the growing fetus. it is able to contract

regularly and forcibly to expel the fetus due to its unique properties of

contractility and elasticity. The uterine wall consists of three layers: an

external serous epithelial layer or perimetrium, the middle muscle layer

or myometrium, and the internal layer of endometrium (decidua)

The perimetrium

• The perimetrium is a thin layer of peritoneum that protects the

uterus.It provides a relatively inelastic base upon which the

myometrium develops tension to increase intrauterine pressure. The

increasing tension exerted on the broad ligaments causes them to

become longer and wider, therefore it accommodate the greatly

enlarged uterine and ovarian arteries and veins.

Myometrium

• The myometrium is muscular wall of the uterus that undergoes dramatic remodeling during pregnancy and provide support to growing fetus.

• It is the layer of the uterine wall which is involved in contraction during labour.

• Its function different from upper & lower uterine segment have contractile phenotype in the upper and relax phenotype in the lower segment.

• Myometrium developed by hypertrophy and hyperplasia mechanism• By 12 week some irregular electrical cell contraction will occur known

as Braxton Hicks contractions painless some women will not feel these cont.

Endometrium (Decidua)• Decidualization prepares the uterine lining for the invading

trophoblasts .

• The decidua in the cervix and the isthmus are less well developed

than in the corpus, which prevents implantation in this region.

• This happen by rising levels of progesterone.

• The glands within the decidua may provide an important source of

nutrients, growth factors and cytokines for the fetoplacental unit

placental developed.

• The decidua also produces large amounts of prostaglandins, which

either enhances or initiates labour.

Changes in the uterine shape & size• At 5 weeks' gestation, the uterus feels like a small, unripe

pear. • By 8 weeks it feels like a large orange and by 12 weeks it

is about the size of a grapefruit.• The traditional method of assessing gestational age is to

relate the progressive increase in the height of the fundus at different gestations to abdominal landmarks throughout pregnancy.

12th week of pregnancy

• As pregnancy advances, however, the corpus and fundus assume a more globular form becoming almost spherical by 12 weeks and too large to remain totally within the pelvis.

• 16th week of pregnancy• Between 12 and 16 weeks' gestation, the fundus becomes dome-

shaped.• The uterus now increases more rapidly in length than in width. From

about 16 weeks, the internal os gradually relaxes and the lower uterine segment develops from the greatly expanded and thinned out muscular isthmus.

• 20th week of pregnancy• As the uterus rises in the abdomen, it assumes an ovoid shape, the

round ligaments appear to insert at the junction of the middle and upper thirds of the organ and the uterine tubes elongate.

30th week of pregnancy

• As the uterus continues to enlarge it contacts the anterior abdominal wall, displacing intestines laterally and superiorly and continues to rise, ultimately reaching almost to the liver.

• In the supine position the uterus falls back to rest on the vertebral column and the adjacent great vessels, in particular the inferior vena cava and aorta.

36th week of pregnancy

• By the end of the 36th week of pregnancy, the enlarged uterus almost fills the abdominal cavity. The fundus is at the tip of the xiphoid, which is pushed forward.

• The diaphragm is pressed upward, reducing the vertical diameter of the chest cavity by as much as 4cm.

38th week of pregnancy

• By 38 weeks' gestation, Descent of the fetal head into the pelvic brim

(engagement) leads to slight lowering of the fundus, known as

lightening which causes a change in shape of the abdomen. Women

describe this as ‘the baby dropped’. Descent of the fetal head into the

pelvic brim (engagement) leads to slight lowering of the fundus,

known as lightening which causes a change in shape of the

abdomen. Women describe this as ‘the baby dropped’. When this

occurs breathing becomes easier and heartburn occurs less

frequently but the increased pressure on the bladder may lead to

urinary frequency. As pressure increases in the pelvis constipation

may occur and as the pelvic ligaments are stretched more, low

backpain may be experienced.

The cervix

• Within 1 month of conception, the cervix becomes softer and

cyanosed due to oedema and increased vascularity .

• The glands of the cervix undergo such marked hypertrophy and

hyperplasia. The endocervical mucosal cells produce copious

amounts of a tenacious mucus resulting in the development of an

antibacterial plug in the cervix. In the last 6 weeks of pregnancy, the

cervix undergoes many changes (‘ripening’) in preparation for

expelling the fetus. Cervical thinning, softening and effacement can

be readily detected on vaginal examination. This process causes the

expulsion of the mucus plug as a bloody show at the onset of labour.

There are controversies around when cervical shortening occurs

The vagina

• During pregnancy, increased vascularity and hyperaemia develop in the

skin and muscles of the perineum and vulva with softening of the

underlying connective tissue. Increased vascularity affects the vagina and

results in the violet colour characteristic of Chadwick's sign.

• The increased volume of vaginal secretions due to high levels of

oestrogen results in a thick, white discharge known as leucorrhoea .

• In pregnancy, larger amounts of glycogen are deposited in the vaginal

epithelium due to high oestrogen availability.

• Glycogen is metabolized to lactic acid by the Lactobacillus acidophilus,

(‘Döderlein's bacillus’), a normal commensal of the vagina. This leads to

increased vaginal acidity (pH varying from 3.5–6).

Changes in the cardiovascular system

• These complex changes are necessary to:• meet evolving maternal changes in physiological function• to promote the growth and development of the

uteroplacental-fetal unit• to compensate for blood loss at the end of labour.• The key physiological changes that occur are

A summary of the key components and functions of the cardiovascular system including changes in pregnancyComponent Key change in pregnancy

The heart Increases in sizeShifted upwards and to left

Arteries Dramatic systemic and pulmonary vasodilation to increase blood flow

Capillaries Increased permeability

Veins Vasodilation and impeded venous return in lower extremities

Blood HaemodilutionIncreased capacity for clot formation

The key physiological changes that occur cardiac system

INCREASE DECREASEblood volume (WHY)

systemic vascular resistance

cardiac output (30-50%)

blood pressure

stroke volume 10%

Pulmonary vascular resistance

peripheral vasodilatation

colloid osmotic pressure

B. Blood changes: The marked increase in plasma volume associated

with normal pregnancy causes dilution of many circulating factors.

Hematological changes

Increase in :o Oxygen 20-30%o Plasma volume 45-50%o Red cell mass 20-30%o Total blood volume30- 50% o Heart rate 10- 20%o fibrogen concentration (cloating factor)

• Increase total blood volume needed to

meet the demands of the enlarged uterus

provide extra blood flow for placental perfusion

supply the extra metabolic needs of the fetus

provide extra perfusion of kidneys and other organs

counterbalance the effects of increased arterial and

venous capacity

safeguard the mother against adverse effects of

excessive blood loss at birth.

normal changes in heart sounds during pregnancy:

increase loudness of both S1 & S2.

>95% develop systolic murmur which disappears after delivery.

20% have a transient diastolic murmur.

Relative tachycardia

Pregnancy problem due these changes

• Physiological edema• Renin and aldosterone activity are increased by

oestrogens, progesterone and prostaglandins, leading to increased fluid and electrolyte retention.

• Physiological anemia• The total plasma volume is increase in higher

percentage in comparison to RBC which result in hemodilution

• Decrease blood pressure• Increase cardiac output is this lead to decrease arterial blood pressure by 10%, therefore resistance to flow must be decreased. In addition this can be result in decrease in systemic vascular resistance, particularly in the peripheral vessels. The decrease begins at 5 weeks' gestation, reaches a nadir in the second trimester (a 21% reduction) and then gradually rises as term approaches

supine hypotensive syndrome

• The enlarging uterus compresses both the inferior vena cava and the lower aorta when the woman lies in supine position. This reduces venous return to the heart this condition happen in 10% of pregnant women.

• Sign of supine hypotension• hypotension, bradycardia, dizziness, light-headedness. Supine hypotension occurs in around 10% of pregnant womens

Varicosities

• Varicosities develop in approximately 40% of women, and are usually seen in the veins of the legs, but may also occur in the vulva and as haemorrhoids in the anal area. The effects of progesterone and relaxin on the smooth muscles of the vein walls, and the increased weight of the growing uterus all contribute to the increased risk of valvular incompetence. A family tendency is also a factor Some suggestions for alleviating them include: spraying the legs with hot and cold water, resting with the legs elevated and wearing supportive stockings.

Respiratory changes

• Pregnancy is associated with marked changes in

respiratory physiology mediated by biochemical

and mechanical factors. These accommodate the

progressive increase in oxygen consumption of

the enlarging uterus. Normal oxygen consumption

is 250mL/min at rest and increases by 20% in

pregnancy in order to meet the 15% increase in

the maternal metabolic rate

• Changes in pregnancy result in an

overcompensation to this respiratory demand.

The resulting hyperventilation causes the

arterial oxygen tension to increase and arterial

carbon dioxide tension to fall, accompanied by

a compensatory fall in serum bicarbonate. A

mild respiratory alkalosis is therefore normal in

pregnancy.

• Hyperventilation can be extremely

uncomfortable and may lead to dyspnoea and

dizziness. Although it is not usually associated

with pathological processes, care must be

taken not to dismiss it lightly and miss a

warning sign of cardiac or pulmonary disease

(Steinfeld & Wax 2001).

• The shape of the chest changes as diameters increase, by about 2cm, resulting in a 5–7cm expansion of the chest circumference.’

• The flaring of the lower ribs, causes the diaphragm to rise by up to 4cm, its contribution to the respiratory effort increasing with no evidence of being impeded by the uterus.

• These changes are thought to be mediated by the effect of progesterone, which together with relaxin, increases ribcage elasticity by relaxing ligaments. Progesterone also mediates

Respiratory changes

increase O2 demand by 18 %.↑tidal volume with normal respiratory rate 40 % .

↑po2 and ↓pco2 with compensatory ↓HCO3(mild compensated respiratory alkalosis).

Breathlessness due to hyperventilation and elevation of diaphragm.

tissue and oxygen availability to placenta improves.

•ventilatory changes:thoracic anatomy changes.tidal volume increases.vital capacity (maximum amount of air that can be forcibly expired after maximum inspiration) No change.

functional residual capacity decrease.

Breathlessness

• Breathlessness during pregnancy occurs in

approximately 75% of women with exertion and

under 20% at rest.

• This physiological dyspnoea often occurs early in

pregnancy and does not interfere with daily

activities and usually diminishes as term

approaches.

• Distinguishing this physiological dyspnoea from

breathlessness caused by disorders complicating

pregnancy or diseases that might coexist with

pregnancy is essential. It can be alleviated by

maintaining an upright posture and holding hands

above the head while taking deep breaths.

Avoiding excessive exertion is advisable.

Central nervous system

• The pituitary gland increases in size by 30–50% in pregnancy accounting for much of the increased pituitary activity.

• Oestrogen and progesterone readily enter the brain acting on a multitude of nerve cells changing the balance between inhibition and stimulation.

Central nervous system

• Oxytocin neurons are inhibited from releasing the stored oxytocin prematurely through several hormonal mechanisms involving progesterone, oestrogen and opioid peptides. At term, progesterone secretion falls and the inhibitory mechanism modified to allow gradual release of oxytocin in labour followed by a surge at the time of birth.

• Sleep disturbances are a common complaint of pregnancy. Various hormonal and mechanical influences promote insomnia leading to disturbed sleep during pregnancy in most women. With up to 90% of women report frequent night awakenings. Sleep disturbance may increase the labor length and chance of CS delivery.This worsens toward the end of pregnancy and continues to some extent for 3 months postpartum (Hedman et al 2002).

• Interventions include establishing sleep – wake habits, avoiding caffeine, relaxation techniques, massage, heat and support for lower back pain, modifying sleep environment, limiting fluids in the evening and avoiding passive smoking. Sleep medications should be avoided. Some studies have shown that sleep loss in the last few weeks of pregnancy are associated with increased labour length and LSCS rates.

• Pregnant women's sleep patterns are affected by

both mechanical and hormonal influences. These

include nocturia, dyspnoea, nasal congestion,

stress and anxiety as well as muscular aches and

pains, leg cramps and fetal activity.

•  

The urinary tract and renal function

• blood flow increase (60-70%).

• glomerular filtration increased (50%).

• clearance of most substances is enhanced.

• plasma creatinine ,urea,urate are reduced.

• glycoseuria is normal.

UTI in pregnancy

• Progesterone may be involved in the relaxation of bladder

smooth muscle, and in extreme cases, lead to retention of

urine . the above factor can lead to urinary stasis and an

increased risk of urinary tract infection in pregnancy.

Glycosuria provides substrates for bacterial growth and is

therefore another cause of asymptomatic bacteriuria

Urinary frequency

• Urinary frequency (>7 daytime voidings), urgency,

incontinence and nocturia may be experienced. It is

primarily due to the effects of hormonal changes,

hypervolaemia, increased renal blood flow and glomerular

filtration rate although the increased fluid intake during

pregnancy may also play a part. Later in pregnancy it is

likely to be caused by the enlarged uterus, or descent of

the presenting part.

Urinary incontinence

• Urinary incontinence can begin early in pregnancy and the

incidence increases as pregnancy progresses. Stress

incontinence appears to be more common than urge

incontinence although mixed symptoms are frequent.

Women's descriptions of their incontinence range from

mild to ‘terrible’. There is some evidence that pelvic floor

strengthening can prevent incontinence during pregnancy

and in the postpartum period. Normal function usually

returns for most women soon after the birth of the baby

Changes in the gastrointestinal system

• Anatomical and physiological changes take place in each

organ of the gastrointestinal system. Influenced by

oestrogen the gums become highly vascularized and

oedematous. Associated with this is dental plaque,

calculus and debris deposits which increase during

pregnancy. Advanced gingivitis can lead to a specific

angiogranuloma known as epulis.

• Nausea and vomiting is experienced by more than half of all pregnant women. In spite of this, an increase in appetite is common in pregnancy and may be due to the effects of progesterone, which acts as an appetite stimulant

• Taste often changes early in pregnancy. Even before the first missed period, there may be a loss of taste for something usually enjoyed.The development of cravings or aversions to food is also often reported.

• Pica, the persistent craving and compulsive consumption of non-food substances is poorly understood.

• Abdominal distension and a ‘bloated’ feeling occur when

nutrients and fluids remain in the intestinal tract for longer,

particularly in the third trimester due to the prolonged

transit time. Increased flatulence may also occur due to

decreased motility and pressure of the uterus on the

bowel

Constipation

• Constipation occurs because progesterone enhances

absorption of sodium and water in the colon resulting in

smaller stools with lower water content. Iron supplements

may also aggravate constipation. Pregnant women are

advised to consider changing the type of iron supplement

(if used), to increase their intake of bran or wheat fiber

and fluids and to take gentle exercise to alleviate this

problem. Dietary bulking agents may also be helpful

• Haemorrhoids are also fairly common in pregnancy due to both constipation and pressure in veins below the level of the enlarging uterus. Poor support for haemorrhoidal veins in the anorectal area and lack of valves in these vessels can lead to reversal in the direction of blood flow and stasis of blood. Women should be offered dietary advice and if symptoms remain troublesome should consider standard haemorrhoid creams.

• Heartburn or acid reflux into the lower oesophagus during pregnancy occurs up to 85% of women, particularly during the third trimester.

• Frequent or more severe heartburn can interfere with sleep and deter the woman from eating adequately. Lifestyle modifications may be necessary, for example elevating the head of the bed 6 inches, stopping smoking, sleeping on the left side, avoiding reclining for 2–3 hrs after a meal.

• Dietary modifications which may be helpful include eating less fat and more protein, avoiding chocolate and certain drinks such as coffee, citrus juices, tomato products, and alcoholic drinks

Changes in metabolism• The major changes in the utilization of carbohydrate, fat

and protein during pregnancy are closely linked with the functions of the various endocrine glands. The placenta is already secreting hormones that affect metabolism within a few weeks of conception.

• Metabolic changes are essential for the continuous supply of glucose and amino acids for fetal growth as well as for meeting the increased physiological demands of the woman during pregnancy, labour and lactation. Food intake and appetite are increased, activity is decreased, approximately 3.5kg of fat is deposited, energy reserves of approximately 30000kcal are established and 900g of new protein is synthesized by the mother, fetus and placenta.

Maternal weight

• Most of the weight gain during pregnancy is attributable to

the uterus and its contents, the breasts, increases in

blood volume and extracellular fluid.

• Approximately 62% of weight gain consists of water,

which is retained in all systems of the body.

• The recommended pattern for normal weight gain is

approximately 3kg in the first trimester followed by about

0.4kg/week for the remainder of the pregnancy. This

pattern results in approximately 3kg of fat stores

accumulating in the first half of pregnancy, while weight

gained in the second half goes toward the growth of the

fetus and maternal supportive tissues.

• Fetal growth is slow in the first 2 months during

organogenesis but then accelerates rapidly. Maximum

growth rate is achieved between the 4th and 8th month

when the fetus grows at the rate of 5–9% per week. Until

15–16 weeks the placenta is larger than the fetus but by

term the fetus is five to six times heavier than the

placenta. Amniotic fluid increases from 7mL at 8 weeks,

30mL by 10 weeks, 190mL by 16 weeks, to a mean of

about 800mL by 35 weeks

Distribution of average increase in weight• Maternal Uterus• Breasts• Fat• Blood• Extracellular fluid• Fetus• Placenta• Amniotic fluid• Grand total

Skeletal changes

• Back pain occurs in approximately 70% of pregnant

women. The weight of the pregnant uterus and

altered posture (compensatory lordosis) increase

susceptibility which is exacerbated by progesterone

and relaxin causing softening and relaxation of the

ligaments of the pelvis.

Skin changes

• Almost all women note some degree of skin darkening as

one of the earliest signs of pregnancy. While the exact

pathogenesis remains unclear, it is generally attributed to

an increase in melanocyte stimulating hormone,

Hyperpigmentation is more marked in dark-skinned

women and is more pronounced in areas that are

normally pigmented, e.g. areola, genitalia and umbilicus,

in areas prone to friction, such as the axillae and inner

thighs and in recent scars.

• Hair growth has been shown to follow a common pattern in pregnancy. Stimulated by oestrogen, the growing period for hairs is increased in pregnancy so the woman reaches the end of pregnancy with many over aged hairs. This ratio is reversed after birth so that sometimes alarming amounts of hair are shed during brushing or washing. Normal hair growth is usually restored by 6–12 months. Mild hirsutism is common during pregnancy, particularly on the face .

• Actions that may help include reducing damage to the hair by not combing when it is wet, and avoiding hairstyles that pull and stress hair, using shampoos and conditioners that contain biotin and silica. Diet that is high in fruits and vegetables.

Changes in the endocrine system

• prolactin concentration increases markedly but

act after delivery.

• insulin resistance develop.

• corticosteroid concentration increased.

• aldesterone concentration increased.

• angiotensin and renin increased

Hormones produced within uterus

human chorionic gonadotrophin (HCG):it is secreted by trophoblast and can be detected in serum 10 days after conception (RIA).there is high level of circulating HCG in early pregnancy (to provide a suitable environment for implantation and development).to support corpus luteum secretion of oestrogen and progesterone in the first trimester until the placenta becomes able to produce these hormone.the peak level normally occur in the 12th week .

constant level of HCG in late pregnancy is useful in:controlling placental secretion of Estrogen progesterone.suppressing maternal immune system against fetus.•the human chorionic gonadotrophine normally disappear from urine 7-10 days after delivery of placenta.

1. human placental lactogen

It is level increase when the level of HCG start to drop .

HPL has no effect on fetus.HPL effect on :1-the breast:mammary growth during pregnancy.produce of colostrums.milk production lactation.

2-protiens:oHPL stimulate protein synthesis at cellular level.

3-carbohydrate:ostimulate insuline secretion .oinhibit insulin action.4-fat: HPL mobilize fat from body store (lypolysis) lead to increase maternal blood glucose and maternal tissue can not utilze the glucose so the glucose will be available for fetus.

5 .Estrogen

• it is produce by corpus luteum in early pregnancy.

• it is produce by placenta in late pregnancy.

• fetus (liver and adrenal ) provide certain enzyme

which are lack in placenta.

role of estrogen:

estrogen leads to loose connective tissue mainly in

the cervix.

6 .progesterone

• it is production same as estrogen.• it has effect on smooth muscle leads to decrease muscle excitability leads to muscle relaxation mainly in uterus.

Thyroid function

• increase thyroid binding globulin.• increase bound form of T3,T4.•no change in free form of T3,T4.•So no evidence to support what previously thought to be physiological such as increase in size of thyroid gland , increase BMR, body temperature, heart rate.

Diagnosis of pregnancy

•History: symptoms.•Examination: signs.• Investigation : pregnancy test and ultrasound.

• Hegar's (or Goodell's) sign• On bimanual examination, a firm cervix is felt in contrast

with the softer body and compressible, softer isthmus at about 6–8 weeks menstrual age.

• Chadwick's sign• This is the dark purplish red discoloration and congestion

of the vulva and vaginal mucous membranes (Cunningham et al 2005). First detected between the 4th and 8th weeks of pregnancy it reaches its maximum intensity at the 16th week and then persists throughout pregnancy .

• Osiander's sign

• Osiander's sign• This is the stronger and harder vaginal pulsations caused by the greatly increased blood supply and the enlarged uterine artery. This may also occur in the non-pregnant woman due to fibroids and pelvic inflammation.

• Quickening• The first fluttering movements of the fetus are felt around 20 weeks in a first pregnancy and 18 weeks in subsequent pregnancies.

• The Fetal movements can begin to be detected by the examiner around 20 weeks (see Table 14.9).

Sign of pregnancyPresumptiveBreast changes (including feelings of tenderness,fullness, or tingling, and enlargement or darkening of areola)

Hyperprolactinemia induced by tranquilizers Infection Prolactin-secreting pituitary tumor Premenstrual syndrome

Nausea or vomiting upon arising

Gastric disorders Infections Psychological disorders, such as anorexia nervosa

Amenorrhea Anovulation Blocked endometrial cavity Endocrine changes Medications (phenothiazines) Metabolic changes

Frequent urination Emotional stress Pelvic tumor Renal disease Urinary tract infection

Uterine enlargement (in which the uterus can bepalpated over the symphysis pubis)

Ascites Obesity Uterine or pelvic tumor Excessive flatus

Quickening (fetal movement felt by the woman)

Increased peristalsis Cardiopulmonary disorders

Probable Sign

Serum laboratory tests (revealing the presence of

humanchorionic gonadotropin [hCG]

hormone)

Possible cross-reaction of luteinizinghormone (similar to hCG) in some

pregnancytests

Chadwick's sign (vagina changes color from pink to

violet)

Hyperemia of cervix, vagina, or vulva

Goodell's sign (cervix softens) Estrogen-progestin hormonal contraceptives

Ballottement (fetus can be felt to rise against abdominal

wall when lower uterine segment is tapped during

bimanual examination)

Ascites Uterine tumor or polyps

Probable Sign

Braxton Hicks contractions (periodic uterine tightening)

Hematometra Uterine tumor

Palpation of fetal outline (through abdomen)

Subserous uterine myoma

Positive Sign

Sonographic evidence of fetal outline None

Fetal heart audible by Doppler ultrasound None

Palpation of fetal movement (through abdomen)

None