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1、自然生產,楊明智,Factors related to Birth,Passage Birth canalPassenger FetusPower Force of uterine contraction,Pelvic Anatomy,4 bones sacrum,coccyx,two innominate bonesThe true pelvis is bounded above by the promontory and alae of the sacrum,the linea terminalis,and the upper margins of the pubic bones,and
2、the lower by the pelvic outlet.An obliquely truncated,bent cylinder with anterior wall height 5 cm,and the posterior wall,10 cm.Converged side wallsDistance between ischial spines the shortest diameter of the pelvic cavity,Pelvic Joints,Symphysis pubis consists of fibrocartilage,the superior and inf
3、erior(arcuate ligament)pubic ligaments.Sacroiliac joints between the sacrum and the iliac portion of the innominate bones.Relaxation of the pelvic joints results from hormonal change,commenced in early half of pregnancy,and increased during the last 3 m,regressed after parturition.Sacroiliac joint m
4、obility caused by upward gliding movements of the joint,greatest in dorsal lithotomy position,and may the diameter of the outlet by 1.5 to 2 cm.(Shoulder dystocia),Planes and Diameters of the Pelvis,The plane of the pelvic inlet the superior straitThe plane of the pelvic outlet the inferior straitTh
5、e plane of the midpelvis the least pelvic dimensionsThe plane of greatest pelvic dimension of no obstetrical significance,Pelvic Inlet,4 types in shape gynecoid(50%),anthropoid,android,platypelloid.Most are intermediate type.4 diameters anteroposterior,transverse,and 2 obliquesObstetrical conjugate
6、the shortest distance between promontory and symphysis pubis.Estimated by substracing 1.5 to 2 cm from the diagonal conjugate.True conjugate the A-P diameter of the pelvic inlet,Midpelvis,Plane of the least pelvic dimensions,at the level of the ischial spines.The interspinous diameter,10 cm or so,is
7、 the smallest diameter of the pelvis.The anteroposterior diameter,11.5 cm.The posterior sagittal diameter is around 4.5 cm.,Pelvic Outlet,Consists of two triangles with a common base,a line drawn between the two ischial tuberosities.The apex of the posterior triangle is the tip of the sacrum,the lat
8、eral boundaries are the sacrosciatic ligaments and the ischial tuberosities.The anterior triangle the area under the pubic arch.3 diameters A-P,trans.,posterior sagittal,Pelvic Shapes,Caldwell-Moloy classificationAnterior segment Transverse diameter Posterior segment1.Gynecoid pelvis suited for deli
9、very of most fetuses,50%2.Android pelvis poor prognosis for vaginal delivery3.Anthropoid pelvis AP diameter trans.diameter,1/34.Platypelloid pelvis short AP diameter and wide transverse diameter,3%,Pelvimetry,X-rayComputed tomographyUltrasoundMagnetic resonance,Passenger-Fetus,Fetal attitude-Posture
10、,habitusLie of the fetus-The relation of the long axis of the fetus to that of the motherPresentation-The portion the fetus can be felt through the cervix on vaginal examination.Position-The relation of an arbitrarily chosen portion of the presenting part of the fetus to the right or left side of th
11、e maternal birth canal.For more accurately-Anterior,transverse,posterior,Reasons for the Predominance of Cephalic Presentation,Piriform shaped uterusThe breech and its flexed extremities is bulkier than the cephalic pole and more movable.More crowded amniotic cavity after 32nd week of gestation,Diag
12、nosis of Fetal Presentation and Position,Abdominal palpation Leopold maneuversVaginal examination after the commencement of laborAuscultationImaging studies ultrasonography,plain KUB,CT scan,magnetic resonance imaging,NORMAL DELIVERY,PHYSIOLOGY OF PARTURITION,Structure of Uterus,Corpus:*Myometrium-S
13、mooth muscle cells,matrix.*Endometrium(Decidua)*SerosaCervix:*Endocervical epithelial layer*Fibromuscular layer*Squamous epithelial layer*Collagen and extracellular matrix,Decidua,Derived from endometriumIncreased&enlarged stromal cells,glands,and blood vessels.Decidua basilis-Spiral arteries,venous
14、 lake Decidua capsularis Decidua vera(parietalis)Function-Establishment of pregnancy-Immunologic barrier-Secrete prolactin,relaxin,PG,receptors for hormones,Cervix of Uterus(1),Retained the product of conceptionMuscular fibers-Come from the corpus Collagen fibers-Increased uterine tension Glycosamin
15、oglycans-Firm consistencyCervical ripening-Taking place during the last weeks of gestation-Glycosaminoglycans,dermatan sulfate and chondroitin are replaced by hyaluronic acid-soft consistency and distensible,Cervix of Uterus(2),Cervical ripening(cont)-Promoted by relaxin(?)and estrogen-Inhibited by
16、progesterone-Accelerated by 1.Metreurynter(balloon traction)2.Laminaria rod 3.Polyvinyl alcohol sponge+MgSO4(?)4.Dehydroepiandrosterone(DHEA)(JPN)5.Prostaglandin E2 local application 6.Relaxin(Porcine relaxin)(?),Gap Junctions,Cell-to-cell contactPores between the cytoplasms of the two cellPermittin
17、g rapid transmission of electrical impulses and chemical signals from one cell to the next.Absent throughout pregnancy until term or preterm laborProgesterone,NSAID prevents formationEstrogen,PGE2,thromboxanes stimulate gap junction formation,Excitation-Contraction,Intracellular free Ca ion is low.T
18、he level of free Ca ion can be raised by*Concentration gradient influx*Voltage-dependent Ca ion channels*Receptor-operated Ca ion channels*Released from intracellular stores,Physiology of Labor,Neural Mechanism-No influence on myometrial function during parturitionHormonal factors-No direct effect o
19、n contractility but exert a regulatory influence-by way of synthesis of proteins,receptors,phospholipids,and prostaglandin precursors,Relaxing Hormones,Catecholamines-Act on alpha-and beta-receptors.Estrogens(?)stimulate alpha-receptor formation.Progesterone enhances beta-receptors dominanceEpinephr
20、ine-Endogenous beta-agonistBeta-blocker-Uterine contractility,Relaxing Hormones(2),Relaxin-Produced by corpus luteum in pregnancy and is found in decidua and placenta.Its importance in human parturition is not clear yet.,Oxytocic Hormones,Prostaglandin EAlpha-adrenergic neurotransmitters Prostagland
21、in FThromboxane A,OxytocinAngiotensin IIVasopressinBradykinin,Oxytocin,Great potency for uterine contractionOxytocinasePulsatile secretory patternAction on uterine myometrium Stimulate PLC(phospholipase C)-hydrolysis of phosphatidylinostitol in decidua-mobile free arachidonic acid-prostaglandin synt
22、hesis*Increase intracellular Ca ion conc.,Oxytocin Receptors,Present in both myometrium and endometrium.Estrogen and uterine distension-increase oxytocin receptorsProgesterone inhibits the formation of receptors(in animal).The receptor increased throughout pregnancy*At term-80 to 100 fold higher*Hig
23、hest in early labor*In preterm labor-2 to 3 times higher,Prostaglandins,PGE2,PGF2,PGI2,thromboxanePGE2 is 10 times as potent as PGF2.PGF2 is the main prostaglandin released during labor.Action on myometrium-*Increase intracellular free Ca ion-Opening calcium channel-Release Ca from intracellular ves
24、iclesReceptors-Significant lower during pregnancy.PGE2 has higher affinity.,PG and Human Parturition,PG increases strikingly during labor in amniotic fluid,maternal blood,urine and in intrauterine tissues.PG(E2,F2)evoke myometrial contraction at any stage of pregnancy.Administration routes-Oral,intr
25、aamniotic instillation,IV,or vaginal suppository.Inhibition of PG synthesis-Prolongation of pregnancy or stop labor,NORMAL DELIVERY,NORMAL LABOR,Lightening,Occurs a few weeks before the onset of labor-Reduced fundosymphysis distance(FSD)Change in abdominal shapeFetal head descentConsequence of the d
26、evelopment of a well-formed lower uterine segmentAmniotic fluid volume reduced.,Sings of Labor,Passage of the mucus plugBloody showIntermittent low back painIntermittent low abdominal painRupture of the membranes,True Labor,False laborDefinition of labor Uterine contractions that bring about demonst
27、rable effacement and dilatation of the cervix.Dublin Painful uterine contractions accompanied by any one of the following:1.Ruptured membranes,2.Bloody show,3.Complete cervical effacement.In US-Intact membranes with cervical dilatation of 3 to 4 cm or greater-onset of labor commences with the time o
28、f admission.,False labor vs.True labor,Causes of Labor Pain,Hypoxia of the contracted myometriumCompression of nerve ganglia in the Cx and the lower uterus by the interlocking muscle bundlesStretching of the Cx during dilatationStretching of the overlying peritoneum,Characteristics of Labor,Involunt
29、aryPacemaker-A group of highly excitable myometrial cells near the uterotubal junction-propagate by gap junctionsFerguson reflex-Mechanical stretching the cervix enhancing the uterine activityDiminishing intervalsDuration-30 to 90 sec/contractionPressure-20 to 60 mmHg,ave.40 mmHg.,Differentiation of
30、 Uterine Activity,Upper segment-Active segment,contracts,retracts and expels the fetus.Myometrial fibers become shorter and thicker.Lower segment-Passive segment,relaxed,dilated and greatly expanded,thinned-out for the passage of the fetus Myometrial fibers become stretched and longer.,Forces Concer
31、ned in Labor,Positive forces*Uterine contractions*Abdominal pressure by rectus muscles*Fundal pressure*Forceps delivery and vacuum extractionResistance*The uterine cervix*The muscles of the pelvic floor,Stages of Labor,First stage-Labor onset to full dilation of cervix(Cx.effacement and dilatation)S
32、econd stage-Full dilatation of cervix to delivery of the infant(Expulsion of the fetus)Third stage-Delivery of the infant to the delivery of the placenta and the fetal membrane(Separation and expulsion of the placenta)Fourth stage-One hour after delivery of the placenta,Lacerations of Birth Canal,1st degree laceration involves the fourchette,perineal skin,and vaginal and vaginal mucous memebranes.2nd degree lacceration 1st+the fascia and muscles of the perineal body3rd degree laceration 2nd+anal sphincter laceration4th degree laceration 3rd+through the rectal mucosa,
