37 to 42 weeks - Virginia Commonwealth University · 37 to 42 weeks Oxytocin receptors increasing...
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1 1 Normal and Abnormal Labor John W. Seeds, MD Department of Ob/Gyn Virginia Commonwealth University 2 Physiology of labor 3 Events of labor Contractions Effacement and dilatation of cervix – latent and active phase Rupture of membranes – artificial or natural Second stage descent Delivery – spontaneous or assisted – delivery of placenta – inspection of birth canal 4 37 to 42 weeks Oxytocin receptors increasing Myometrial sensitivity increasing Premature labor 11% (8% 30 years ago) – PPROM – chorio – multiple gestation – medical complications – too young or too old (>35 or <18) Post dates 4% – oligo - placental senescence – meconium – when you gotta go….. 5 Normal Labor 259 to 294 days after first day of LMP Fetus longitudinal, head flexed and down Contraction frequency and intensity build Slow dilatation to 4cm then faster Descent and rotation through pelvis Head delivers by extension Shoulders guided under pubis Body expelled under control 6 Presentation, Position, Lie Presentation – cephalic (96%), breech (3.5%), shoulder (.4%), hand, face/brow (.3%), funic Position – occiput anterior, occiput posterior (10%), occiput transverse (transient?), mentum, sacrum, frontum, etc Lie – longitudinal, transverse, oblique
Transcript of 37 to 42 weeks - Virginia Commonwealth University · 37 to 42 weeks Oxytocin receptors increasing...
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Normal and Abnormal Labor
John W. Seeds, MDDepartment of Ob/GynVirginia Commonwealth University
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Physiology of labor
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Events of laborContractionsEffacement and dilatation of cervix– latent and active phase
Rupture of membranes– artificial or natural
Second stage descentDelivery– spontaneous or assisted– delivery of placenta– inspection of birth canal 4
37 to 42 weeksOxytocin receptors increasingMyometrial sensitivity increasingPremature labor 11% (8% 30 years ago)– PPROM– chorio– multiple gestation– medical complications– too young or too old (>35 or <18)
Post dates 4%– oligo - placental senescence – meconium – when you gotta go…..
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Normal Labor259 to 294 days after first day of LMPFetus longitudinal, head flexed and downContraction frequency and intensity buildSlow dilatation to 4cm then fasterDescent and rotation through pelvisHead delivers by extensionShoulders guided under pubisBody expelled under control
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Presentation, Position, Lie
Presentation– cephalic (96%), breech
(3.5%), shoulder (.4%), hand, face/brow (.3%), funic
Position– occiput anterior, occiput
posterior (10%), occiputtransverse (transient?), mentum, sacrum, frontum, etc
Lie– longitudinal, transverse,
oblique
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•Cephalic•Longitudinal•Flexed
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Lie
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Shoulder or arm presentation
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Occiput presentation
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Brow Presentation
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Face Presentation
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LOA LOP
Longitudinal, cephalic, flexed, occiput to mother’s left and posterior 16
ROA ROT
Longitudinal, cephalic, flexed, occiput to mother’s right and anterior
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Uterine contractionsResting tone 10-15 mmhgRegular vs irregular contractions– Braxton-Hicks
• regular or irregular 20-30 seconds– early labor
• regular, closing interval, 45-60 secondsMontevideo units
• aggregate of amplitude above baseline in 10 minute window
• normal 90-390 Montevideo units18
Contractions and Montevideo UnitsAggregate of amplitude above baseline of contractions in 10 minute window
70 + 35 + 50 = 155 Montevideo units
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EffacementEffacement– third trimester to early labor– shortening of endocervical canal– cervix drawn up to become lower uterine
segment– an inside-out process
• 35mm length at 28 weeks• paper thin when complete• the internal os approaches the external os
– best defined in primagravida20
Dilatation
Dilatation– begins late third trimester– complete at approximately 10cm
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Primagravida
PrimagravidaPrimagravida
Primagravida
Multigravida
Multigravida Multigravida
Multigravida
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Fibrous cervix actually drawn into and becomes lower uterine segment
23Fully effaced and dilated cervix has in part actually become the lower segment of the uterus 24
Stationrelative to ischial spines
Through 1989 + or – 1-3 out of 3 thirds of total distanceAfter 1989 + or – 1-5 out of 5 cm above or below spines
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Stages and phases
First stage 6-10 hrs– latent phase 3-8 hrs
• acceleration phase?– active phase 1-2 hrs
• deceleration phase?Second stage 0-3 hrsThird stage 0- 30minFourth stage? 1-2 hrs
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Cardinal movementsFlexion fetal head on neckDescent through pelvisEngagement BPD through inletInternal rotation head vs levator slingExtension head under pubisExternal rotation head follows shouldersExpulsion body delivered
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OFD
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Engagement when BPD below inlet; assumed if leading edge at spines
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Engagement when BPD below inlet; assumed if leading edge at spines
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Flexion anddescent
Engagement
Internal rotation
Internal rotation
Extension
External rotation
Shoulder delivery
Expulsion of body
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Cardinal MovementsFlexion– flexion of the head on the body is the natural
result of the pressure of contractions pushing the fetus down against resistance.
Descent– the natural result of pressure on the fetus
Engagement– when the BPD has passed the plane of the
inlet; often assumed when the presenting edge of the fetal head has reached the ischiaspines
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Outlet
Mid-plane
The natural path for descent and delivery follows an arc through the pelvis
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Cardinal MovementsInternal rotation– descent of the head against the levator sling naturally
aligns the head to an A-P orientationExtension– in case of the typical OA position, the occiput
naturally follows road of least resistance and extends under symphasis pubis
External rotation– once delivered, head realigns with shoulders that then
rotate to A-P alignment and head followsCheck for nuchal cordSuction nasopharynx
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Cardinal MovementsExpulsion– delivery of body
• shoulders–facilitate anterior delivery under pubis–lift posterior over perineal body
• goals during expulsion–keep spine flexed–keep head down–maintain control of infant
• maintain infant at level of mother and clamp and cut cord in timely fashion
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After delivery, the head reassumes its normal alignment with shouldersthat then follow their own internal rotation with the head following
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Head delivered; shoulders not
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Pressure down more than traction out makes room
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Suprapubic pressure can help
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Arrest and protraction disordersProlonged Latent phase– 14 hours multigravida; 20 hours
primagravidaArrest disorder– 2 hours active phase with no further
dilatation– 1 hour second stage with no descent
Protraction disorder– primagravida active phase <1.2 cm/ hour– multigravida active phase < 1.5 cm/ hour
By the book!
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Long deceleration
No descent
Active phase arrest
Arrest of descent
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Response to Abnormal laborAssessment– quality of labor powers– size of infant passenger– size of pelvis passage
Interventions– time– augmentation– assisted vaginal delivery– cesarean delivery
4470 + 50 + 45 = 165 Montevideo Units
Contractions and Montevideo Units
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InterventionsAugmentation– if labor insufficient– if infant not excessive size– only if pelvis clinically adequate
Assisted vaginal delivery– if criteria met– if considered possible
Cesarean delivery– if above criteria not met– if fetal surveillance non reassuring
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Augmentation of laborOxytocin– nona-peptide – released from posterior pituitary– stimulates uterine contractions– oxytocin receptors increase near term– synthetic version for induction/augmentation– at high doses is anti-diuretic – danger of over stimulation
• fetal ischemia• uterine rupture
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Augmentation
Fetal surveillance reassuringLabor pattern suboptimalStart with low doseContinuous internal monitoringIncrease slowly in small incrementsHold at dose with < 200 MVU’s
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Assisted vaginal deliveryForceps (same for vacuum)– high: fetal head unengaged– mid: head above +2 out of 5– low: +2 out of five or more– outlet:
• head on perineum• scalp visible between contractions• sagittal suture within 45 degrees of A-P
Must meet same criteria for vacuum– never use a vacuum where you wouldn’t use
forceps
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Blade Shank
Lock Handle
Simpson Forcepsshallow bladeseparated shankenglish lockfenestrated or semi fenestrated bladefavored for molded larger head
Pelvic curveCephalic curve
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Types of forceps
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Requirements for assisted vaginal delivery
Fully dilatedMembranes rupturedPosition knownEngaged Adequate pain reliefAdequate pelvisRisk of shoulder dystocia acceptable
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Post partum inspectionPerineum– lacerations
• 10 skin/ mucosa/subcu but not fascia• 20 all of above plus fascia but not
sphincter• 30 all plus sphincter• 40 all plus rectal mucosa• Repair anatomically
VaginaCervix
