Cardinal movements of labor
Ina S. Irabon, MD, FPOGS, FPSRM, FPSGE
Obstetrics and Gynecology
Reproductive Endocrinology and Infertility
Laparoscopy and Hysteroscopy
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Reference
u Cunningham FG, Leveno KJ, Bloom SL, Spong
CY, Dashe JS, Hoffman BL, Casey BM, Sheffield
JS (eds).William’s Obstetrics 24th edition; 2014;
chapter 22 Normal Labor
Cardinal movements of labor
u the cardinal movements of labor are
engagement, descent, flexion, internal
rotation, extension, external rotation,
and expulsion
u During labor, these movements not only
are sequential but also show great
temporal overlap.
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds).William’s Obstetrics 24th edition; 2014; chapter 22 Normal Labor
Engagement
u mechanism by which the biparietal diameter—
the greatest transverse diameter in an occiput
presentation—passes through the pelvic inlet
(station 0)
u the fetal head may engage during the last few
weeks of pregnancy or not until after labor
commencement.
u If the fetal head is freely movable above the
pelvic inlet, the head is sometimes referred to as
“floating.” (unengaged)
u A normal-sized head usually does not engage
with its sagittal suture directed anteroposteriorly.
Instead, the fetal head usually enters the pelvic
inlet either transversely or obliquely.
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds).William’s Obstetrics 24th edition; 2014; chapter 22 Normal Labor
Engagement
Station 0 = level of ischial spines
Engagement:
fetal position
442 Labor
DESCENT
SECTION 7
u this movement is the first requisite for birth of the
newborn.
u In nulliparas, engagement
442 may take place before the
Labor
onset of labor, and further descent may not follow until A
the onset of the second stage.
u In multiparas, descent usually begins with engagement.
SECTION 7
u Descent is brought about by one or more of four forces:
u (1) pressure of the amnionic fluid
u (2) direct pressure of the fundus upon the breech with
contractions
u (3) bearing-down efforts of maternal abdominal muscles
u (4) extension and straighteningA of the fetal body. B
C
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds).William’s Obstetrics 24th edition; 2014; chapter 22 Normal Labor
FIGURE 22-15 Mechanism of labor for the left occiput transverse
FIGURE 22-12 Synclitism and asynclitism.
FLEXION
u As soon as the descending head meets
A
resistance, whether from the cervix, pelvic walls,
or pelvic floor, it normally flexes.
u With this movement, the chin is brought into
more intimate contact with the fetal thorax, and
the appreciably shorter suboccipitobregmatic
diameter is substituted for the longer
occipitofrontal diameter C
FIGURE 22-13 Lever action produces flexion of the head. FI
Conversion from occipitofrontal to suboccipitobregmatic diameter re
typically reduces the anteroposterior diameter from nearly 12 to lin
9.5 cm. te
ad
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds).William’s Obstetrics 24th edition; 2014; chapter 22 Normal Labor th
sh
FIGURE 22-12 Synclitism and asynclitism.
Flexion
A B
A B
C D
C D
FIGURE 22-13 Lever action produces flexion of the head. FIGURE 22-14 Four degrees of head flexion. The solid line
FIGURE
Conversion from 22-13 Lever action
occipitofrontal produces flexion of the head.
to suboccipitobregmatic diameter FIGURE 22-14 Fourthe
represents degrees of head flexion.diameter,
occipitomental The solid linewhereas the broken
typically reduces the anteroposterior
Conversion from occipitofrontal diameter from nearly
to suboccipitobregmatic 12 to
diameter line connects
represents the center
the occipitomental of whereas
diameter, the anterior fontanel with the pos-
the broken
9.5 cm. typically reduces the anteroposterior diameter from nearly 12 to terior fontanel.
line connects A.the
the center of Flexion
anteriorpoor. B.with
fontanel Flexion moderate. C. Flexion
the pos-
9.5 cm. advanced. D.
terior fontanel. A. Flexion poor. B. Flexion moderate. C. Flexion complete flexion,
Flexion complete. Note that with
the chin
advanced. is oncomplete.
D. Flexion the chest.
Note The suboccipitobregmatic
that with complete flexion, diameter, the
shortest anteroposterior diameter of the fetal head, is passing
the chin is on the chest. The suboccipitobregmatic diameter, the
through the pelvic inlet.
shortest anteroposterior diameter of the fetal head, is passing
through the pelvic inlet. th
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds).William’s Obstetrics 24 edition; 2014; chapter 22 Normal Labor
Flexion: fetal
position
A
Internal Rotation C D
FIGURE 22-15 Mechanism of labor for the left occiput transverse position, lateral view. A. Engagement. B. After engagement, further
descent. C. Descent and initial internal rotation. D. Rotation and extension.
Internal Rotation into play. The first force, exerted by the uterus, acts more poste-
This movement consists of a turning of the head in such a man- riorly, and the second, supplied by the resistant pelvic floor and
the symphysis, acts more anteriorly. The resultant vector is in the
u this movement consists of turning of ner that the occiput gradually moves toward the symphysis
pubis anteriorly from its original position or, less commonly, direction of the vulvar opening, thereby causing head extension.
This brings the base of the occiput into direct contact with the
the head in such a manner that the
posteriorly toward the hollow of the sacrum (Figs. 22-15 to
22-17). Internal rotation is essential for completion of labor, inferior margin of the symphysis pubis (see Fig. 22-16).
except when the fetus is unusually small.
occiput gradually moves toward the Calkins (1939) studied more than 5000 women in labor to
ascertain the time of internal rotation. He concluded that in C
symphysis pubis anteriorly from its approximately two thirds, internal rotation is completed by the
time the head reaches the pelvic floor; in about another fourth, FIGURE 22-15 Mechanism of labor for the left occiput transverse positio
descent. C. Descent and initial internal rotation. D. Rotation and extensio
original position or, less commonly,
internal rotation is completed shortly after the head reaches the
pelvic floor; and in the remaining 5 percent, rotation does not
take place. When the head fails to turn until reaching the pelvic
posteriorly toward the hollow of the floor, it typically rotates during the next one or two contractions
in multiparas. In nulliparas, rotation usually occurs during the Internal Rotation in
sacrum next three to five contractions.
This movement consists of a turning of the head in such a man- r
t
Extension ner that the occiput gradually moves toward the symphysis
d
u Internal rotation is essential for
After internal rotation, the sharply flexed head reaches the vulva
and undergoes extension. If the sharply flexed head, on reaching
pubis anteriorly from its original position or, less commonly,
posteriorly toward the hollow of the sacrum (Figs. 22-15 to Th
completion of labor, except when
the pelvic floor, did not extend but was driven farther downward,
it would impinge on the posterior portion of the perineum and 22-17). Internal rotation is essential for completion of labor, in
would eventually be forced through the perineal tissues. When
the fetus is unusually small. the head presses on the pelvic floor, however, two forces come
except when the fetus is unusually small.
FIGURE 22-16 Mechanism of labor for left occiput anterior position.
Calkins (1939) studied more than 5000 women in labor to
ascertain the time of internal rotation. He concluded that in
approximately two thirds, internal rotation is completed by the
th
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds).William’s time the headObstetrics
reaches24theedition;
pelvic 2014;
floor;chapter
in about 22 another
Normal Labor
fourth,
Internal
rotation:
fetal
position
A B
Extension
u After internal rotation, the sharply flexed head reaches the
vulva and undergoes extension.
u When the head presses on the pelvic floor, 2 forces come
into play: 440 Labor
C D
1. first force is exerted by the uterus and acts more posteriorly
FIGURE 22-15 Mechanism of labor for the left occiput transverse position, lateral view. A. Engagement. B. After engagement, further
descent. C. Descent and initial internal rotation. D. Rotation and extension.
2. Second force is supplied by the resistant pelvic floor and the
symphysis, and acts more anteriorly.
SECTION 7
Internal Rotation into play. The first force, exerted by the uterus, acts more poste
u the resultant vector force is inThisthe direction
movement consists of aof the
turning vulvar
of the head in such a man- riorly, and the second, supplied by the resistant pelvic floor an
ner that the occiput gradually moves toward the symphysis the symphysis, acts more anteriorly. The resultant vector is in th
opening, thereby causing head extension.
pubis anteriorly from its original position or, less commonly, direction of the vulvar opening, thereby causing head extension
posteriorly toward the hollow of the sacrum (Figs. 22-15 to This brings the base of the occiput into direct contact with th
u this brings the base of the occiput into direct contact with the
22-17). Internal rotation is essential for completion of labor, inferior margin of the symphysis pubis (see Fig. 22-16).
inferior margin of the symphysis
exceptpubis
when the fetus is unusually small.
Calkins (1939) studied more than 5000 women in labor to
u Immediately after its delivery, the the
ascertain headtime of drops downward
internal rotation. He concludedso that in
approximately two thirds, internal rotation is completed by the
that the chin lies over the floating,
1. Head maternal
timebefore
the head anus.
reaches the pelvic floor; in about another fourth,5. Complete extension
engagement
internal rotation is completed shortly after the head reaches the
pelvic floor; and in the remaining 5 percent, rotation does not
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman
take place.BL, Casey
When BM, Sheffield
the head JSuntil
fails to turn (eds).William’s
reaching the Obstetrics
pelvic 24th edition; 2014; chapter 22 Normal Labor
floor, it typically rotates during the next one or two contractions
Extension:
fetal
position
7
External Rotation (Restitution)
1. Head floating, before engagement 5. Complete extension
u If the occiput was originally directed toward the left,
it rotates toward the left ischial tuberosity. If it was
originally directed toward the right, the occiput
rotates to the right.
u Restitution of the head to the oblique position is
followed by external rotation completion to the
transverse position.
u this movement corresponds to rotation of the fetal
body to bring its bisacromial diameter into relation
with the anteroposterior diameter of the pelvic
outlet.
u thus, one shoulder is anterior behind the symphysis
and the other is posterior.
2. Engagement, descent, flexion 6. Restitution (external rotation)
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds).William’s Obstetrics 24th edition; 2014; chapter 22 Normal Labor
External
rotation:
fetal
position
2. Engagement, descent, flexion 6. Restitution (external rotation)
Expulsion
u Almost immediately after external rotation,
the anterior shoulder appears under the
3. Further descent, internal rotation 7. Delivery of anterior shoulder
7
symphysis pubis, and the perineum soon
becomes distended by the posterior
shoulder.
u After delivery of the shoulders, the rest of the
body quickly passes.
4. Complete rotation, beginning extension 8. Delivery of posterior shoulder
FIGURE 22-11 Cardinal movements of labor and delivery from a left occiput anterior position.
Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds).William’s Obstetrics 24th edition; 2014; chapter 22 Normal Labor
Summary
u Cardinal Movements of Labor
1. Engagement
2. Descent
3. Flexion
4. Internal Rotation
5. Extension
6. External Rotation (Restitution)
7. Expulsion
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