1、AbnormallaborengliAbnormallaborenglishsh异常分娩专题知识异常分娩专题知识Stages of laborThe second stage(the period of expulsion)lasts from complete cervical dilatation till the delivery of the infant The third stage(the placental stage)begins immediately after delivery of the infant and ends with the delivery of th
2、e placentaThe fourth stage is defined as the early postpartum period of approximately 2 hours after delivery of the placenta.During this period the patient undergoes significant physiologic adjustment and must be under close medical controlAbnormallaborenglish异常分娩专题知识2Abnormal labor-dystocia(difficu
3、lt labor)It results when:-anatomic or functional abnormalities of the fetus-abnormalities of the maternal bony pelvis-abnormalities of the uterus and cervix-or combination of these abnormalities interfere with the normal course of laborAbnormal labor describes complications of the normal labor proce
4、ss:slower than normal progress or a cessation of progressAbnormallaborenglish异常分娩专题知识3Abnormal labor(or dystocia)is divided into:-prolongation disorders-arrest disordersAbnormallaborenglish异常分娩专题知识4Patterns of abnormal labor-dystocia:A prolonged latent phaseA latent phase of labor is abnormal when i
5、t lasts 20 hours in primigravid patients 14 hours in multigravid patientsThe causes of such situation:-abnormal fetal position-unripe cervix”-administration of excess anesthesia-fetopelvic disproportion-disfunctional uterine contractionsAbnormallaborenglish异常分娩专题知识5A prolnged latent phase does not i
6、tself pose a danger to the mother or fetus.Some patients who are initially thought to have a prolonged latent phase turn out only to have false labor.Abnormallaborenglish异常分娩专题知识6Patterns of abnormal labor-dystocia:A prolonged active phaseAn active phase is abnormal when it lasts longer than:-12 h i
7、n the primigravid patients-6 h in the multigravid patientsor when the rate of cervical dilatation is less than-1,2 cm/h in primigravid patients-1,5 cm/h for multiparasor when descend of the presenting part is less than-1,0 cm/h for primigravidas-1,5 cm/h for multiparasAbnormallaborenglish异常分娩专题知识7Ca
8、uses of prolonged active phase:-abnormal fetal position-fetopelvic disproportion-excessive use of sedation-inadequate contractions-rupture of fetal membranes before the onset of active laborAbnormallaborenglish异常分娩专题知识8Patterns of abnormal labor-dystocia:Arrest disorders:Secondary arrest of dilatati
9、on:no cervical dilatation for 2 h in any case in the active phase of laborArrest of descend:no descent of the presenting part in 1 h in the second stage of laborAbnormallaborenglish异常分娩专题知识9It occurs when:-the contractions are no longer sufficient to maintain the progress of labor orthe labor arrest
10、s in spite of adequate uterine contractions associated with:-too large fetus-fetal lie or position that prevents progress in labor-too small or abnormally shaped pelvisAbnormallaborenglish异常分娩专题知识10Correct diagnosis and management of abnormal labor requires evaluation of the mechanisms of labor:-the
11、 power(uterine contractions)-the passenger(fetal factors-presentation,size)-the passage(maternal pelvis)Abnormallaborenglish异常分娩专题知识11Evaluation of the power includes:strenght,duration and frequency of uterine contractions-manual palpation of the maternal abdomen during a contraction(subjective eval
12、uation)-external tocography(more objective)-a tocodynamometer is an external strain gauge,which is placed on the maternal abdomen,it records when the uterus tightnes and relaxes but does not directly measure how much force the uterus is generating for a given contraction-internal tocography(the most
13、 objective)-an intrauterine pressure catether is placed into the uterine cavity and it transmits the actual intrauterine pressure to the external strain gauge,which then records duration and frequency as well as the strength of the contractionsAbnormallaborenglish异常分娩专题知识12For cervical dilatation to
14、 occur,each contraction must generate at least 25 mm Hg of pressure.The optimal intrauterine pressure during contraction is 50-60 mm Hg.In generating a normal labor pattern the frequency of contractions is also very important.A minimum three contractions in a 10 minute window is usually considered a
15、dequate.Abnormallaborenglish异常分娩专题知识13During the first stage of labor arrest of labor should not be diagnosed until the cervix is at least 4 cm dilated(before ending the latent phase of labor).During the second stage of labor,the power”include both,the uterine contractile forces and the voluntary ma
16、ternal expulsive efforts(pussing)Abnormallaborenglish异常分娩专题知识14Evaluation of the passengerThis includes:-estimation of the expected fetal weight-clinical evaluation of fetal lie,presentation,position If the estimated fetal weight is 4000 g the incidence of dystocia,including shoulder dystocia or fet
17、opelvic disproportion is greater.Cephalopelvic disproportion is a disparity between the size or shape of the maternal pelvis and the fetal head Abnormallaborenglish异常分娩专题知识15If the fetal head is extended a larger cephalic diameter(32 cm)is presented to the pelvis,therby increasing the possibility of
18、 dystociaA brow presentation(forehead-the largest cephalic diameter is 36 cm)(1/3000 deliveries)typically converts to either a vertex or face presentation,but if persistent,causes dystocia requiring cesarean section.A face presentation also requires cesarean section in most cases,although a mentum a
19、nterior presentation(chin toward mothers abdomen)sometimes may be delivered vaginally.Abnormallaborenglish异常分娩专题知识16 Persistent occiput posterior positions are also associated with longer labors(about 1 hour in multiparous patients and 2 hours in nulliparous patients)Fetal anomalies like hydrocephal
20、y and soft tissue tumors may also cause dystocia.The use of prenatal ultrasound significantly reduces the incidence of unexpected dystocia for these reasons.Abnormallaborenglish异常分娩专题知识17Evaluation of the passageMeasurements of the bony pelvis are relatively poor predictors of successful vaginal del
21、ivery.It depends on the inaccuracy of these measurements as well as case-by-case differences in fetal accomodation and mechanisms of labor.Only in rare cases,when the pelvis is completely contracted”(the pelvic diameters are very small)manual evaluation of the diameters of the pelvis can predict tha
22、t the fetus will not passage the birth canal.Abnormallaborenglish异常分娩专题知识18In some cases the X-ray or computed tomographic pelvimetry can be helpful,but the best test of pelvic adeqacy is the progress or lack of progress of descending of the fetal presenting part in the birth canal.Except the bony p
23、elvis,there are soft tissues causes of dystocia,such as:-distended bladder or colon,-adnexal mass-uterine fibroidAbnormallaborenglish异常分娩专题知识19Management of abnormal laborAugmentation of labor is the stimulation of uterine contractions that began spontaneously but are either too infrequent or too we
24、ak,or both.Induction of labor is the stimulation of uterine contractions before the spontaneous onset of labor,with the goal of achieving delivery.Abnormallaborenglish异常分娩专题知识20Stimulation or induction of labor is usually carried out with intravenous oxytocin(sometimes prostaglandines)administrated
25、by means of metered pump.The incidence of prolongation of the first stage of labor can be minimized by avoiding unnecessary intervention,i.e:labor should not be induced when the cervix is not well prepared or ripe(softened,anteriorly rotated,partially effaced)Abnormallaborenglish异常分娩专题知识21The Bishop
26、 score is used to quantify the degree of cervical ripening and readiness for labor.Abnormallaborenglish异常分娩专题知识22A score of 0 to 4 points is associated with the highest likelihood of failed induction.A score of 9 to 13 points is associated with the highest likelihood of successful induction Inductio
27、n of labor is indicated if the anticipated benefits of delivery exceed the risks of allowing the pregnancy to continueAbnormallaborenglish异常分娩专题知识23Indications Post-term pregnancy Maternal medical problems Pregnancy-induced hypertension Premature rupture of membranes ChorioamnionitisAbnormallaboreng
28、lish异常分娩专题知识24Contraindications Placenta or vasa previa Cord presentation Abnormal/unstable fetal lie Prior two or more cesarean sections Prior classical uterine incision Prior uterine incision of unknown type Active genital herpesAbnormallaborenglish异常分娩专题知识25When the cervix is unripe,Prostaglandin
29、 E2(Prepidil,Propess)is administrated intracervically or to the posterior fornix of the vagina.In the majority of these cases labor begins without the need of oxytocin stimulation.Abnormallaborenglish异常分娩专题知识26If the patient is allowed to rest,one of following will occur:-the conractions can stop,in
30、 which case the patient is not in labor(false labor)-the contractions can become more frequent and intensive,in which case the patient will go into active labor-the contractions may be as before,in which case oxytocine may be administrated to augment the uterine contractionsAbnormallaborenglish异常分娩专
31、题知识28The use of amniotomy(artificial rupture of membranes)is also advocated with prolonged latent phase.After amniotomy the fetal head will provide a better dilating force than would the intact bag of waters.Additionaly there may be a release of prostaglandines,which could aid in augmenting the forc
32、e of contractions.The risk of amniotomy is:-an umbilical cord prolapse(the presenting part should be firmly applied to the cervix)-abruption of the placenta-intrauterine infectionAbnormallaborenglish异常分娩专题知识29In the active phase of labor mechanical factors such as abnormal position or presentation a
33、s well as fetopelvic disproportion must be considered before use of oxytocin.If the woman is tired which results in secondary arrest of dilation,rest followed by augmentation with oxytocin is often effective.Artificial rupture of the membranes is also recommended.Abnormallaborenglish异常分娩专题知识30Risks
34、of prolonged laborMaternal Fetal infection maternal exhaustion lacerations uterine rupture uterine atony with possible hemorrhage asphyxia trauma infection cerebral damageAbnormallaborenglish异常分娩专题知识31Prolonged labor is associated with the passage of meconium into the amniotic fluid and subsequently
35、 the risk of meconium aspiration syndrome(MAS).Fetuses who inhale meconium-stained fluid during labor may suffer this syndrom,which includes both mechanical obstruction and chemical pneumonitis from the meconium material.Pathologic factors include:-atelectasis-consolidation-barotrauma-removal of pul
36、monary surfactant by free fatty acidsAbnormallaborenglish异常分娩专题知识32Amniodilution is a method of intrapartum treatment of meconium-stained amniotic fluid.A normal saline solution is slowly infused through a tube inserted in the uterus,washing meconium-stained fluid out and replacing it with the salin
37、e solution.As the fetal head is delivered,but before delivery of the fetal chest,suctioning of the nasopharynx should be performed.After delivery of the fetus suctioning out of meconium in the deeper parts of respiratory tract(below the vocal cords)must be done.Abnormallaborenglish异常分娩专题知识33Techniqu
38、es of operative delivery include:-obstetric forceps-vacuum extraction-cesarean sectionThe purpose of the forceps maneuver is to:1.augment the forces expelling the fetus when the mothers voluntary efforts in conjunction with uterine contractions are insufficient to deliver the infantand eventually to
39、:2.rotate the fetal head in the birth canal,if it isnt completely rotatedAbnormallaborenglish异常分娩专题知识34Necessary conditions to apply forceps:CervixFully dilated MembranesRuptured Position and station of fetal headKnown and engaged Feto-pelvic disproportionExcluded FetusAliveAbnormallaborenglish异常分娩专
40、题知识35Forceps Classification Outlet forceps-the fetal skull has reached the perineal floor,the scalp is visable between contractions,the sagittal suture is in the anteposterior diameter Low forceps-the leading point of fetal skull is+2 station or more Midforceps-the head is engaged but the leading po
41、int of the skull is above+2 station High forceps-the head is high above inlet and isnt engaged,the leading point of the skull above 0 (not performed in current obstetrics)Abnormallaborenglish异常分娩专题知识36To avoid the potential risk of trauma to both maternal and fetal parts application of obstetric for
42、ceps should be performed by an experienced clinicianAbnormallaborenglish异常分娩专题知识37Before application of the forceps the physician should reassess the fetal position.The neonatologist should be notified in advance,before application of the forceps.Forceps should be applied only after the cervix is co
43、mpletely dilated and if there is no evidence of cephalopelvic disproportion.Forceps sshould be applied only(!)after the biparietal diameter has passed through the inlet,and the skull has passed below the ischial spines.Abnormallaborenglish异常分娩专题知识38After delivery the genital tract and infant should
44、be examined carefully.Potential risks:-lacerations of:the cervix,vagina,perineum,bladder and rectum-injuries of the fetus:intracranial hemorrhage,skull fracture,brachial plexus injury,cephalhematoma,facial paralysis,clavicular fractureAbnormallaborenglish异常分娩专题知识39Vaccum extractionThis maneuver is s
45、imilar to forceps delivery.Its purpose is to augment the forces expelling the fetus when the mothers voluntary efforts in conjunction with uterine contractions are insufficient to deliver the infant.Advantages of the vacuum extractor include:-less force applied to the fetal head-reduced anesthesia r
46、equirements-easier aplication-less perineal trauma-the ability to permit the head to find its path out of the maternal pelvisAbnormallaborenglish异常分娩专题知识40Disadvantages of the vacuum extractor include:-the application of traction only during contractions-limitation of its use only to term infant-pro
47、longed delivery in comparison to forceps deliveryThe head must be engaged and the membranes must be ruptured.There is no danger of catching vaginal mucosa or cervical tissue between the vacuum and the fetal head.Traction should be applied during the contraction with the mother bearing down.A safety
48、feature of the vacuum cup is its inability to remain on the fetal head during excess traction which may occur during forceps delivery.Abnormallaborenglish异常分娩专题知识41Cesarean sectionAbout 20-25%of gravidas are now delivered by cesarean section.Appropximately two-thirds of these procedures are perforem
49、d after the onset of labor.Abnormallaborenglish异常分娩专题知识42In elective or not very emergency situations such as -abnormal presentation-placenta previa without bleeding-large fetus-abnormal pelvis-some maternal diseases-prolonged labor-begining of fetal depresiontransverse abdominal incision in the low
50、er part of abdomen,just above the pubic bone,is performed(bikini cut).In such situations there is sufficient time to use regional anesthesia which allows the mother to be awake without feeling pain(spinal block or an epidural catheter).Abnormallaborenglish异常分娩专题知识43In emergency situations such as:-f
