Fetal head, maternal pelvis & pelvimetry

  • View

  • Download

Embed Size (px)


Fetal head & maternal bony pelvis diameters. Clinical pelvimetry.

Text of Fetal head, maternal pelvis & pelvimetry

  • Prepared by: Amaal Atta El-Seqali Rasha Khamis El-Dabbagh
  • PS IN LABOR & DELIVERY 1.Passenger= The fetus 2. Passageway= The birth canal 3. Power of labor= Force of uterine contractions 4. Placenta 5. Psyche
  • Anatomic characteristic of the fetal head & maternal pelvis
  • Objectes Fetal head Pelvic anatomy Pelvic shapes Pelvimetry Cephalopelvic disproportion
  • Fetal head Sutures Fontanelles Landmarks Diameters
  • Fetal head From an obstetrical point of view its the most important part: largest least compressible part of the fetus. most frequent presenting part
  • consists of: 1-Base: large, ossified, firmly united, and noncompressible 2-vault (cranium) consists of: -occipital bone posteriorly - 2 parietal bones bilaterally -2 frontal and temporal bones anteriorly
  • Cranial bones at birth: Thin weakly ossified easily compressible interconnected only by membranes >>> allow them to overlap under pressure & to change shape to conform to the maternal pelvis, a process known as (molding).
  • Sutures Membrane-occupied spaces between the cranial bones 1-Sagittal suture: - lies btw the parietal bones -extends in an AP direction btw the fontanelles -divides the head into right and left sides
  • 2-lambdoid suture: extends from the posterior fontanelle laterally separate the occipital from the parietal bones.
  • 3-coronal suture: extends from the anterior fontanelle laterally separate the parietal and frontal bones.
  • 4- frontal suture: lies between the frontal bones extends from the anterior fontanelle to the glabella (the prominence between the eyebrows).
  • Clinical importance of sutures molding of the head in the vertex presentation Position of fontanelle & sagittal suture can identify attitude and position of vertex. By plapating the sagittal suture during labour, degree of internal rotation & molding of the head can be noticed. In deep transverse arrest, this sagittal suture lies transversely at the level of the ischial spines.
  • Fontanelles membrane-filled spaces located at the point where the sutures intersect more useful in diagnosing the fetal head position than the sutures.
  • The anterior fontanelle (bregma) : diamond shaped area(2 3 cm) of unossified membrane formed by the junction of 4 suture. The suture are:- Anteriorly: frontal suture Posteriorly: sagittal suture Laterally: on both side:-coronal suture. It is felt on fetal head surface as a soft shallow depression. It ossifies by 18 months after birth.>>>allows the skull to accommodate the tremendous growth of the infant's brain after birth
  • Clinical importance: 1. Degree of flexion can be assessed from its position. If on vaginal examination it is felt easily, it indicates the head is not well flexed. 2. Helps in the molding of head. 3. Internal rotation of the head can be assessed from its position. 4. ICP can be roughly assessed from its condition after birth. Depression in dehydration and bulging in raised ICP. 5. CSF can be collected from its lateral angles from the lateral ventricles.
  • The posterior fontanelle: It is the triangular depressed area at the junction of 3 suture: Anteriorly: sagittal suture Posteriorly: 2 lambdoid sutures at both side. closes at 6 to 8 weeks of life Y- or T-shaped
  • Clinical importance: 1. From its relation of the maternal pelvis, position of vertex is determined. 2. Internal rotation can be assessed from its location. 3. Degree of flexion can be assessed from its position. On vaginal examination if it is felt easily and anterior fontanelle is not felt, this indicates good flexion of the fetal head.
  • landmarks front to back 1. Nasion (the root of the nose) 2. Glabella (the elevated area btw the orbital ridges) 3. Sinciput (brow) (the area btw AF & glabella)
  • 4-Anterior fontanelle (bregma) 5-Vertex (the area btw the fontanelles & bounded laterally by the parietal eminences) 6-Posterior fontanelle (lambda) 7-Occiput (the area behind & inferior to PF & lambdoid sutures)
  • Diameters 6 Anteroposterior diameters (4): presenting to the maternal pelvis depends on the degree of flexion or extension of the head Transverse diameters (2)
  • Anteroposterior diameters 1- Suboccipitobregmatic (9.5 cm): Extends from the undersurface of the occipital bone at the junction with the neck to the center of the AF.
  • Present AP diameter when the head is well flexed >>>> OT or OA position LOAROT
  • 2. Occipitofrontal (11 cm): extends from the external occipital protuberance to the glabella.
  • presenting AP diameter when the head is deflexed >>> OP
  • 3. Supraoccipitomental (13.5 cm): extends from the vertex to the chin
  • -presenting AP diameter in a brow presentation -longest AP diameter of the head
  • 4. Submentobregmatic (9.5 cm): extends from the junction of the neck and lower jaw to the center of the anterior fontanelle.
  • -presenting AP diameter in face presentations
  • Transverse diameters 1-Biparietal (9.5 cm): the largest transverse diameter extends btw the parietal bones. 2-Bitemporal (8 cm): the shortest transverse diameter extends btw the temporal bones.
  • Pelvic anatomy Bony pelvis Pelvic planes Pelvic diameters
  • The bony pelvis four bones : two hip bones(ileum, ischium & pubis) laterally & anteriorly sacrum & coccyx posteriorly 3 joints symphysis pubis anteriorly sacroiliac joints posteriorly
  • Sacrum consists of 5 rudimentary vertebrae fused together to form a single wedge-shaped bone with a forward concavity The upper border ( base) articulates with the L5 The narrow inferior border articulates with the coccyx. Laterally, the sacrum articulates with the two iliac bones The anterior and upper margins of the first sacral vertebra bulge forward sacral promontory
  • Coccyx consists of 4 vertebrae fused together to form a small triangular bone articulates at its base with the lower end of the sacrum Its vertebrae consist of bodies only, but the first vertebra possesses a rudimentary transverse process and cornua. The cornua are the remains of the pedicles and superior articular processes and project upward to articulate with the sacral cornua
  • Hip Bone In children: each hip bone consists of : the ilium, which lies superiorly the ischium, which lies posteriorly and inferiorly the pubis, which lies anteriorly and inferiorly joined by cartilage at the acetabulum At puberty, >>> fuse together to form one large, irregular bone. articulate with the sacrum at the sacroiliac joints >>>>form the anterolateral wall of the pelvis articulate with one another anteriorly at the symphysis pubis.
  • The ilium, the upper flattened part of the hip bone iliac crest runs between the anterior and posterior superior iliac spines Below these spines are the corresponding anterior and posterior inferior iliac spines The iliopectineal line runs downward and forward around the inner surface of the ilium and serves to divide the false from the true pelvis.
  • The ischium the inferior and posterior part of the hip bone ischial spine ischial tuberosity
  • 3-The pubis the anterior part of the hip bone Body bears pubic crest & pubic tubercle and articulates with the pubic bone of the opposite side at t