Bony pelvis : it is made up of four bones : the sacrum, coccyx, and two innominates (composed of the ilium, ischium,and pubis).

The false pelvis is bordered by the lumbar vertebrae posteriorly, an iliac fossa bilaterally,and the abdominal wall anteriorly. It supports the pregnant uterus. The true pelvis is a bony canal and is formed by the sacrum and the coccyx posteriorly and by the ischium and pubis laterally and anteriorly. The posterior wall is twice the length of the anterior wall. The true pelvis is area of concern because its dimensions are sometimes not adequate to permit passage of the fetus.

The pelvic inlet The plane of greatest diameter The plane of least diameter The pelvic outlet

LateralPosteriorAnteriorPelvic Planes iliopectinaeal line of the innominate bones. sacral promontory pubic crest 1- The Pelvic Inlet upper part of the obturator foramina junction of S2 & S3 posterior midpoint of the pubis 2- The Plane of greatest diameter ischial spines and sacrospinous ligaments Lower sacrum Lower edge of pubis 3- The Plane of least diameter (Mid-pelvic Plane) ischial tuberosity sacrococcygeal joint lower pubic bone 4- The Pelvic Outlet

The diameters of the pelvic planes represent the amount of space available at each level.

Pelvic inlet has five important diameters : The anteroposterior diameter : described by one of two measurements:  the true conjugate (anatomic conjugate ): from sacral promontory to superior pubis  obstetric conjugate: from sacral promontory to posterior pubis. The transverse diameter : the widest distance between iliopectineal lines Two oblique diameters :from sacroiliac joint to the opposite iliopectineal eminence The posterior sagittal diameter: from AP & transverse intersection to the middle of sacral promontory

The anteroposterior diameter : from the midpoint of the posterior surface of pubis to the junction of S2 and S3 vertebrae. The transverse diameter : widest distance between the lateral borders of the plane (upper part of obturator foramina )

The anteroposterior diameter :extends from the lower border of the pubis to the junction of S4 and S5. The transverse (bispinous ) diameter : extends between the ischial spines. The posterior sagittal diameter : from midpoint of bispinous diameter to the junction of S4 and S5

Anatomic anteroposterior diameter : from the inferior margin of pubis to tip of coccyx Obstetric anteroposterior diameter : from inferior margin of pubis to sacrococcygeal joint. Transverse diameter : between the inner surface of ischial tuberosities Posterior sagittal diameter : from middle of transverse diameter to the sacrococcygeal joint.

Android 30% Gynecoid 50% Anthropoid 18% Platypelloid 2%

Round at the inlet Side walls stright Ischeal spines of average prominence Well-rounded sacrosciatic notch Well-curved sacrum Spacious subpubic arch, with an angle of approximately 90 degrees Cylindrical shape

Triangular inlet Convergent Side walls Shallow sacral curve Long and narrow sacrosciatic notch Narrow subpubic arch It is the typical male type

Long narrow oval inlet (AP>transverse) Side walls that not converge Ischial spines close, owing to overall shape Variable, but usually posterior, inclination of the sacrum Long sacrosciatic notch Narrow, outwardly shaped subpubic arch

Oval-shaped inlet (AP<transverse) Straight or divergent side walls Ischial spines close, owing to overall shape Posterior inclination of a flat sacrum Wide bispinous diameter A wide subpubic arch flat shape

For assessment of obstetric capacity, most important measurements are: Obstetric conjugate of inlet Distance between ischial spines Subpubic angle & bituberous diameter Posterior sagittal of three planes Curve & length of sacrum - It is only an estimate - The best time is late in pregnancy when the soft tissue are distensible - It is only an estimate - The best time is late in pregnancy when the soft tissue are distensible

palpate the SACRUM It should be concave. Flat or convex is abnormal midpelvis and pelvic outlet: can’t accurately be measured clinically but it can be estimated through clinical examination.

Its purpose is to aid in determining the need for C-S. Its purpose is to aid in determining the need for C-S. Other factors affecting need for C-S include: Fetal size, Force of contractions, & Position of fetus, & degree of molding Other factors affecting need for C-S include: Fetal size, Force of contractions, & Position of fetus, & degree of molding It is an accurate measure It is an accurate measure Indications: Indications:  No longer needed in cephalic presentation  Breech delivery  To rule out pelvic abnormalities either inherited or traumatic 2 films are needed 2 films are needed  Lateral view – AP diameter  Inlet view – transverse diameter

General characteristics Sutures,Fontanelles and bones landmarks Diameters Cephalic pelvic disproportion

Fetal Head: is the Largest and least compressible part of the fetus

BaseCranium (Vault) Large, ossified, firmly united and non- compressible Consists of occipital, parietal, frontal and temporal bones At birth thin, weakly ossified, easily compressible and interconnected only by membranes Protects the vital structures within the brainstem allows molding fetal skull: 1-base 2-cranium

Definition: The membrane occupied spaces between the cranial bones.

The membrane filled spaces located at the point where the sutures intersect.

CharacteristicsClosure (ossification) Anterior Fontanelle (bregma) Diamond shape and found at the intersection of sagittal, frontal and coronal sutures 2-3 cm (larger) 18 months of life Posterior Fontanelle Y or T-shaped and found at the junction of the sagittal and lambdoid sutures 6-8 weeks of life

Nasion Glabella (bregma) (lambda) (sinciput)

1- Nasion : root of the nose 2- Glabella: elevated area between the orbital ridges 3-Sinciput(brow):the area between anterior fontanelle and glabella 4- anterior fontanelle(bregma) 5- vertex the area between the fontanelles and bonded laterally by the parietal eminence 6- posterior fontanelle ( lambda) 7- occiput the area behind and inferior to the posterior fontanelle and lambdiod sutures

Antero-posterior diameters( 4 ) Transverse diameters ( 2 )

LengthDefinitionPresentation Suboccipitobreg matic 9.5cmExtends from occipital bone at the junction of the neck to AF. When the head is well flexed as in occipitoanterior or occipitotransverse Submentobregm atic 9.5cmfrom junction of neck and lower jaw to AF. in the face presentation Occipitofrontal11cmfrom external occipital protuberance to glabella. As in occipitoposterior presentation Supraoccipitome ntal 13.5cmfrom vertex to chin. In a brow presentation ( lead to CS )

1.Biparietal(9.5cm): between the parietal bones. 2.Bitemporal(8cm): between the temporal bones

An obstetric condition where there is mismatch in size between (fetal head & the maternal pelvis), resulting in failure of the fetus to pass safely through the birth canal for mechanical reasons.

1- Absolute CPD: There is no possibility of a normal vaginal delivery (extremely rare). Fetal (Temporary): macrosomia (diabetes) & Fetal hydrocephalus Maternal (Permenant): Congenitally abnormal pelvis. Damaged pelvis (RTA). Distorted pelvis (osteomalacia).

2- Relative CPD: the baby is large but would pass through the pelvis if the mechanisms of labor function correctly. If, however, the head is deflexed or fails to rotate in the mid-cavity, then prolonged, abnormal labor will occur. CPD: Can only truly be diagnosed after a trial of labour. May be suspected antenatally in women who are ≤ 1.58m height. Should be suspected in a women with a high head at term, after excluding the other causes.

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