labor part two
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Labor: Part II
by La Lura White MDMaternal Fetal Medicine
Labor: Part II• Mechanics of Labor
• Progress in labor is a result of the interactions between three factors:
• Power: adequacy of contractions.
• Passage: fit between fetal skull and maternal pelvis.
• Passenger: fetal size, position and presentation.
Labor: Part II
• Powers:
• Forces generated by uterine musculature contractions
• Depend on frequency, intensity and duration
• Assess with palpation
• Intra-uterine pressure catheter may assist in direct measurement and calculation of uterine contractility
Labor: Part II• What is adequate uterine activity?
• 3-5 contractions in 10 minutes seen in 95% patients in spontaneous labor at term
• 7 contractions in 15 minutes (active management of labor protocols usually with pitocin support)
• Montevideo units= (average strength of contractions in millimeters of mercury) X (number of contractions in 10 minutes) ; need intrauterine pressure monitor
200-250 units defines adequate labor, but the ultimate measure of uterine activity is clinical, it is the patient progressing in labor
Labor: Part II
70mmhg + 60mmhg + 55mmhg = 185 MVU’s
Center for experimental learning, Quillen College of Medicine, East Tennessee State University
Labor: Part IIPassenger:
• Leopold: Initiated in late 3rd trimester office or triage evaluation in assessment fetal presentation
• Maneuver I:
• Stand facing the patient
• Palpate the fundus with the fingertips of both hands and outlining its shape
• This should allow the identification of the fetal parts in the upper pole (fundus) of the uterus
Labor: Part II
• Maneuver II:
• Place the hands at either side of the maternal abdomen.
• Hold one steady while and feel the opposite edge of the uterus with the other
• Then alternate
• With this maneuver, you should be able to on which side the fetal back lies and on which side the fetal parts lie
Labor: Part II
• Maneuver III:
• Using one hand, grasp the presenting part between the thumb and fingers, on the lower abdomen, just a few centimeters above the symphysis pubis.
• This allows further assessment of the presenting part and its engagement.
Labor:: Part II
• Maneuver IV:
• Similar to the first maneuver but face the opposite direction, towards the patient’s pelvis
• Place the palms of both hands on either side of the lower maternal abdomen, fingertips facing toward the pelvic inlet.
• Identify the fetal parts in the lower pole of the uterus.
Labor: Part II
Labor: Part II
• Presentation: fetal part that directly overlies the pelvic inlet
• Normal and abnormal presentations
http://www.naturalhealthtutoring.com/wp-content/uploads/2010/04/breechpresentation.jpg
Labor: Part II
• Lie: longitudinal axis of fetus in relation to longitudinal axis of uterus• Can be longitudinal transverse cephalic or breech oblique ( between longitudinal and transverse)
http://womanhealthsimplified.com/Childbirth_and_labor.html
Labor: Part II• Attitude: position of the head with regard to fetal spine• Complete flexion best position, presents the smallest
diameter of cephalic presentation, suboccipitobregmatic diameter (9.5cm.) to pelvic inlet
A--Complete flexion. B-- Moderate flexion. C--Poor flexion. D—Hyperextension (military)
Labor: Part II• Position: relationship of a nominated site of presenting
part to a denomonating location on internal pelvis
• For vertex presentations, the occiput is used in relation to the maternal side
• Identify the posterior fontanelle, it is smaller than the anterior fontanelle
Labor: Part II
• ROT--------------------------------------------------------LOT--------
Maternal Anterior
Maternal Posterior
OA
OP
ROP
ROA LOA
LOP
Labor: Part II
• OA:occiput anterior position OP: occiput posterior• LOT: left occiput transverse ROT: right occiput transverse• LOA: left occiput anterior ROA: right occiput anterior• ROP:right occiput posterior LOP: left occiput posterior
Lippincott Manual of Nursing Practice
Labor: Part II • Station: measure of descent of presenting part of fetus through birth canal (-4 to +4) to quantify in cm. distance of bony parts from ischial spines, that is midposition or 0 station
Labor: Part II• Passage
• Determine type of maternal pelvis
• Gynecoid: most common, rounded brim, oval shaped inlet, generous forepelvis, diverging mid-pelvic sidewalls, far spaced and blunt ischial spines, broad well-curved sacrum, a rounded sciatic notch and a sub-pubic angle of 90 degree. Best chance for normal vaginal deliver
Labor: Part II• Android: male pattern, heart shaped inlet, a
transverse diameter that is towards the back. narrow forepelvis, side walls converge, making it a funnel shape with a deep cavity and a straight sacrum that’s prominent with a shallow, converging midpelvic sidewalls, more angulated pubic arch
The ischial spines are prominent and the sciatic notch is narrow with increased risk CPD The sub-pubic angle is less than 90 degree. More common in short, heavily built women with a tendency to be hirsute.
Labor: Part II• Anthropoid: exaggerated long oval shape to the
inlet, anteposterior diameter is longer than the transverse.
• The side walls diverge and the sacrum is long and deeply concave. The ischial spines are not prominent and the sciatic notch is very wide.
• There is a limited anterior capacity, with an increased risk risk of direct occipitoanterior or direct occipitoposterior position, but patient usually delivers uncomplicated
• Women tend to be tall, with narrow shoulders.
Labor: Part II • Platypelloid: broad, flat pelvis with exaggerated oval shape inlet . Kidney-shaped brim in which the anteposterior diameter is reduced and the transverse, its largest diameter is increased.
• The side walls diverge, the sacrum flat and cavity shallow. the ischial spines are blunt with wide sciatic notch and the sub-pubic angle. The obstetrical diameter is shortened.
• The fetal head engages with the sagittal suture in the transverse, to allow the bi parietal diameter to pass the narrowest anteoposterior diameter of the brim.
• This may necessitate lateral tilting of the head, known as asynclitism. The fetus usually descends without difficulty.
Labor: Part II• Pelvimetry: Manual assessment of the planes of the
maternal pelvis:
• Pelvic inlet
• Midpelvis
• Outlet
Labor: Part IIPelvic Inlet:
• Anteroposterior (AP) diameter of the inlet:
• Measure the diagonal conjugate: distance from the lower margin of the symphysis pubis to the sacral promontory
• For the obstetric conjugate (the narrowest AP diameter of the inlet): estimate by subtracting 2 cm from the diagonal conjugate
• A pelvic inlet diameter of 12 cm. or greater is adequate for a normal size fetus diagonal conjugate
Labor: Part II• Pelvic Inlet
• Transverse diameter of the inlet cannot be measured directly
• Palpating laterally along the pelvic brim.
• If more than two thirds of the brim can be easily palpated, and especially if the posterior portions of the brim can be felt, it is likely that the patient has a contracted inlet.
• Averages 13 cm.
Labor: Part II• Midpelvis• Transverse diameter of the midpelvis is a plane
that extends from the end of the sacrum to the inferior border of the pubic symphysis
• Examine shape and prominence of ischial spines, blunt (difficult to identify at all), prominent (easily felt but not large) or very prominent (large and encroaching on the mid-plane).
• Assess the shape of the sacrum (curved or straight)
• Palpate width sacrosciatic notch, if the sacrospinous ligament is the breadth of two and half fingers, the sacrosciatic notch is considered adequate.
• Assess measurement between ischial spines, smallest diameter of pelvis >10 cm.
Labor: Part II• A contracted midpelvis has:
• Flat, prominent sacrum with shallow concavity
• Prominent ischial spines
• Narrow interspinous distance.
• Sacrosciatic notch is less than two fingerbreadths wide
• Pubic arch is narrow
• Pelvic sidewalls converge
Labor: Part II• Pelvic Outlet
• Transverse diameter : Estimate the distance
between the ischial tuberosities by placing fist on perineum (greater than 10 cm)
• Palpate the coccyx to determine its orientation and mobility
• Assessing the subpubic angle to be greater than 90 degrees
• Check the convergence or divergence of the pelvic sidewalls
• Evaluate the retro or subpubic angle, , normally, it admits 2 fingers. If it is flattened (platypelloid pelvis) or sharply angulated (android pelvis).
•
Labor: Part II• Fetal Skull
• Bones of the fetal skull:• One occipital bone
posteriorly.
• Two parietal bones bilaterally.
• Two temporal bones bilaterally.
• Two frontal bones anteriorly.
Temporal bones lie anterioposteriorly to parietal bones
Labor: Part II• Sutures of the fetal skull—membranous
spaces between the bones of the fetal skull:• Frontal—between the two frontal bones.
• Sagittal—between the two parietal bones.
• Coronal—between the frontal and parietal bones.
• Lambdoidal—between the back of the parietal bones and the margin of the occipital bone.
Labor: Part II
• Fontanelles of the fetal skull—irregular spaces formed where two or more sutures meet. Sutures and fontanelles allow fetal skull bones to overlap and mold in order to pass through the maternal pelvis.
• Anterior—largest fontanelle; junction of the sagittal, frontal, and coronal sutures—Closes by age 18 to 24 months; “diamond” shaped.
• Posterior—located where the sagittal suture meets the lambdoidal (smaller than anterior)—Closes by 1 year; “triangle” shaped.
Labor: Part II• Diameters of fetal skull
• Suboccipital–BregmaticNape of neck to center of bregma 9.5 cm.
• Submental–BregmaticBelow chin to center of bregma 9.5 cm.
• Mentum–VerticalPoint of chin to above posterior fontanell 14.0 cm.
Labor: Part II
• Basal–Vertical Base of skull to most distant point of vertex 9.0 cm.
• Occipital–Frontal Root of nose to occipital protuberance 11.5 cm.
• Biparietal Between the two parietal eminences * 9.5 cm.
• BitemporalGreatest distance between
two halves of coronal suture 8.5 cm.
Labor: Part II
• Cardinal Movements in Labor: changes in position of fetal head as it passes through the birth canal
• Engagement: passage widest diameter presenting part below plane of pelvic inlet
• Descent: downward passage presenting part through pelvis
• Flexion: secondary to passive resistance against pelvic floor; presents smallest diameter of fetal head (suboccipitobregmatic) for passage
Labor: Part II • Internal Rotation: usually moves transverse to
anterior-posterior; occurs in midpelvis
• Extension: brings base of occiput in contact with inferior margin symphysis pubis once reaches introits
• External Rotation: restitution, fetal head rotates to align with shoulders
• Expulsion: Delivery remainder of fetus
Cardinal Movements
• If we have mastered the information to appropriately manage a patient in labor
• Recognize complications of labor and institute the proper management
• Develop a personal and professional relationship with mother and baby
• ……..Then
……….you have truly become an Obstetrician
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Or you can contact Dr. White for teaching and conference opportunities at:
Second Opinion 2 1-800-219-0713
E-mail info@secondopinion2
Labor: Part II• Terminology
• Gravid: state of pregnancy• Gravida: pregnant female • Parity (para): number of previous successful live births• Nulligravid: a woman who has never been pregnant• Primigravida: a woman who is pregnant for the first time • Multigravida: a woman who has had more than one
pregnancy• Nulliparous: a women who has not carried a pregnancy
beyond 20 weeks of gestation • Embryo: describes the developing offspring during the
first 8 weeks following conception,
Labor: Part II• Fetus: is used from 8 weeks of development until
birth• Engagement : Occurs when the largest diameter of
the presenting part reaches or passes through the pelvic inlet
• Molding: Shaping of the fetal head by overlapping of the cranial bones to facilitate movement through the birth canal during labor.
Labor: Part II
Bibliography:
1) Pritchard JA Mac Donald PC (eds): William’s Obstetrics,16th ed. New York, Appleton-Century-Crogts, 1980.
2) Creasy R.K., Resnik, R., Maternal Fetal Medicine, 6th ed. Saunders Elsvier, 2009.
3) Gibbs, Ronald S.; Karlan, Beth Y.; Haney, Arthur F.; Nygaard, Ingrid E, Danforth's Obstetrics and Gynecology, 10th Edition, Lippincott Williams & Wilkins.
4) Google Images
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