Maternal pelvis..types..delivery assessment

Maternal pelvis...size.. measurement..types

1. maternal pelvis

2. Bony pelvis Two innominate bones, sacrum n coccyx Innominate bone = ilium , ischium, pubis Symphysis pubis, 2 sacroiliac joints, sacrococcygal joint Clinical importance: relax remarkably during pregnancy. At term, Increase Outlet diameter by 1.5 to 2 cm. False pelvis : above linea terminalis/ pelvic brim, support enlarged uterus during pregnancy True pelvis : below linea terminalis Ant wall 5cm, post wall 10cm 3 parts- inlet/brim, cavity, outlet

3. Planes and diameters 4 imaginary planes Plane of pelvic inlet Plane of greatest pelvic dimensions (no sig) Plane of Least pelvic dimensions – significant Plane of outlet Importance of ischial spines: Diameter is smallest Deep transverse arrest occurs Represent zero station Internal rotation occurs here Landmark for pudendal block When engagement occurs, vertex is at this level Forward axis of pelvic curve begins here

4. Pelvic inlet Inlet is ovoid Post: promontory, alae sacrum Lat: linea terminalis ( sacroiliac articulation, iliopectineal line, iliopubic eminence, pectineal line, pubic tubercle and pubic crest)  Ant: symphysis pubis Ap diameters: True conjugate: 11 cm, superior surface of sp to middle of sacral promontory. No significance Diagonal conjugate: 12.5 cm, subpubic angle to middle of sacral promontory . Measured clinically. The inlet is adequate if dc 12cm or more Obs conjugate: 10.5 cm , shortest, the prominent bony projection on the inner surface of sp to middle of sacral promontory. Most important Obs conjugate calculated by sub 1.5-2 cm from diagonal conjugate.

5. Transverse diameter: Widest of inlet, 13.5cm, distance b/w the 2 farthest points over the iliopectineal lines, most fetus engage in transverse or oblique diameter Oblique diameter: 12.5 cm , from sacroiliac joint to opp iliopubic Eminence Post sagittal diameter: 5cm, from point of intersection of obstetric conjugate n transverse diameter to midpoint of sacral promontory Sacrocotyloid : 9.5 cm, distance btw midpoint of sacral promontory and ipsilateral iliopubic Eminence.

6. Midpelvis Most important plane of pelvis. Bounded by 4 th and 5 th sacral vertebrae, ischial spines, lower border of pubic symphysis. Cannot be measured clinically conTraction suspected when: prominent ischial spines Sacrosciatic notch less than 2 Fingerbreaths wide Sacrum flat, converging side walls . Subpubic arch is narrow AP dia : 11.5cm, From junction of 4 th n 5 th sacral vertebrae to lower border of pubic symphysis Transverse dia : 10cm or slightly greater, between ischial spines Posterior sagittal dia : 6cm, from inter spinous diameter to junction of 4 th n 5 th sv

7. Anatomic Pelvic outlet Made up of two triangles with common base through 2 ischial tuberosities. Anterior triangle : subpubic angle as Apex, pubic Rami n ischial tuberosities as sides Posterior triangle : sacrococcygeal joint as Apex, sacrotUberous ligaments as sides AP diameter: 12cm, lower margin of pubic symphysis to sacrococcygeal jn Transverse diameter: 10.5 cm, distance between inner edges of ischial tuberosities. Placing a fist on perineum Posterior sagittal diameter: 7cm, from the middle of transverse diameter to sacrococcygeal jn

8. Other definitions Subpubic angle: meeting of two descending pubic Rami. 85-90° Waste space of morris : distance between ps and fetal head under subpubic arch. Nly , less than 1cm. If more than 1cm, AP diameter is reduced. Inclination of pelvis: assessed in standing position. Plane of inlet Makes 60° with horizontal. high inclination lead to delay in engagement Axis of birth canal: joining axis of inlet , cavity and outlet. Curve with convexity fitting sacral curvature, called anatomical pelvic axis or “curve of Carus ” Obs axis: course taken by presenting part as it moves down the pelvis. First down n backwards upto ischial spines Then down n forwards

9. Classification of pelvis Caldwell and moloy classification 4 types Gynaecoid : normal female pelvis, in majority. Round or transverse oval. Both ant n post segments are roomy. Sacrum well curved, parallel side walls, spine not prominent, wide sacrosciatic notch and subpubic angle 90°. Fetal head engages in transverse or oblique diameter, normal delivery occurs. Anthropoid : ape like pelvis. Anteroposteriorly oval . Posterior segment roomy. Head engages in AP diameter. Delivery occurs as face to pubis or occipito -posterior because non rotation is common here.

10. Android : male type, inlet is wedge, Cavity funnel shaped. All diameters are reduced. Sacrum is flat, side walls converging, prominent ischial spines, narrow sacrosciatic notch, subpubic angle less than 90°. Head engagement is difficult, deep transverse arrest, op position, prolonged & obstructed labor common. Difficult instrumental deliveries Platypelloid : flat pelvis, inlet is transverse oval. Capacity is reduced. At outlet, subpubic angle is wide. Head engages in transverse diameter with marked asynclitism. Delay in inlet , caesarean in many people. If the head is able to negotiate inlet by asynclitism, usually no problem. But internal rotation will occur only when head is low down in pelvis, late in labor.

11. Clinical pelvimetry

12. steps 1. Start with the sacral promontory and then follow the curve of sacrum downwards alongs midline a. In an adequate pelvis , the promontory not be easily palpated , the sacrum is curved, and the coccyx cannot be felt. b. In an inadequate pelvis , the sacral promontory is easily palpated and prominent, sacrum is straight, and the coccyx is prominent 2. After assessing the sacrum, the fingers are the moved laterally, to feel the sacrospinous ligaments, later the ischial spines can be palpated. Then interspinous distance is estimated by separating the index and middle fingers wide apart a. In an adequate pelvis, at least two fingers be placed over the sacrospinous ligament (assessment of sacrosciatic notch) and the ischial spines are not prominent. b. In an inadequate pelvis, the sacrospinous ligaments usually allow less than two fingers and the ischial spines may be sharp and prominent .

13. 3. Next, the retropubic area ( forepelvis ) is palpated by placing two fingers behind the symphysis pubis with the palm of the hand facing forwards. fingers are then moved laterally to both sides a In an adequate pelvis, the retropubic area is flat . b. In an inadequate pelvis, the retropubic area is angulated. 4. To measure the subpubic angle , the examining fingers are turned so that the palm of the hand faces upwards and the angle under the pubis is felt. a In an adequate pelvis, three fingers can be placed under the pubis and the subpubic angle is about 90° b. In an inadequate pelvis, only two fingers can be placed under the pubis and the subpubic angle is about 60° .

14. 5. The hand is then withdrawn from the vaginal introitus and the intertuberous diameter is assessed with the knuckles of the closed fist of the hand placed between the ischial tuberosities. a In an adequate pelvis, the intertuberous diameter allows four knuckles . b. In an inadequate pelvis, the intertuberous diameter allows less than four knuckles.

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