The height of a pregnant woman is very vital in the
elucidation of the outcome of labor. Generally,
a woman below the height of 5ft is considered to
have a small pelvis and will have difficulty in
the delivery of baby.
In the condition recognised as dystocia dystrophia syndrome,
the patient is short, very sturky and has an android (male)
type of pelvis. The patient is very likely to have difficulty in delivery.
Fundal height measurement is utilised in the determination
of the age of gestation by the method of palpation in routine
obstetrical care. The fundus rises from the false pelvis and
is palpable through the anterior wall of the abdomen at the
hypogastrium at 8-12 weeks of gestation.
At the week 16 weeks of gestation the uterine fundus has
reached midway between the umbilicus and the pubic symphysis.
At 20 weeks it has reached the umbilicus. Thereafter it increases
by about 2.5cm for every 2 weeks. It reaches midway between
the umbilicus and the xiphoid process at 28 weeks of gestation.
There are three anatomical cavities of the lesser pelvis
Diagonal conjugate diameter
In clinical assessment of the inlet dimensions, the
diagonal conjugate diameter is the single most important
measurement to be taken. It measures the diameter
from the inferior surface of the pubic symphysis to
the sacral promontory. This is best assessed by
vaginal (pelvic) examination with the use of the
index finger. The examine first of all measures his own index
finger length and determines during examination whether
he can feel for the sacral promontory or not.
The most used methods of clinical assessment of the dimensions
of the midcavity are
1. Morphology of ischial spines. The spines may be heavy or small.
If h If heavy then they should decrease the transverse diameter
ter of the midcavity and probably cause transverse arrest of
the head of the baby during labour.
2. Sacrospinous diameter is measured by insinuating two fingers
in the interval between the ischial spine and the lateral border
of of the sacrum during pelvic examination. The width of the two
examining fingers are initially noted to determine the approximate
diameter of the sacrospinous interval.
Intertubersichial diameter which measures the diameter between the
ischial tuberosities. It is best assessed with the knuckle of the examining
hand pressed firmly in the interval between the ischial tuberosities.
It should be about 8cm or above.
2. Subpubic angle is assessed by the use of the angle between
the index finger and the thumb in determining the angle between the
two inferior rami of the pubis
The following problems may be identified by the use of clinical
assessment in labor
Android pelvis is associated with outlet dystocias (difficulty
Gynecoid pelvis is the normal female pelvis but it may be
generally contracted in the gynaecoid pelvis of a small woman
which is called the justominor variety.
Anthropoid pelvis is associated with transverse arrest of the head
of the fetus in labour because of
the usual prominence of the
|Flat pelvis is always
associated with severe with severe labour
difficulty and its dimensions of the inlet are heavily contracted.
Anatomy of labour
During labour a curve is formed by the birth canal called the
curve of Carus. This curve is formed by the prolongation of
perineum below its normal position inferiorly and by the vagina
The shape of the pelvic floor forms a gutter which is directed
downwards and anteriorly. It is the bend of this gutter that is
accentuated with the formation of the Carus curve.
Once the head of the baby hits the pelvic floor the pelvic
gutter directs the head along its own configuration,
hence the rotation of head.
As the head hits the pelvic floor, internal orientation occurs and the head
rotates through an angle of 45o. This rotation brings the head into a
direct occipitoanterior position, a position it keeps till it crowns.
Further descent will cause the head to be delivered through a
movement of extension so that the occiput is delivered first.
As the shoulder enters the pelvic floor and proceeds to pass
through the same process as the head,
At the stage in which the shoulder is at oblique position
(i.e. left acromioanterior position) the head is already delivered
and it proceeds to undergo restitution by which it rotates through
an angle of 45o to the left in order to be in alignment with the orientation
of the shoulder at the pelvis.
The head then undergoes external
rotation to an occipitolateral position so that the occiput lies next
to the left thigh.
The anterior shoulder then slips under the symphysis pubis and is
delivered. This is followed by the posterior shoulder. The rest of
the baby’s body allows the delivery of the shoulders. This normal
process of labour may develop complications at any stage during
|Head crowns at perineum|
|Heads performs restitution|
|Anterior shoulder delivered|
|Posterior shoulder delivered|
Episiotomy is a procedure used to widen the vagina in
order to have an easy vaginal delivery. It is recommended in
all first deliveries (primigravids) and all cases of soft tissue
dystocias (difficult labor caused by soft tissue rigidity). A
Mediolateral, B J shaped mediolateral C Median D Schuchardt.
Episitomy incision passes through mucous membrane of vagina,
superficial transverse perineal muscle and perianal fat. The
median incision passes through the central perineal tendon. A lateral
incision is avoided because it
destroys the greater vestibular gland.
|Delivery is performed after episiotomy|
|A repair is done after delivery
The above represents the normal presentation in parturition.
Abnormal presentation may include breech delivery
in which the sacrum rather than the head is the presenting part.
© Electronic School of Medicine
Creator: Oluwole Ogunranti