physiology of pregnancy liu wei department of ob & gy renji hospital

Physiology of PregnancyPhysiology of Pregnancy

Liu WeiLiu Wei

Department of Ob & GyDepartment of Ob & Gy

Renji hospitalRenji hospital

Normal PregnancyNormal Pregnancy

• PregnancyPregnancy

The course that the embryo and the The course that the embryo and the fetus grow in the maternal bodyfetus grow in the maternal body

• Stages of pregnancyStages of pregnancy

1.1. Early pregnancy: ≤12 weeksEarly pregnancy: ≤12 weeks

2.2. Mid pregnancy: ≥13 weeks,≤27 weeks Mid pregnancy: ≥13 weeks,≤27 weeks

3.3. Late pregnancy:≥28 weeksLate pregnancy:≥28 weeks

4.4. Term pregnancy:≥37 weeks,<42 weeks Term pregnancy:≥37 weeks,<42 weeks

Formation of EmbryoFormation of Embryo

• FertilizationFertilization

1.1. Place: oviduct (ampulla)Place: oviduct (ampulla)

2.2. ProcessProcess

capacitation → acrosome reaction→ capacitation → acrosome reaction→ penetrate the zona pellucida→ seconpenetrate the zona pellucida→ second meiosis →zygoted meiosis →zygote


• ImplantationImplantation

1.1. requirementrequirement

1)1) Disappear of zona Disappear of zona pellucidapellucida

2)2) Formation of Formation of syncytiotrophoblastsyncytiotrophoblast3)3) Synchronized development of blastoSynchronized development of blasto

cyst and endometriumcyst and endometrium

4)4) Adequate progesterone Adequate progesterone


2.2. ProcessProcess

1)1) morula (day 3) → enter uterine cmorula (day 3) → enter uterine cavity (day 4) → early blastocystavity (day 4) → early blastocyst→ late blastocyst (day 6-7) → i→ late blastocyst (day 6-7) → implantationmplantation

2)2) locationlocation→→ adherence adherence→→ penetra penetrationtion

Development of embryo and fetusDevelopment of embryo and fetus

• DefinitionDefinition

1.1. embryo: embryo: ≤ ≤ 8 weeks8 weeks

2.2. Fetus: Fetus: ≥≥ 9 weeks, human shape 9 weeks, human shape


• Physiology of fetusPhysiology of fetus

1.1. CirculationCirculation

1)1) fetus ←→placenta←→ materfetus ←→placenta←→ mater

2)2) 1 umbilical vein (full of oxygen), 1 umbilical vein (full of oxygen), 2 umbilical artery (lack of 2 umbilical artery (lack of oxygen)oxygen)

3)3) Mixed blood (vein and artery)Mixed blood (vein and artery)


2.2. HematologyHematology

1)1) ErythropoiesisErythropoiesis

From yolk sac: 3 weeksFrom yolk sac: 3 weeks

From liver: 10 weeksFrom liver: 10 weeks

From bone marrow and spleen: terFrom bone marrow and spleen: term (90%)m (90%)

EPO production: 32EPO production: 32ndnd week week


2)2) Fetal hemoglobinFetal hemoglobin

Fetal hemoglobin: early pregnancyFetal hemoglobin: early pregnancy

Adult hemoglobin: 32Adult hemoglobin: 32ndnd week week

Term: fetal type Hb 25%Term: fetal type Hb 25%

3)3) White cellsWhite cells

Leukocytes: 8 weekLeukocytes: 8 week

Lymphocytes (antibody production): 12 Lymphocytes (antibody production): 12 week, thymus and spleenweek, thymus and spleen


3.3. Gastrointestinal tractGastrointestinal tract

1)1) drink amniotic fluid: 4drink amniotic fluid: 4thth month month

2)2) no proteolytic activityno proteolytic activity

3)3) enzymatic deficiencies in liver: enzymatic deficiencies in liver:

bilirubin is not easy to be clear.bilirubin is not easy to be clear.


4.4. KidneyKidney Its function begins at 11-14Its function begins at 11-14thth week week5)5) EndocrinologyEndocrinology6)6) Fetal thyroid: the first endocrine glaFetal thyroid: the first endocrine gla

nd (6nd (6thth week), synthesize thyroxine a week), synthesize thyroxine at 12t 12thth week week

7)7) Fetal adrenal cortex: widen (20Fetal adrenal cortex: widen (20thth wee week), a fetal zone. synthesize steroid hk), a fetal zone. synthesize steroid hormones (E3, liver placenta mater)ormones (E3, liver placenta mater)

PlacentaPlacenta

• StructureStructure

1.1. Primary villusPrimary villus

syncytiotrophoblast cytotrophosyncytiotrophoblast cytotrophoblastblast

2.2. Secondary villusSecondary villus

3.3. third class vilusthird class vilus

fetal capillary enter the stromafetal capillary enter the stroma

PlacentaPlacenta

• FunctionFunction

1.1. metabolismmetabolism

1)1) Exchange of OExchange of O22 and CO and CO22

2)2) Exchange of nutritive factors and waExchange of nutritive factors and wasteste

2.2. DefensiveDefensive

Limited. IgG, virus, drug Limited. IgG, virus, drug

PlacentaPlacenta

3.3. EndocrineEndocrine1)1) HCGHCG2)2) HPLHPL3)3) EE4)4) PP5)5) OxytocinaseOxytocinase6)6) Cytokines and Growth FactorsCytokines and Growth Factors4.4. Immunity toleranceImmunity tolerance

Fetal membranesFetal membranes


chorion and amnionchorion and amnion• AmnionAmnion

A double-layered translucent membraA double-layered translucent membranene

Become distended with fluidBecome distended with fluid

Umbilical CordUmbilical Cord


amnion, yolk sac, one vein, two amnion, yolk sac, one vein, two artery and Wharton jellyartery and Wharton jelly

• LengthLength

30-70cm30-70cm

Amniotic fliudAmniotic fliud

• SourceSource

1.1. exudation of fetal membranes exudation of fetal membranes (early pregnancy)(early pregnancy)

2.2. Fetal urineFetal urine

3.3. Fetal lungFetal lung

4.4. Exudation of amnion and fetal Exudation of amnion and fetal skinskin

Amniotic fliudAmniotic fliud

• AbsordAbsord

1.1. Fetal membraneFetal membrane

2.2. Umbilical cordUmbilical cord

3.3. Fetal skinFetal skin

4.4. Fetal drinkingFetal drinking• FeatureFeature

1000-1500ml at 361000-1500ml at 36thth-38-38thth week (peak), tra week (peak), transparent nsparent →→ slightly turbid slightly turbid

Amniotic FliudAmniotic Fliud

• FunctionFunction

1.1. Protect fetalProtect fetal

move freely, warmmove freely, warm

2.2. Protect materProtect mater

prevent infectionprevent infection

Physiologic changes in pregnant womanPhysiologic changes in pregnant woman

• Genital organsGenital organs1.1. UterusUterus1)1) capacity: 5ml-5000ml.weight: 50g-10capacity: 5ml-5000ml.weight: 50g-10

00g00g2)2) Hypertrophy of muscle cellsHypertrophy of muscle cells3)3) EndometriumEndometrium→→decidua: basal deciddecidua: basal decid

ua, capsular decidua, true deciduaua, capsular decidua, true decidua4)4) Contraction: Braxton HicksContraction: Braxton Hicks5)5) Isthmus uteri: 1cmIsthmus uteri: 1cm→→ 7-10cm 7-10cm


6)6) Cervix: coloredCervix: colored

7)7) Ovary: placenta replaces ovary (10Ovary: placenta replaces ovary (10thth week)week)

8)8) Vagina: dilated and soft, pHVagina: dilated and soft, pH↓↓(anti-b(anti-bacteri bacteria)acteri bacteria)

9)9) Ligaments: relaxedLigaments: relaxed


• Cardiovascular systemCardiovascular system1.1. Heart:Heart: move upward, hypertrophy of cardiac mmove upward, hypertrophy of cardiac m

uscleuscle2.2. Cardiac Output Cardiac Output increase by 30%, reach to peak at 32increase by 30%, reach to peak at 32ndnd – –

3434thth week week3.3. Blood pressureBlood pressure early or mid pregnancy Bpearly or mid pregnancy Bp↓.↓.late pregnalate pregna

ncy Bp↑ .Supine hypotensive syndromency Bp↑ .Supine hypotensive syndrome


• HematologyHematology1.1. Blood volumeBlood volume1)1) Increase by 30%-45% at 32Increase by 30%-45% at 32ndnd –34 –34thth (peak) (peak)2)2) Relatively dilutedRelatively diluted2.2. CompositionComposition1)1) Red cellsRed cells Hb:130Hb:130→→110g/L, HCT:38%110g/L, HCT:38%→→ 31%. 31%.2)2) White cells: slightly increaseWhite cells: slightly increase3)3) Coagulating power of blood: Coagulating power of blood: ↑↑ 4)4) Albumin: Albumin: ↓,↓,35 g/L35 g/L


• The Respiratory systemThe Respiratory system

1.1. R rate: slightly R rate: slightly ↑↑

2.2. vital capacity: no changevital capacity: no change

3.3. Tidal volume: Tidal volume: ↑↑ 40% 40%

4.4. Functional residual capacity:Functional residual capacity:↓↓

5.5. OO22 consumption: consumption: ↑↑ 20% 20%


• The urinary systemThe urinary system1.1. KidneyKidney1)1) Renal plasma flow (RFP):Renal plasma flow (RFP):↑↑35%35%2)2) Glomerular filtration rate (GFR):Glomerular filtration rate (GFR):↑↑ 5 5

0%0%2.2. UreterUreter Dilated (PDilated (P↑↑))3.3. BladderBladder Frequent micturationFrequent micturation


• Gastrointestinal systemGastrointestinal system

1)1) Gastric emptying time is Gastric emptying time is prolongedprolonged→→ nausea. nausea.

2)2) The motility of large bowel is The motility of large bowel is diminished diminished →→ constipation constipation

3)3) Liver function: unchanged Liver function: unchanged


• EndocrineEndocrine1.1. Pituitary (hypertrophy)Pituitary (hypertrophy)1)1) LH/FSH: LH/FSH: ↓↓2)2) PRL:PRL:↑↑3)3) TSH and ACTH:TSH and ACTH:↑↑2.2. ThyroidThyroid1)1) enlarged (TSH and HCGenlarged (TSH and HCG↑↑))

2)2) thyroxinethyroxine↑↑ and TBG and TBG↑↑ →→ free T free T33 T T44 u unchangednchanged

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physiology of pregnancy liu wei department of ob & gy renji hospital

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early pregnancy

late pregnancy

mid pregnancy

term pregnancy