Abnormal labour Abnormal labour

Dystocia due to pelvic contractionDystocia due to pelvic contraction

Any contraction of the pelvic diameter that diminishes Any contraction of the pelvic diameter that diminishes the capacity of the pelvis can create dystocia during the capacity of the pelvis can create dystocia during labour. Pelvic contracture may be classified as follows :labour. Pelvic contracture may be classified as follows :

1 - Contraction of the pelvic inlet.1 - Contraction of the pelvic inlet.

2 - Contraction of the midpelvis.2 - Contraction of the midpelvis.

3 - Contraction of the pelvic outlet.3 - Contraction of the pelvic outlet.

4 - Generally contracted pelvis ( combination of the 4 - Generally contracted pelvis ( combination of the above ).above ).

I Contracted pelvic inlet :I Contracted pelvic inlet : Pelvic inlet usually considered contracted if its shortest Pelvic inlet usually considered contracted if its shortest

anteroposterior diameter is less than 10 cm, or if the anteroposterior diameter is less than 10 cm, or if the greatest transverse diameter is less than 12 cm. The greatest transverse diameter is less than 12 cm. The anteroposterior ( AP ) diameter i.e the obstetric anteroposterior ( AP ) diameter i.e the obstetric cojugate is usually obtained clinically by measuring the cojugate is usually obtained clinically by measuring the diagonal conjugate ( the distance between the diagonal conjugate ( the distance between the promontory of the sacrum and the lower margin of the promontory of the sacrum and the lower margin of the symphysis pubis ), and subtracting 1.5 cm from it. symphysis pubis ), and subtracting 1.5 cm from it.

Otherwise the obstetric conjugate can only be Otherwise the obstetric conjugate can only be measured by X - Ray pelvimetry, similarly the measured by X - Ray pelvimetry, similarly the transverse diameter of the inlet can only be measured transverse diameter of the inlet can only be measured by imaging pelvimetry.by imaging pelvimetry.

* * The configuration of the pelvic inlet is also an important The configuration of the pelvic inlet is also an important determinant of the adequacy of any pelvis independent determinant of the adequacy of any pelvis independent of the actual measurement of these diameters. of the actual measurement of these diameters.

* * A small woman is likely to have a small pelvis, but she is A small woman is likely to have a small pelvis, but she is also likely to have a small infant. also likely to have a small infant.

* * Normally cervical dilatation is facilitated by the Normally cervical dilatation is facilitated by the hydrostatic action of the unruptured membranes, or hydrostatic action of the unruptured membranes, or after their rupture by direct application of the after their rupture by direct application of the presenting part against the cervix. In contracted presenting part against the cervix. In contracted pelvises, when the head is arrested in the pelvic inlet, pelvises, when the head is arrested in the pelvic inlet, the entire force exerted by the uterus acts directly the entire force exerted by the uterus acts directly upon the portion of membrane that overlies the dilating upon the portion of membrane that overlies the dilating cervix., consequently early spontaneous rupture of the cervix., consequently early spontaneous rupture of the membrane is more likely to result.membrane is more likely to result.

After membrane rupture, the absence of pressure by After membrane rupture, the absence of pressure by the head against the cervix and lower uterine segment the head against the cervix and lower uterine segment predispose the less effective contraction leading to slow predispose the less effective contraction leading to slow progress or even arrest of cervical dilatation.progress or even arrest of cervical dilatation.

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* * Also in woman with contracted pelvis, face and Also in woman with contracted pelvis, face and shoulder presentation are encountered 3 times shoulder presentation are encountered 3 times more frequently, while cord prolapsed occur 4 - 6 more frequently, while cord prolapsed occur 4 - 6 times more frequentlytimes more frequently

II Contracted midpelvis :II Contracted midpelvis :

More common than inlet contraction, it is frequently a More common than inlet contraction, it is frequently a cause of transverse arrest of the fetal head in labour, cause of transverse arrest of the fetal head in labour, which can lead to difficult midforceps operation or to which can lead to difficult midforceps operation or to caesarean section.caesarean section.

The obstetrical plan of the midpelvis extend from the The obstetrical plan of the midpelvis extend from the inferior margin of the symphysis pubis, through the inferior margin of the symphysis pubis, through the ischial spines and touches the sacrum near the junction ischial spines and touches the sacrum near the junction of the fourth and fifth vertebrae. A transverse line of the fourth and fifth vertebrae. A transverse line theoretically connecting the ischial spines divides the theoretically connecting the ischial spines divides the midpelvis into anterior and posterior portions.midpelvis into anterior and posterior portions.

Average midpelvis measurement are as follows :Average midpelvis measurement are as follows :

- Transverse ( interspinous ) 10.5 cm.- Transverse ( interspinous ) 10.5 cm.

- Anteropposterior ( form the lower border of - Anteropposterior ( form the lower border of symphysis pubis to the junction of the fourth and fifth symphysis pubis to the junction of the fourth and fifth sacreal vertebrae 11.5 cm.sacreal vertebrae 11.5 cm.

- Posterior sagittal ( from the midportion of the - Posterior sagittal ( from the midportion of the interspinous line to the same point on the sacrum interspinous line to the same point on the sacrum about 5 cm.about 5 cm.

The midpelvis likely to contracted when the sum of The midpelvis likely to contracted when the sum of the interischial spinous and posterior sagittal the interischial spinous and posterior sagittal diameters of the midpelvis ( normally 10.5 + 5 = 15.5 diameters of the midpelvis ( normally 10.5 + 5 = 15.5 cm ) falls to 13.5 cm or below.cm ) falls to 13.5 cm or below.

You should suspect midpelvis contracture, whenever You should suspect midpelvis contracture, whenever the interischial spinous diameter is less than 10 cm, the interischial spinous diameter is less than 10 cm, when less than 8 cm ,it mean Contracted midpelviswhen less than 8 cm ,it mean Contracted midpelvis

No precise manual method of measuring midpelvis No precise manual method of measuring midpelvis dimensions, usually a prominent ischial spines, pelvic dimensions, usually a prominent ischial spines, pelvic sidewalls converge, or the sacroischial notch is narrow sidewalls converge, or the sacroischial notch is narrow Should arise the possibility of midpelvis contracture.Should arise the possibility of midpelvis contracture.

III Contracted pelvis outlet :III Contracted pelvis outlet :

Usually defined as decrease interischial Usually defined as decrease interischial tuberous diameter to 8 cm or less.tuberous diameter to 8 cm or less.

The pelvic outlet described as 2 triangle with The pelvic outlet described as 2 triangle with interischial tuberous diameter constituting the interischial tuberous diameter constituting the base of both.base of both.

* * Diminution in the intertuberous diameter Diminution in the intertuberous diameter with consequent narrowing of the anterior with consequent narrowing of the anterior triangle must inevitably force the fetal head triangle must inevitably force the fetal head posteriorly whether delivery can take place posteriorly whether delivery can take place partly depend on the size of the posterior partly depend on the size of the posterior triangle, or more specifically on the interischial triangle, or more specifically on the interischial tuberous diameter and the posterior sagittal tuberous diameter and the posterior sagittal diameter of the outlet.diameter of the outlet.

* * A contracted outlet may cause dystocia not so much A contracted outlet may cause dystocia not so much by itself ,but through the often associated midpelvic by itself ,but through the often associated midpelvic contracture. Outlet contraction without concomitant contracture. Outlet contraction without concomitant midpelvis contracture is rare.midpelvis contracture is rare.

* * With increasing narrowing of the pelvic arch, the With increasing narrowing of the pelvic arch, the occiput cannot emerge directly beneath the symphysis occiput cannot emerge directly beneath the symphysis pubis but is forced increasingly father down upon the pubis but is forced increasingly father down upon the ischiopubic rami. So exposing the perineum to greater ischiopubic rami. So exposing the perineum to greater danger of disruption. danger of disruption.

Pelvic fractures :Pelvic fractures : Car accident, the most common cause of pelvic Car accident, the most common cause of pelvic

fractures, when bilateral fractures of the pelvic rami fractures, when bilateral fractures of the pelvic rami occur, it will compromise the capacity of the birth occur, it will compromise the capacity of the birth canal, by callus formation or malunion. So history of canal, by callus formation or malunion. So history of pelvic fracture require careful review of previous X pelvic fracture require careful review of previous X –– Ray and MRI. Ray and MRI.

Estimation of pelvic capacity :Estimation of pelvic capacity :1 1 –– Clinical evaluation : using digital examination of the Clinical evaluation : using digital examination of the

boney pelvis during labour.boney pelvis during labour.

i.ei.e a/ a/ measure the anterior measure the anterior –– posterior diameter of the posterior diameter of the inlet ( diagonal conjugate ) by introducing 2 fingers into inlet ( diagonal conjugate ) by introducing 2 fingers into the vagina and by depressing the wrist, the tip of the the vagina and by depressing the wrist, the tip of the second finger may feel the promontory of the sacrum, second finger may feel the promontory of the sacrum, and this vaginal hand elevated until it contact the pubic and this vaginal hand elevated until it contact the pubic arch and the point on the index finger marked, the arch and the point on the index finger marked, the hand is withdrawn and distance measured between the hand is withdrawn and distance measured between the mark and the hip of the second finger and then by mark and the hip of the second finger and then by subtracting 1.5 cm, the obstetric conjugate is obtained. subtracting 1.5 cm, the obstetric conjugate is obtained.

b/ b/ Interspinous diameter of the midpelvisInterspinous diameter of the midpelvis..

c/ c/ The intertuberous distance of the pelvic The intertuberous distance of the pelvic outlet ( transverse diameter of the outlet ), here outlet ( transverse diameter of the outlet ), here a measurement of over 8 cm is normal, done by a measurement of over 8 cm is normal, done by placing a closed fist against the perineum placing a closed fist against the perineum between the ischial tuberosities after first between the ischial tuberosities after first measuring the width of the closed fist.measuring the width of the closed fist.

d/ d/ Pubic arch if narrow < 90°, can signify a Pubic arch if narrow < 90°, can signify a narrow pelvis.narrow pelvis.

similarly an unengaged head can indicate similarly an unengaged head can indicate either excessive fetal head size or reduced either excessive fetal head size or reduced pelvis inlet capacity.pelvis inlet capacity.

2 2 –– X X –– Ray pelvimetery : prognosis for succesful Ray pelvimetery : prognosis for succesful vaginal delivery in any given pregnancy cannot be vaginal delivery in any given pregnancy cannot be established on the basis of x established on the basis of x –– ray pelvimetery alone. ray pelvimetery alone. So it is of limited value in the management of labour So it is of limited value in the management of labour with cephalic presentation. But in breech vaginal with cephalic presentation. But in breech vaginal delivery, it is still used in many centers.delivery, it is still used in many centers.

3 3 –– CT CT –– scan computed tomographic scanning : the scan computed tomographic scanning : the advantage of CT pelvimetery is a reduction in advantage of CT pelvimetery is a reduction in radiation exposure. And with greater accuracy and radiation exposure. And with greater accuracy and easier perform. easier perform.

Convential x Convential x –– ray - Gonadal exposure is estimated to ray - Gonadal exposure is estimated to be 885 mrad, while CT be 885 mrad, while CT –– ray from 250 ray from 250 –– 1500 mrad. 1500 mrad.

4 4 –– Magnetic resonance imaging ( MRI ) :Magnetic resonance imaging ( MRI ) :

Advantages include :Advantages include :

a/ Lack of ionizing radiation.a/ Lack of ionizing radiation.

b/ Accurate pelvic measurement.b/ Accurate pelvic measurement.

c/ Complete fetal imaging, as well as evaluation of c/ Complete fetal imaging, as well as evaluation of soft tissue dystocia.soft tissue dystocia.

Excessive fetal size :Excessive fetal size : Selection of fetal size threshold to predict fetopelvic Selection of fetal size threshold to predict fetopelvic

and therefore, prevent obstructed labour, is not and therefore, prevent obstructed labour, is not possible because most cases of disproportion occur in possible because most cases of disproportion occur in fetus whose weight is well within the range of the fetus whose weight is well within the range of the general obstetrical population.general obstetrical population.

Also the method to estimate fetal head are also Also the method to estimate fetal head are also imprecise. The brow and suboccipital region. In a imprecise. The brow and suboccipital region. In a cephalic presentation are grasped through the cephalic presentation are grasped through the abdominal wall with the finger and firm pressure is abdominal wall with the finger and firm pressure is directed down wards in the axis of the inlet. Fundal directed down wards in the axis of the inlet. Fundal pressure by an assistance is usually helpful. The effect pressure by an assistance is usually helpful. The effect of the forces on the descent of the head can be of the forces on the descent of the head can be evaluated by concomitant vaginal examination. If no evaluated by concomitant vaginal examination. If no disproportion exist the head readily enters the pelvis disproportion exist the head readily enters the pelvis and vaginal delivery can be predicted. and vaginal delivery can be predicted.

Also the biparietal diameter and head circumference Also the biparietal diameter and head circumference can be measured by ultrasound. can be measured by ultrasound.

Maternal Maternal –– fetal effects of dystocai : fetal effects of dystocai : 1 1 –– Intrapartum infection : especially if membrane are Intrapartum infection : especially if membrane are

ruptured.ruptured.

2 2 –– Uterine rupture : especially in woman of high Uterine rupture : especially in woman of high parity and those with previous cesarean section. parity and those with previous cesarean section.

3 3 –– Pathological retraction ring : pathological Pathological retraction ring : pathological retraction ring of bandle, result from obstructed labour retraction ring of bandle, result from obstructed labour with marked stretching and thinning of the lower with marked stretching and thinning of the lower uterine segment. Sometimes seen clearly as an uterine segment. Sometimes seen clearly as an abdominal indentation and significe impending rupture abdominal indentation and significe impending rupture of the lower uterine segment .of the lower uterine segment .

4 4 –– Fistula formation : when the presenting part is Fistula formation : when the presenting part is firmly weighted into the pelvic inlet but dose not firmly weighted into the pelvic inlet but dose not advance for a considerable time, portions of birth canal advance for a considerable time, portions of birth canal lying between it and the pelvic wall may be subjected lying between it and the pelvic wall may be subjected to excessive pressure causing impaired circulation so to excessive pressure causing impaired circulation so that necrosis may occur several days late as that necrosis may occur several days late as vesicovaginal fistual, or vesicocervical or retrovaginal vesicovaginal fistual, or vesicocervical or retrovaginal fistula.fistula.

5 5 –– Pelvic floor injury : during childbirth the pelvic floor Pelvic floor injury : during childbirth the pelvic floor is exposed to direct compression form the fetal head, is exposed to direct compression form the fetal head, as well as downward pressure from maternal expulsive as well as downward pressure from maternal expulsive effort resulting in stretching and distending the pelvic effort resulting in stretching and distending the pelvic floor and this may lead to anatomical and functional floor and this may lead to anatomical and functional alteration in muscles, nerves, and connective tissue alteration in muscles, nerves, and connective tissue which may cause urinary an fecal incontinence and which may cause urinary an fecal incontinence and genital prolapsed. genital prolapsed.