Chapter 3 Normal Pregnancy

8/14/2019 Chapter 3 Normal Pregnancy

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Wang Fu-ling

Chapter3 Normal pregnancyChapter3 Normal pregnancy


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Pregnancy physiology

Pregnancy is the maternal condition of

having a developing fetus( ) in the

body.


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What is pregnancy?What is pregnancy?

Pregnancy is defined as the course of

embryo and fetal growth

and development in uterine

It begain at the fertilization and end thedelivery of the fetal and its attachment


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The fetusThe fetus

1 Fetus growth and development

2 Fetal physiology


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11 Fetus growth and developmentFetus growth and development

Fertilization is defined as the course of

combination of the oocyte and sperm

It onset12h after ovulation usually in

ampulla of the oviduct(fallopian tube)


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The human conceptus from fertilization

through the eighth week of pregnancy is

termed an embryo from the eighth weekuntil delivery it is a fetus.

The estimated age of the fetus calculated

from the frist day of the last menstrualperiod ,assuming a 28-day cycle.


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During the frist 8 weeks,the term embryo is

used to denote( ) the developing

organism because it is during this time thatall the major organs are formed .


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After the eighth week, the word fetus is

proper, the growth of the fetus may be

described in units of 4 weeks gestationalage, beginning with the first day of the

LMP

last menstrual period


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8weeks: the organs are beginning to form

12weeks: the fingers and toes have nails,and the

external genitalia may be recognizable 16weeks :the sex is discernible as male or female

20weeks :heart tones may often be detected by

stethoscope(

),movements have beenperceives by mother,the uterine fundus is near the

level of the umbilicus


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24weeks some fat is beginning to be deposited

beneath the wrinkled skin,viability is reached by

the 24th week,but survival at this stage is stillrelatively rare

28weeks the lungs are now capable of

breathing,but the surfactant content is low;survival

is possible in level II or level III neonatal centers


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32weeks if born at this stsge,about 5 of 6

infants survivie

36weeks the skin has lost its wrinkledappearance,the chances for survival are good

40weeks the head has a maximal transverse

diameter of 9.5cm. The average fetus

,therefore,requires cervical dilatation of almost

10cm before it can descend into the vagina


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22 Fetal physiologyFetal physiology

Contents:

Circulatory function

Hematology( )

Respiratory function

Gastrointestinal functionRenal function

Endocrinology( )


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1 Circulatory function

2) fetus placenta mother

3) Umbilical cord: 1 umbilical vein (full of

oxygen), 2 umbilical artery (lack of

oxygen)

4) Mixed blood (vein and artery)


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Development of embryo and fetusDevelopment of embryo and fetus


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2 HematologyErythropoiesis

From yolk sac : 3 weeks

From liver: 10 weeks

From bone marrow and spleen after 10 weeks

*By10weeks the liver assumes the major role inerythropoiesis,but the spleen and bone marrowgradually take over this function


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(3) Respiratory function

gas exchange in the fetus occurs in the

placenta

(4) Gastrointestinal tract

No truly function until after birth

(5) Kidney

Its function begins at 9-12th week


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(6)Endocrinology Fetal thyroid: the first endocrine gland (6th

week), synthesize thyroxine at 12th

week

Fetal adrenal cortex consists mainly of a fetalzone that disappears about 6months after birth.


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33 The placentaThe placenta umbilical cordumbilical cord

and amniotic fluidand amniotic fluidThe placenta

The umbilical cord

The amniotic fluid


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11 The placentaThe placenta

Development of the placenta

Functions of the maternal placental-fetal

unit


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11 The placentaThe placenta

Structure

2. Primary villus

3. Secondary villus

4. third class villus

fetal capillary(

) enter thestroma


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*1 Development of the placenta

Fertilization

3. Place: oviduct (ampulla)

4. Process

capacitation acrosome reactionpenetrate the zona pellucida second

meiosis zygote( )


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Implantation

2. requirement

Disappear of zonapellucida

Formation ofsyncytiotrophoblast

Synchronized development of blastocystand endometrium

Adequate progesterone


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1. Process

morula (day 3) enter uterine cavity

(day 4) early blastocyst lateblastocyst (day 6-7) implantation

location adherence penetration


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22 Functions of the maternalFunctions of the maternal

placental-fetal unitplacental-fetal unit

Endocrine function

Human chorionic

gonadotropin HCG

Human chorionic somatomammotropin

Placental proteins

Estrogen

Metabolitic function

Protective function


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Endocrine functionEndocrine function

Human chorionic gonadotropin(HCG) It is a glycoprotein that has biologic and

immunologic similarities to luteinizing hormonefrom the pituitary

H CG is produced by the syncytiotrophoblast ofthe placenta

This measurement is useful because it can detectpregnancy in all patients on day 11 afterfertilization


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Human chorionic somatomammotropin(hGS)

hGS is a protein hormone with

immunologic and biologic similarities topituitary growth hormone

It has been suggested that hGS is the

growth hormoneof pregnancy


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Placental proteins

PAPP-A,PAPP-B,PAPP-C,PAPP-D

PAPP-D is the hormone hCS


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Estrogen

Estrogen production by the placenta is

dependent upon precursors reaching it fromboth the fetal and maternal compartments


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Metabolitic functionMetabolitic function

The primary function of the placenta is the

transport of oxygen and nutrients to the fetus and

the reverse transfer of CO2(carbon dioxide), urea,and other catabolites back to the mother.

These compounds are required for the synthsis of

new tissues,eg,amino acids vitamins and so on.

Substances such as certain maternal hormones,

which may modify fetal growth.


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Protective functionProtective function

The placental membranes are often referred

to as a barrier to fetal transfer, but there

are few substances(eg, drugs) that will notcross the membranes at all.


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22 The umbilical cordThe umbilical cord

In the early stages, the embryo has a thick

embryonic stalk containing 2 umbilical

arteries,one large umbilical vein,the allantois ,and primary mesoderm( ).

At birth the mature cord : long 50-60cm

diameter 12mm

A long cord is defined as more than 100cm and a

short cord as less than 30cm.


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33 The amniotic fluidThe amniotic fluid

In the first of pregnancy,amniotic fluid

volume appears to increase in association

with growth of the fetusAverage volume 800ml


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Amniotic fluidSource: early from serum dialysis( )late from fetal urine

Absorb: by fetal membrane, fetal

swallowing(400-500ml/day)

Umbilical cord

Fetal skin

Amniotic exchange: between maternaland fetal 400ml/h


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Volume of amniotic fluid

8 weeks:5-10ml

10 weeks:30ml

20 weeks:400ml

38 weeks:1000ml

Note: After 38weeks, both amniotic fluid

and maternal plasma volume decrease.


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Status of amniotic fluid

pH:7.20

Density:1.007-1.025

Contained: water(98-99%)

inorganic substance( )

organic substance(1-2%)


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The functions of amniotic fluidThe functions of amniotic fluid

Cushions the fetus against severe injury

Provides a medium in which the fetus can moveeasily

Warm

May be a source of fetal nutrients

In early pregnancy,is essential for fetal lung

development Protect mother

Prevent infection


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44 Maternal physiology duringMaternal physiology during

pregnancypregnancyThe physiologic,biochemical,and anatomic

changes that occur during pregnancy are

extensive and may be systemic or local.Those maternal adaptation maintain a

healthy environment for the fetus.


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Content:Content:

Genital tract

Breasts

Cardiovascular system

Hematologic system

Pulmonary system

Gastrointestinal tract


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11 Genital tractGenital tract

Uterus

OvariesVagina and perineum


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Changes of uterus

Body: become enlargement and soft

from 75 3cm pre-pregnancy to

3525 22cm at term

Volume of uterus cavity:

become enlargement from 5mlpre-pregnancy to

5000ml.at term


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Weight:be increased from 50g pre-

pregnancy to 1100gat term

Blood supply:blood flow increased significantly

up to 450-650ml/min,increased 4-6

times and most of blood flow istransported to the placenta(80-85%)


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Isthmus:be prolonged and become soft from

1cm pre-pregnancy a portion of the

uterus after 12 gestational weeks

Cervix:be soft and coloration or stain

secrete amount of mucus avoiding the

uterus cavity suffer from infection


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Changes of ovary Stop ovulation

Corpus luteum formation and maintains for

10 weeks

And the function of corpus luteum is

substituted by the placenta Corpus luteum atretic gradually after 3-4

months gestation.


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Vagina and perineumVagina and perineum

During pregnancy,increased vascularity and

hyperemia develop in the skin and muscles

of the perineum and vulva,and there issoftening of the normally aboundant

connective tissue( ) of these

structure.


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22 BreastsBreasts

In the early weeks,the pregnant woman often

experiences tenderness and tingling.

After the second month,the breasts increase in sizeand delicate veins become visible just beneath the

skin.

After the first few months,a thick,yellowish

fluid,colostrum,can often by expressed from thenipples by gentle massage( )


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33 Cardiovascular systemCardiovascular system

Heart

Cardiac output

Blood pressure


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Heart

Heart border:become enlargement

Heart rate:increased10-15 beat per min at the

late pregnancy

Heart volume: increased10% at the late

pregnancy


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Cardiac outputVery important for fetal growth and development

Increased begin 10 weeks and upto the peak

at32-34 weeks and continuing at this level

until term

Cardiac output increase approximately 40%

during pregnancy


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Blood pressure changes due to

pregnancy

No obvious change in Systolic pressure

Mild decreased in diastolic pressure

Vein pressure

No significantly changes in Upper limb vein

pressure

Lower limb vein pressure increased because of

the disturbance of vein reflux


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44 Hematologic systemHematologic system

Blood volume

Blood components

Red blood cells

White blood cells

Clotting factors


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Changes of blood systemVolume: the average increase in volume at

term is 45-50%. Hypervolemia begins in the frist

trimester,increses rapidly in the second

trimester,and the peakat about the 30th week.


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Changes of blood components

Red cell:the increase in red blood cell mass is about

33%,or approximately 450ml of erythrocytes(

).Since plasma volume increases earlier in pregnancy

and faster than red blood cell volume,after the end of

second trimester( 3 ) :

red cell decreased 3.61012(4.21012)

Hb hemoglobin decreased

110g/L(130g/L)


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WBC(white blood cell):the total blood

leukocyte count increases during normal

pregnancy from a pregnancy level of4300-4500/uL to 5000-12000/uL in the

last trimester.


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Clotting factors:

Duringpregnancy , level of several essential

coagulation factors increase.There are markedincreases in factorI VII VIII IX Xand

XII .


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(5)(5) Pulmonary systemPulmonary system

Pregnacy produces anatomic and

physiologic changes that affect respiratory

performanceTotal lung capacity is reduced(4-5%)by the

elevation of the diaphragm


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(6)(6) Gastrointestinal tractGastrointestinal tract

During pregnancy,nutritional requirements

are increased,and several maternal

alterations occur to meet this demand


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Diagnosis of pregnancyDiagnosis of pregnancy

The diagnosis of pregnancy is usually made

on the basis of a history amenorrhea

,an enlarging uterus,and a positivepregnancy test


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11 Diagnosis of the first-trimesterDiagnosis of the first-trimester

pregnancypregnancy History and symptoms

Signs

Assistant examination


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11 History and symptomsHistory and symptoms

Amenorrhea

It is a fairly reliable sign of conception in

women with regular menstrual cycles.In women with irregular cycles,it is not a

reliable sign. Delayed menses may also becaused by other factors such as emotionaltension,chronic disease,endocrinedisorders,and so on.


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Morning sickness nausea andvomiting :

This common symptom occurs in approximately50% of pregnancies.

It begins at about 6 weeks gestation and disappearsat about 12 weeks gestation in most patients.

It is usually most severe in the morning but canoccur at any time.

The cause is probably rising serum levels of HCG.


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Bladder frequency :It occurs because of increased bladder circulation

and pressure from the enlarging uterus.

It usually disappears after 12 weeks gestation when

the uterus enlarges so much that its no longer a

pelvic organ.


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(2)Signs(2)Signs

Changes in the genital organs

Changes in breasts

A. Mastodynia( )

B. Enlargement

C. Linea nigra


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(3) Assistant examination(3) Assistant examination

Pregnancy test : urine testing

Ultrasound examination

Increased basal body temperature


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Pregnancy test

Sensitive early pregnancy tests measure

changes in levels of HCG.If maternal renal function is normal, urine

values are usually proportionate to serumvalues.

Radioimmunoassay for HCG is a sensitiveand specific test for early pregnancy.


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Increased basal body temperature

Persistent elevation of basal body

temperature over a 3-week period usuallyindicates pregnancy if temperatures have

been carefully charted.


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22 Diagnosis of the second andDiagnosis of the second and

third-trimester pregnancythird-trimester pregnancy

Symptoms and signsAssistant examination


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(1)Symptoms and signs(1)Symptoms and signs

Uterine enlargement

Quickening( )

Fetal heart tones

Palpation( ) of fetus


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Uterine enlargementAt 16 weeks, the uterus is usually at the midpoint

between the pubic and the umbilicus.At 20 weeks ,the uterus is palpable at the

umbilicus.

At 26-34 weeks, fundal height correlates roughly

with the estimated gestational age.But after 36 weeks, the fundal height may

decrease as the fetal head descends into the pelvis.


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Quickening( )The first fetal movement is usually

appreciated at 17 weeks in the averagemultipara and at 18 weeks in

the average primipara( ).


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Fetal heart tones

It may be heard at 20weeks.

The normal fetal heart rate is 120-160beats

per minute.

It is best to palpate the maternal pulse for

comparison.


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Palpation( ) of fetusAfter 20 weeks, the fetal outline can be

palpated through the maternal abdominalwall.


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(2)Assistant examination(2)Assistant examination

Ultrasound examination----ultrasound is

used to measure fetal growth parameters, to

estimate fetal weight, to access fetalanatomy, and to measure amniotic fluid

volume.


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33 Pregnancy monitoringPregnancy monitoring

The perinatal interval is the span of fetaland neonatal life.

The perinatal interval of life may be dividedinto 2 periods:

Perinatal period I :28weeks of completedgestation to the frist 7days of life

Perinatal period II: 20weeks of gestationthrough 27days of life


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Prenatal care(Prenatal care(

))The purpose of prenatal care is to ensure,as

much as possible, an uncomplicated

pregnancy and the delivery of a live healthyinfant.

Mothers and offspring who receive prenatal

care have a lower risk of complications.


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44 Initial office visit(Initial office visit( ))

1 History

2 Physical examination

3 Laboratory tests


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11 HistoryHistory

Present pregnancy The interview should beginwith a full discussion of the symptoms; todetermine the duration of pregnancy, the patient

with regular menses may be able to accuratelycalculate the estimated date of confinement(EDC),using the first day of the LMP(LMP-3months+7days)

Previous pregnancy :eg: events of priorpregnancies provide inportant clues to potentialproblems in the current one.


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Medical history:eg: a history of

cardiovascular gastrointestinal , and

endocrine disorders.Surgical history eg a history of

previous gynecologic surgery

Family history : eg history of diabetesmellitus


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(2)Physical examination(2)Physical examination

General examination( )

Pelvic examination


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General examination(General examination( ))

A complete physical examination must be

performed on every new patient.


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Pelvic examinationPelvic examination

Pelvic soft tissue any pelvic mass should

be described accurately and evaluated by

Ultasound examination.Bony pelvis : pelvic

inlet midpelvis pelvic outlet

Cervical length: average cervical length is3-4cm


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Laboratory testsLaboratory tests

The following laboratory assessments shouldbe performed as early as possible inpregnancg and some of these repeated atleast once between 24 and 36 weeksgestation:

Blood screening

Genetics testingUrine testing


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55 Subsequent visitsSubsequent visits

The standard schedule for prenatal officevisits is:

0-32week:once every 4weeks;32-36weeks:once 2weeks;

36weeks to delivery:once each week

Weight, gain blood pressure, fundal height,findings on abdominal examination byLeopolds maneuvers


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66 nutrition in pregnancynutrition in pregnancy

The pregnant woman should be encouraged

to eat a balanced diet and should be made

aware of special needs for iron, folic acid,and zinc.


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Chapter 3 Normal Pregnancy