Presentation on theme: "District 1 ACOG Medical Student Education Module 2008"— Presentation transcript:
1District 1 ACOG Medical Student Education Module 2008 LaborDistrict 1 ACOG Medical Student Education Module 2008
2LaborLabor is the physiologic process by which a fetus is expelled form the uterus to the outside world.It involves the sequential integrated changes in the uterine decidua, and myometrium.Changes in the uterine cervix tend to precede uterine contractions
3Labor - Mechanics Uterine contractions have two major goals: To dilate cervixTo push the fetus through the birth canalSuccess will depend on the three P’s:PowersPassengerPassage
4Power Uterine contractions Power refers to the force generated by the contraction of the uterine myometriumActivity can be assessed by the simple observation by the mother, palpation of the fundus, or external tocodynamometry.Contraction force can also be measured by direct measurement of intrauterine pressure using internal manometry or pressure transducers.
5Power There is no specific criteria for adequate uterine activity Generally 3-5 contractions in a 10 minute period is considered adequate labor
6Passenger Passenger =fetus Fetal variables that can affect labor: Fetal sizeFetal Lie – longitudinal, transverse or obliqueFetal presentation – vertex, breech, shoulder, compound (vertex and hand), and funic (umbilical cord).Attitude – degree of flexion or extension of the fetal headPositionStation – degree of descent of the presenting part of the fetus, measured in centimeters from the ischial spinesNumber of fetusesPresence of fetal anomalies – hydrocephalus, sacrococcygeal teratoma
7Passage Passage = Pelvis Consists of the bony pelvis and soft tissues of the birth canal (cervix, pelvic floor musculature)Small pelvic outlet can result in cephalopelvic disproportionBony pelvis can be measured by pelvimetry but it not accurate and thus has been replaced by a clinical trial of labor
10The Stages of Labor First Stage Interval between the onset of labor and full cervical dilationTwo phases:Latent phase – onset o f labor with slow cervical dilation to ~4 cm and variable durationActive phase – faster rate of cervical change, cm /hour, regular uterine contractions
11The Labor CurveFirst stage - A: latent phase; B + C + D: active phase; B: acceleration; C: maximum slope of dilation; D: deceleration; E: second stage. Adapted from: Friedman. Labor: Clinical evaluation and management, 2nd ed, Appleton, New York 1978.
12LaborLaborNulliGMultiG1st StageActivephaseDuration6-18 h2-10 hDilation~1 cm/h~1.5 cm/hArrested>2 h>2h2nd Stage0.5-3 h5-30 min3rd Stage0-30 minFreidman’s curve is a good guideline for expected progression in labor and therefore helpful to note abnormal labor patterns.
13Labor Variables associated with longer labors: Electronic fetal monitoringNarcotic useMaternal age >30Ambulation
14Labor – Second StageInterval between full cervical dilation to delivery of the infant.Characterized by descent of the presenting part through the maternal pelvis and expulsion of the fetus.Indications of second stage:Increased maternal showPelvic/rectal pressureMother has active role of pushing to aid in fetal descent.
15Labor – Second StageExamining the fetal head during the second stage may become difficult due to moldingMolding is the alteration of the fetal cranial bones to each other as a result of compressive forces of the maternal bony pelvis.Caput is the localized edematous area on the fetal scalp caused by pressure on the scalp by the cervix.PrimiG – h; mulitG 0-30min
16Labor – Third StageThe time from fetal delivery to delivery of the placentaThree signs of placental separation:Lengthening of umbilical cordGush of bloodFundus becomes globular and more anteverted against abdominal hand
17Labor – Third StagePlacenta is delivered using one hand on umbilical cord with gentle downward traction. Other hand on abdomen supporting the uterine fundus.Risk factor for aggressive traction is uterine inversion.Obstetrical emergency!!Normal duration between 0-30 min for both PrimiG and MultiG
18Labor – Fourth StageRefers to the time from delivery of the placenta to 1 hour immediately postpartumBlood pressure, uterine blood loss and pulse rate must be monitor closely ~ 15 minutesHigh risk for postpartum hemorrhage from:Uterine atony, retained placental fragments, unrepaired lacerations of vagina, cervix or perineum.Occult bleeding may occur – vaginal hematomaBe suspicious with increased heart rat, pelvic pain or decreased BP
19Cardinal Movements of Labor Refers to changes in the fetal head position during its passage through the canal.Seven distinct movements:EngagementDescentFlexionInternal rotationExtensionExternal rotation/restitutionExpulsion
20Cardinal Movements of Labor EngagementPassage of the widest diameter fetal presenting part below the plane of the pelvic inletThe head is said to be engaged if the leading edge is at the level of the ishial spines.
21Cardinal Movements of Labor DescentRefers to the downward passage of the presenting part through the bony pelvisNot steady processGreatest at deceleration phase of first stage and during 2nd stage of labor
22Cardinal Movements of Labor FlexionOccurs passively as the head descends due to the shape of the bony pelvis.Partial flexion occurs naturally but complete flexion usually occurs only in the labor processComplete flexion places the fetal head in optimal smallest diameter to fit through the pelvis
23Cardinal Movements of Labor Internal RotationRotation of the fetal head from occiput transverse to occiput either in anterior or posterior positionOccurs passively due to the shape of the bony pelvis
24Cardinal Movements of Labor ExtensionOccurs when the fetus has descended to the level of the vaginal introitusWhen occiput is just past the level of the symphysis, the angle of the birth canal changes to upward position
25Cardinal Movements of Labor External Rotation/RestitutionAs the head is delivered, it rotates back to its original position prior to internal rotationIt aligns anatomically with the fetal torsoThe release of the passive forces on the fetal head allows it to return to appropriate position
26Cardinal Movements of Labor ExpulsionDelivery of the fetusAfter delivery of the fetal head, descent and intraabdominal pressure by mother brings shoulder to the level of the symphysisDownward traction allows release of the shoulder and the fetus is delivered.
28In Summary Know the different stages of labor Know the labor curve Know the cardinal movements of laborKnow the causes of postpartum hemorrhageThe remaining talk regarding labor, induction, augmentation, surveillance and complications will be discussed in following lectures…