Obstetrics
Topic:
Fetal Head
Management of labour
Shakeel MD. Hamza
Group 46
The skull is made up of the base of skull
and the vault or cranium.
The vault is made of occipital bone
posteriorly, the two parietals at the sides,
and the temporal bones and frontal
bones interiorly.
These bones at birth are thin, easily
compressible and joined by membrane.
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The rest of the head is composed of the firm
skull, which is made up of:
two frontal
two parietal
two temporal bones
upper portion of the occipital bone
the wings of the sphenoid.
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Sutures make molding possible and some
amount of molding is needed for vaginal
delivery.
In hydrocephalus, there is suture separation,
resulting in 'islets of bone in a sea of
membranes.'
3) Palpation of the sagital suture during
vaginal examination gives an idea of the degree
of internal rotation.
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Fontanelles are the membrane-filled spaces at the
meeting point of the sutures.
ANTERIOR FONTANELLE OR BREGMA
* Meeting point of sagittal,coronal and frontal sutures.
*Diamond shaped
*Measures 3x2 cm.
*Ossifies by one and a half years.
POSTERIOR FONTANELLE OR LAMBDA
Junction of sagittal suture and the two lambdoidal
sutures
*Smaller than the anterior fontanelle
*Y shaped
*Closes at 6-8 weeks
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POSTERIOR FONTANELLE OR LAMBDA
Junction of sagittal suture and the two
lambdoidal sutures
*Smaller than the anterior fontanelle
*Y shaped
*Closes at 6-8 weeks
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Palpation of posterior fontanelle during
vaginal examination denotes position of the
head.
Palpation of the anterior fontanelle will denote
the degree of flexion of the head.
After birth, fontanelle are useful to asses the
condition of the baby.
The fontanelles remain membranous for some
time after birth. This helps to accomodate the
marked growth of the brain.
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ANTERO-POSTERIOR DIAMETERS
1) Suboccipito-bregmatic diameter (9.4 cm) extends
from the undersurface of the occipital bone where
it meets the neck, to the centre of the anterior
fontanelle or bregma. It is the diameter that
presents when the head is well flexed and in
occipito-anterior position.
2) Occipitofrontal diameter(11 cm) extends from
the external occipital protuberance to the glabella
and presents when the head is deflexed as in
occipito-posterior.
3)Suboccipito frontal(10.5 cm) is another
presenting diameter in occipitoposterior.
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Verticomental (13.5 cm) extends from the
vertex the chin and It is the longest
antroposterior diameter of the head and the
diameter in which brow presents.
Submentobregmatic (9.4 cm) extends from the
junction of the neck and lower jaw to the centre
of the anterior fontanelle and is the diameter in
face presentation.
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The World Health Organization (WHO)
defines normal birth as follows:
The birth is spontaneous in onset and low risk
at the start of labor and remains so throughout
labor and delivery.
The infant is born spontaneously in the vertex
position between 37 and 42 weeks of
pregnancy.
After birth, mother and infant are in good
condition.
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There are 3 stages of labor.
The 1st stage—from onset of labor to full dilation
of the cervix (about 10 cm)—has 2 phases, latent
and active.
During the latent phase, irregular contractions
become progressively coordinated, discomfort is
minimal, and the cervix effaces and dilates to 4 cm.
The latent phase is difficult to time precisely, and
duration varies, averaging 8 hours in nulliparas
and 5 hours in multiparas.
Duration is considered abnormal if it lasts > 20
hours in nulliparas or > 12 hours in multiparas.
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During the active phase, the cervix becomes
fully dilated, and the presenting part descends
well into the midpelvis. On average, the active
phase lasts 5 to 7 hours in nulliparas and 2 to 4
hours in multiparas. Traditionally, the cervix
was expected to dilate about 1.2 cm/hour in
nulliparas and 1.5 cm/hour in multiparas.
However, recent data suggest that slower
progression of cervical dilation from 4 to 6 cm
may be normal. Pelvic examinations are done
every 2 to 3 hours to evaluate labor progress.
Lack of progress in dilation and descent of the
presenting part may indicate dystocia
(fetopelvic disproportion).
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The 2nd stage is the time from full cervical dilation
to delivery of the fetus. On average, it lasts 2 hours
in nulliparas and 1 hour in multiparas. For
spontaneous delivery, women must supplement
uterine contractions by expulsively bearing down.
In the 2nd stage, women should be attended
constantly, and fetal heart sounds should be
checked continuously or after every contraction.
Contractions may be monitored by palpation or
electronically.
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During the 2nd stage of labor, perineal
massage with lubricants and warm compresses
may soften and stretch the perineum and thus
reduce the rate of 3rd- and 4th-degree perineal
tears. These techniques are widely used by
midwives and birth attendants. Precautions
should be taken to reduce risk of infection with
perineal massage.
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The 3rd stage of labor begins after delivery of
the infant and ends with delivery of the
placenta. This stage usually lasts only a few
minutes but may last up to 30 minutes.