Processes and Stages of Labor

Lecture Five: Processes and Stages of Labor

NURS 2208
T. Dennis RNC, MSN

Objectives

• Discuss factors influencing labor
• Identify parts of the true pelvis and the maternal pelvis
• Identify components of the fetal head
• Discuss fetal lie, attitude, presentation, position, engagement,and station
• Discuss uterine contractions
• Define labor, effacement and dilataion
• Identify proposed causes of labor
• Discuss premonitory signs of labor, false labor and true labor
• Discuss the stages of labor

Four Critical Factors in Labor
(pg. 473)

• Birth Passage
• Fetus
• Primary Forces of labor
• Psychosocial considerations

The Birth Passage
(pg. 473)

• Size of maternal pelvis (diameters of the pelvic inlet, midpelvis, and outlet).
• Type of maternal pelvis
• Ability of cervix to dilate and efface and ability of vaginal canal and the external opening of the vagina (the introitus) to distend

The Bony Pelvis (pg. 132-137, 473)

• Functions to support and protect the pelvic contents and to form the relatively fixed axis of the birth passage.
• Made up of hip bones, the sacrum and the coccyx. Ischial spines serve as a reference point during labor to evaluate descent of the fetal head into the birth canal.
• The true pelvis is divided into three sections: inlet, midpelvis and outlet. Represents the bony limits of the birth canal.

Pelvic Types (pg. 136, 473)

• Gynecoid: Most common female pelvis. Inlet is rounded with AP diameter shorter than transverse. Favorable.
• Android: Heart-shaped. Normal male pelvis. Not favorable.
• Anthropoid: Oval in shape. Outlet capacity is adequate. Favorable.
• Platypelloid: Flat female pelvis. Outlet capacity maybe inadequate. Unfavorable.

Fetus
(pg.474-477)

• Fetal head ( size and presence of molding)
• Fetal attitude ( flexion or extension of the fetal body and extremeties)
• Fetal lie
• Fetal presentation (the body parts of the fetus entering the pelvis in a single or multiple pregnancy)
• Fetal position (relationship to pelvis)
• Placenta (implantation site)

Fetal Head (pg. 474-477)

• Molding: Shaping of the fetal head by overlapping of the cranial bones to facilitate movement through the birth canal during labor.
• Sutures : Membranous spaces between the cranial bones of the fetal skull. Allow for molding of the head and identification of fetal position (on vaginal exam).
• Fontanelles: The intersections of the of the cranial sutures.

Sutures (pg. 474)

• Frontal (mitotic) suture
• Sagittal suture
• Coronal sutures
• Lamboidal suture

Important Landmarks (pg. 474)

• Chin
• Brow
• Anterior fontanelle
• Vertex
• Posterior fontanelle
• Occiput

Fetal Attitude (pg.475)

 

• Refers to the relation of the fetal parts to one another.
• The normal attitude of the fetus is one of moderate flexion of the head, flexion of the arms onto the chest, and flexion of the legs onto the abdomen.
• Deviations can contribute to difficult labor.

Fetal Lie (pg. 475)

• Refers to the relationship of the cephalocaudal axis (spinal column) of the fetus to the cephalocaudal axis of the woman.
• May be longitudinal (parallel) or transverse (at right angles).

Fetal Presentation (pg.475)

• Determined by fetal lie and presenting part.
• May be cephalic, breech, or shoulder.
• Most common is cephalic (Vertex, Military, Brow and face).
• Malpresentations make birth more difficult (breech and shoulder).
• Breech (Complete, Frank and Footling).
• Shoulder (arm, back or abdomen).

Functional Relationships (pg.477-478)

• Engagement: Occurs when the largest diameter of the presenting part reaches or passes through the pelvic inlet. The biparietal diameter is the largest part of the fetal skull to pass through the inlet in the cephalic presentation. Ballotable when free moving above the inlet.

Station (pg.478)

• Station: Refers to the relationship of the presenting part to the ishcial spines.
• The ischial spines as a landmark have been designated as 0 (zero) station.
• Higher is a negative number …lower than spines is a positive number. (ex. -2 or +3).

Fetal Position (pg.478-479)

• Refers to relationship of the landmark of the presenting fetal part to the front (anterior), back (posterior), or sides (left or right) of the maternal pelvis.
• The landmark chosen for vertex presentation is the occiput.
• Three notations are used to describe the fetal position: (ex.)ROA, ROP, ROT, LOA

Forces of Labor (pg.480 )

• Frequency, duration, and intensity of uterine contractions as the fetus moves through the passage (Primary).
• Effectiveness of the maternal pushing effort (Secondary).
• Duration of labor

Contractions

• Are rhythmic but intermittent
• Relaxation allows re-oxygenation of fetus and rest from labor.
• Three phases: Increment, Acme, Decrement
• Frequency
• Duration
• Intensity

Psychosocial Considerations
(pg. 481)

 

• Physical preparation for child birth
• Sociocultural heritage
• Previous childbirth experience
• Support from significant others
• Emotional status

Possible Causes (pg. 482-484)

• Progesterone Withdrawal Hypothesis
• Prostaglandin Hypothesis
• Corticotrophin Hormone Hypothesis
• Myometrial Activity
• Intra-abdominal Pressure
• Musculature in the Pelvic floor

Premonitory Stages of Labor
(pg. 484)

• Lightening
• Braxton Hicks Contractions
• Cervical changes
• Bloody Show
• Rupture of Membranes
• Sudden Burst of Energy
• Weight loss
• Increased Backache
• Other signs (diarrhea, indigestion, vomiting, nausea )

Differences of True and False Labor (pg. 485)

• True labor contractions (ctx) (1) produce cervical dilatation, (2) occur regularly and increase in frequency, duration, and intensity, (3) Usually start in the back and radiate to the abdomen and (4) pain is not relieved by ambulation….exercise may intensify true labor contractions.

Differences of True and False Labor (pg. 485)

• False labor contractions (ctx) (1) do not produce cervical dilatation, (2) do not occur regularly and increase in frequency, duration, and intensity, (3) Usually occur in the lower abdomen and (4) pain may be relieved by ambulation….exercise may decrease false labor contractions.
• False labor is common.

Stages of Labor and Birth
(pg. 486 - 490)

• First Stage: Latent, Active, and Transition
• Second Stage
• Third Stage
• Fourth Stage
• Begins with the beginning of true labor and ends when the cervix is completely dilated at 10 cms. Three phases.
• Latent phase: Contractions are usually mild, SROM (spontaneous rupture of membranes) may occur or AROM, copes well, 1- 4 cms.
• Active phase: 4 -7cms, Fetal descent is progressive.
• Transition phase: 8 - 10 cms, descent increases, contractions stronger, may want to push.

Second Stage (pg. 487-488)

• Begins when the cervix is completely dilated and ends with the birth of the infant.
• Epidural may extend this period.
• Perineum begins to bulge, increased bloody show, head recedes between pushes, crowning occurs.
• Contractions every 2 minutes, strong, 60-90 sec.
• Coping improves usually.

Mechanisms of Labor
(Positional Changes pg. 487-488)

• Descent: head enters the inlet
• Flexion: fetal head flexes with descent
• Internal Rotation: fetal head rotates to fit the widest anteroposterior diameter of the pelvic cavity
• Extension: head extends
• Restitution: head turns to one side
• External Rotation: head turns farther to side
• Expulsion: head then body is born

Third Stage (pg. 489)

• Placental separation: usually occurs five minutes after birth, 1) a globular shaped uterus, 2) a rise of the fundus in the abdomen, 3) a sudden gush or trickle of blood, and 4) a protrusion of the umbilical cord.
• Placental delivery: Retained if not removed after thirty minutes. Shultze or Duncan.

Fourth Stage (pg. 489-490)

• 1 to 4 hours after birth
• Blood loss between 250 -500 cc
• May see increased pulse rate
• Uterus remains contracted and in the midline
• May experience a chill
• May have urinary retention

Questions?

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