Normal Pregnancy

Chapter3 Normal pregnancy

Wang Fuling

一、 Pregnancy physiology  Pregnancy

is the maternal condition of

having a developing fetus( 胎儿 ) in the body.

What is pregnancy? Pregnancy is defined as the course of embryo （胚胎） and fetal growth and development in uterine It begain at the fertilization and end the delivery of the fetal and it’s attachment

（一） The fetus 1

Fetus growth and development  2 Fetal physiology

1 、 Fetus growth and development Fertilization is defined as the course of combination of the oocyte and sperm It onset 12h after ovulation usually in ampulla of the oviduct(fallopian tube)

1 、 Fetus growth and development  The

human conceptus from fertilization through the eighth week of pregnancy is termed an embryo from the eighth week until delivery ， it is a fetus.  The estimated age of the fetus calculated from the frist day of the last menstrual period ,assuming a 28-day cycle.

1 、 Fetus growth and development  During

the frist 8 weeks,the term embryo is used to denote( 表示 ) the developing organism because it is during this time that all the major organs are formed .

1 、 Fetus growth and development  After

the eighth week, the word fetus is proper, the growth of the fetus may be described in units of 4 weeks’ gestational age, beginning with the first day of the LMP （ last menstrual period ）

1 、 Fetus growth and development  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( 听诊器 ),movements have been perceives by mother, the uterine fundus is near the level of the umbilicus （脐）

1 、 Fetus growth and development  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 still relatively 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

1 、 Fetus growth and development  32weeks ：

if born at this stage, about 5 of 6 infants survive  36weeks ： the skin has lost its wrinkled appearance, 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

2 、 Fetal physiology Contents:  Circulatory function  Hematology( 血液学 )  Respiratory function  Gastrointestinal function  Renal function  Endocrinology( 内分泌学 )

2 、 Fetal physiology （ 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)

Development of embryo and fetus

2 、 Fetal physiology （ 2 ） Hematology （血液学） Erythropoiesis （红细胞生成） From yolk sac （卵黄囊） : 3 weeks From liver: 10 weeks From bone marrow and spleen ： after 10 weeks

*By10weeks the liver assumes the major role in erythropoiesis, but the spleen and bone marrow gradually take over this function

2 、 Fetal physiology (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

2 、 Fetal physiology (6)Endocrinology •

Fetal thyroid: the first endocrine gland (6th week), synthesize thyroxine at 12th week

•

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

3 、 The placenta ， umbilical cord and amniotic fluid  The

placenta  The umbilical cord  The amniotic fluid （羊水）

（ 1 ） The placenta  Development

of the placenta  Functions of the maternal placental-fetal unit

（ 1 ） The placenta Structure 2. Primary villus （绒毛） 3. Secondary villus 4. third class villus fetal capillary( 胎儿毛细血管 ) enter the stroma 

*1 、 Development of the placenta  Fertilization 3. Place: oviduct (ampulla) 4. Process capacitation → acrosome reaction→ penetrate the zona pellucida→ second meiosis →zygote( 受精卵 )

Implantation 2. requirement • Disappear of •

zona pellucida Formation of syncytiotrophoblast

Synchronized development of blastocyst and endometrium • Adequate progesterone •

1. •

•

Process morula (day 3) → enter uterine cavity (day 4) → early blastocyst→ late blastocyst (day 6-7) → implantation location→ adherence→ penetration

（ 2 ） Functions of the maternal placental-fetal unit  Endocrine

function Human chorionic gonadotropin （ HCG ） Human chorionic somatomammotropin Placental proteins （胎盘蛋白） Estrogen  Metabolitic function  Protective function

Endocrine function Human chorionic gonadotropin(HCG)  It

is a glycoprotein that has biologic and immunologic similarities to luteinizing hormone from the pituitary  H CG is produced by the syncytiotrophoblast of the placenta  This measurement is useful because it can detect pregnancy in all patients on day 11 after fertilization

Endocrine function Human chorionic somatomammotropin(hGS)  hGS is a protein hormone with immunologic and biologic similarities to pituitary growth hormone  It has been suggested that hGS is the “growth hormone”of pregnancy

Endocrine function Placental proteins  PAPP-A,PAPP-B,PAPP-C,PAPP-D  PAPP-D is the hormone hCS

Endocrine function Estrogen  Estrogen production by the placenta is dependent upon precursors reaching it from both the fetal and maternal compartments

Metabolitic function

Protective function

The functions of placenta  Gas exchange  Suply of nutrition  Depletion of fetal product of metabolisn  Defense function Hormone synthesis Human chorionic gonadotropin(HCG) Human placental lactogen(HPL) Pregnancy specific β -glycoprotein(PS β 1G) Human chorionic thyrotropin(HCT) Estrogen, P, Oxytocinase, heat stable alkaline phosphatase(HSAP)

The umbilical cord  The

embryo has a thick embryonic stalk containing 2 umbilical arteries,one large umbilicak vein,the allantois,and primary mesoderm.  At birth long 50-60cm diameter 12cm

The amniotic fluid  In

the first of pregnancy,amniotic fluid volume appears to increase in association with growth of the fetus  Serum osmolality sodium urea creatinine  Average volume 800ml  Gravity 比重 1.008  pH7.2

Amniotic fluid Source: early from serum dialysis

late fron fetal urine Absorse: by fetal membrane, fetal swallowing(500ml/day) Amniotic exchange: between maternal and fetal 400ml/h

Volume of amniotic fluid  8 weeks:5-10ml  10 weeks:30ml  20 weeks:400ml  38 weeks:1000ml

Status of amniotic fluid  pH:7.20  Density:1.007-1.025  Contained: water(98-99%)

inorganic substance organic substance(1-2%)

The amniotic fluid  Cushions

the fetus against severe injury  Provides a medium in which the fetus can move easily  May be a source of fetul nutrients  In esrly pregnancy,is essential for fetal lung development

Amniotic fliud Absord 2. Fetal membrane 3. Umbilical cord 4. Fetal skin 5. Fetal drinking  Feature 1000-1500ml at 36th-38th week (peak), transparent → slightly turbid 

Amniotic Fliud Function 2. Protect fetal move freely, warm 4. Protect mater prevent infection 

The amniotic fluid  34-36

weeks determination of amniotic fluid volume becomes even more complicated because the larger fetus swallows more fluid,upsetting the relationship between fetal size and fluid volume.  38weeks both amniotic fluid and maternal plasma volume decrease.

Maternal physiology during pregnancy  Genital

tract

 Breasts  Cardiovascular

system  Hematologic system  Pulmonary system  Gastrointestinal tract

Genital tract  Uterus  Ovaries  Vagina

and perineum

Uterus

Changes of reproductive system

Uterus Body: become enlargement and soft from 7×5 ×3cm pre-pregnancy to 35×25 ×22cm at term

Volume of uterus cavity: become enlargement from 5ml pre-pregnancy to 5000ml.at term

Weight: be increased from from 50g prepregnancy to 1000g at term

Wall: become thickness and the thickist at midperiod from 1 cm pre-pregnancy to 2-2.5 cm at term

Blood suply:blood flow increased significantly upto 500- 700ml/min,increased 4-6 times and most of blood flow is transported to the placenta(80-85%)

Isthmus: be dialated 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

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.

Vagina and perineum  During

pregnancy,increased vascularity and hyperemia develop in the skin and muscles of the perineum and vulva,and there is softening of the normally aboundant connective tissue of these structure.

Breasts  In

the early weeks,the pregnant woman often experiences tenderness and tingling.  After the second month,the breasts increase in size and delicate veins become considerably larger,more deeply pigmented,and more erectile.  After the first few months,a thick,yellowish fluid,colostrum,can often by expressed from the nipples by gentle massage

Cardiovascular system  Heart  Cardiac

output  Blood pressure

Heart

Changes of the circulation Heart border: become enlargement Heart rate: increased 10-15 beat per min at the late pregnancy

Heart volume: increased 10% at the late pregnancy

Cardiac output Very important for fetal growth and development

Incrased begain 10 weeks and upto the peak at 32 weeks 80ml/bp and keeps the level to the term pregancy

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

Hematologic system  Blood

volume  Blood components  Red blood cells  White blood cells  Clotting factors

Changes of blood system Volume: increased (30-45% ) begain 6- 8 weeks and up to the peak at 32-34 weeks increased about 1500ml including plasma 1000ml and red cell 500ml

Changes of blood component Red cell: reticulocyte increased red cell decreased 3.6×1012(4.2×1012) Hb decreased 110g/L(130g/L)

WBC: neutrophilic granulocyte increased lymphocyte mild increased no change in orther blood cells

Coagulation Hypercoagulability

Factor ⅱⅴⅶ ⅷ Ⅸ ⅹ increased ESR increased significantly upto 100mm/h

Plasma protein albumin decreased

Pulmonary system  Pregnacy

produces anatomic and physiologic changes that affect respiratory performance  Total lung capacity is reduced(4-5%)by the elevation of the diaphragm

Gastrointestinal tract  During

pregnancy,nutritional requirements are increased,and several ,aternal alterations occur to meet this demand

Diagnosis of pregnancy  The

diagnosis of pregnancy is usually made on the basis of a history amenorrhea,an enlarging uterus,and a positive pregnancy test

Diagnosis of the first-trimester pregnancy  History

and symptoms

 Signs  Assistant

examination

History and symptoms  Amenorrhea  Morning

sickness  Bladder frequency

Signs  Changes

in the genital organs  Changes in breasts  Mastodynia  Enlargement  Linea nigra

Assistant examination  Pregnancy

test  Ultrasound examination  Increased basal body temperature

Diagnosis of the second and third-trimester pregnancy  Symptoms

and signs  Assostant examination

Symptoms and signs  Uterine

enlargement  Quickening  Fetal heart tones  Palpation of fetus

Assostant examination  20-30weeks

measurement of fetal biparietal diameter is used  After 30 weeks the accuracy of measurement by ultrasound is much less

Pregnancy monitoring  Perinatal

period I 28weeks of completed gestation to the frist 7days of life  Perinatal period II 20weeks of gestation through 27days of life

Prenatal care  Initial

office visit  Subsequent visits  Untrition in pregnancy

Initial office visit  History  Physical

examination  Laboratory tests

History  Present

pregnancy  Previous pregnancy  Medical history  Surgical history  Family history

Physical examination  General

examination  Pelvic examination

Pelvic examination  Pelvic

soft tissue  Bony pelvic  Cervical pelvic

Bony pelvic  Pelvic

inlet  Midpelvis  Pelvic outlet

Laboratory tests  Blood

screening  Genetics testing  Urine testing

Subsequent visits  The

standard schedule for prenatal office visits 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 by Leopold’s maneuvers  Fetul heart tones

Untrition in pregnancy A

balanced diet  Iron,folic acid,calcuim,zinc

Fetal assessment  Assessment

of prenatal diagnosis  Assessment of fetal well-being  Fetal maturity tests  Fetal distress

Assessment of prenatal diagnosis  Ultrasound  Amniocentsis  Chorionic

villus sampling  Fetal blood sampling

Assessment of fetal well-being  Fetul

monitoring techniques  Fetul heart rate interpretation

Fetal maturity tests  Lecithin:sphingomyelin  Phosphatidylglycerol  Foam

stability index

ratio

Fetal distress 

  

Undulating baseline-alternating tachycardia and bradycardia with wide swings,often with reduced varibility in between Severe bradycardia-fetual heart rate below 100bpm for a prolonged period of time of at least 10minutes Tachycardia with diminished variability unrelated to drugs Tachycardia associated with additional nonreassuring periodic patterns such as late decelerations or variable decelerations with late recovery-with careful interpretation,FHRpatterns can be a useful screening test for acidemia and hypoxemia

Disorders of amnionic fluid volume  Normally,amnionic

fluid volume increases to about 1L,or somewhat more by 36 weeks,but decreases thereafter  Postterm,there may be only 100 to 200ml or less