PREGNANCY AND LABOR AT FETAL MALPRESENTATIONS AND ABNORMAL PELVIS
Planes and Diameters of the Normal Pelvis
The pelvis has four imaginary planes:
1– plane of the pelvic inlet,
2 – plane of greatest pelvic dimensions,
3 – the plane of the midpelvis (least pelvic dimensions),
4 – the plane of the pelvic outlet.
Pelvic inlet is bounded posteriorly by the promontory, laterally by the linea terminalis, and anteriorly by the horizontal rami of the pubic bones and symphysis pubis. Four diameters of pelvic inlet are described: the anterposterior (11cm), the transverse (13cm), and two obliques (12 cm from left or right sacroiliac synchondroses to the iliopectineal eminence on the opposite side of the pelvis).
The plane of greatest pelvic dimension extends from the middle of the posterior surface of the symphysis pubis through the ischial bones over the middle of the acetabulum to the junction of second and third sacral vertebrae. Its anteroposterior and transverse diameters are 12,5 cm.
The midpelvis at the level of the ischial spines is particular importance following engagement of the fetus head in obstructed labor. The transverse diameter (interspinous) is 10,5 cm and anteroposterior is 11cm.
Pelvic outlet has two diameters: anteroposterior extends from the lower margin of the symphysis pubis to the tip of the coccys (9,5cm) and transverse diameter between the inner edges of the ischial tuberosities 11,5 cm.
The main external pelvic sizes:
D. Spinarun - distance between anterior superior iliac spines from both sides. It has 25-26 cm.
D. Cristarum – distance between iliac crista from both sides. It is 28-29 cm.
D. Trochanterica – distance between trochanter majors from both sides. It has 31-32 cm.
C. Externa - distance between midpoint of superior surface of the symphysis pubis and suprasacralis fossa.
Michael’s’ rhomb. It has 4 angles. The upper angle is located in the suprasacralis fossa. The lower angle is situated in the apex of coccyx, and laterally angles are situated in the posterior superior iliac spines. In the women with normal pelvis rhomb has regular form. It vertical diameter has 11 cm, and horizontal diameter is 10 cm.
Solovjov’ index. It is estimated by the circumference of radiocarpal joint. It has 14-16 cm and indicates into bones’ pelvic thickness.
The additional external pelvic sizes:
Lateral conjugate –is a distance between the anterior superior iliac spine and posterior superior iliac spine of the same iliac bone. It has 14.5-16 cm.
Oblique conjugate –is a distance between the right anterior superior iliac spine to the left posterior superior iliac spine. It has 14.5-16 cm.
Anteroposterior diameter of the pelvic outlet is a distance between the lower par4t of symphysis pubis and apex of the coccyx. It has 9.5 cm.
Transverse diameter of the pelvic outlet is a distance between the posterior portions of the ishial tuberosities. It has 11.5 cm.
The main internal pelvic sizes:
The widest anteroposterior diameter of the pelvic inlet is called obstetric conjugate. It runs from the upper midpoint of the symphysis to the promontorium. It has 11 cm. It is one of the most important pelvic dimension.
Indirect ways of true conjugate estimation:
1. An estimate of the obstetric conjugate is made by determining of the diagonal conjugate. During a vaginal examination, the physician attempts to reach the sacral promontory with the middle finger of the examining hand. The index finger of the free hand marks the point where the lower border of the pubic syphysis impinges on the examining hand proximal to the metacarpophalangeal joint of the index finger. This measurement, the diagonal conjugate, usually exceeds the obstetric conjugate by 1.5 to 2 cm.
2. External conjugate exceeds the obstetric conjugate by 9 cm.
3. Vertical dimension of Michael’s’ rhomb equal obstetric conjugate.
CONTRACTED PELVIS
Anatomically contracted pelvis is characterized by shortening of all or one diameters of the true pelvis into 1,5 - 2 cm and more.
Clinically or functional contracted pelvis is usually defined as pelvis with normal dimensions, but vaginally delivery is impossible due to “fetopelvic disproportion”.
The main causes of “cephalopelvic disproportion” are fetal macrosomia, postdate pregnancy, uterine inertia, fetal malpresentation, especially fetal head extension – sinciput vertex, brow, face anterior position.
Clinic signs of clinically contracted pelvis:
1. Head is arrested in the pelvic inlet (absence of fetal descending in complete cervical dilation and adequate uterine contractions).
2. Uterine contractions abnormality.
3. Positive Vasten’ sign (if disproportion between fetal head and symphisis pubis is prominent - Vasten’ sign is positive, if disproportion between fetal head and symphisis pubis is absent - Vasten’ sign is negative).
4. Signs of urinary bladder compression.
5. Edema of the cervix, and vaginal walls, productions of fistulas.
When the presenting part is firmly wedged into the pelvic inlet but does not advance for a considerable time, portions of the birth canal lying between it and the pelvic wall may be subjected to excessive pressure. As a circulation is impaired, the resulting necrosis may become manifest several days after delivery by the appearance of vesicovaginal, vesicocervical, or rectovaginal fistulas.
6. Danger of uterine rupture.
When the disproportion between the head and the pelvis is so pronounced that engagement and descent do not occur, the lower uterine segment becomes increasingly stretched, and the danger of its rupture becomes imminent. In such cases,. a pathologic contractile ring may develop and can be felt as a transverse or oblique ridge extending across the uterus somewhere between the symphysis and the umbilicus. Whenever this condition is noted, prompt cesarean delivery must be employed to terminate labor and prevent rupture of the uterus.
7. Pushing occurs if fetal head is situated in the plane of inlet.
Management in the case of clinically contracted pelvis – only cesarean section.
Pelvic classification according to form of contractions:
1. Often occurred
· generally contracted pelvis;
· flat pelvis: simple flat pelvis, flat rachitic pelvis, generally contracted flat pelvis.
Generally contracted pelvis is characterized by diminution of all true pelvic diameters (anteroposterior, transverse, and oblique) into 1-2 cm. Subpubic arch is narrow. Average sizes of the pelvis are: D. spinarum – 23cm, D. cristarum – 26 cm. D. trochanterica - 29 cm, C. externa – 18 cm, C. diagonalis – 11 cm, C. vera – 9 cm.
Course of labor:
· prolongation of labor;
· considerable fetal head flexion thanks to which it is elongated in the ocipitofrontal diameter (dolichocepaly);
· posterior fontanel is situated into the axis of pelvis;
· considerable molding of the fetal head. Caput succedaneum is formed in the area of posterior fontanel;
· with increasing narrowing of the pubic arch, the occiput cannot emerge directly beneath the symphysis pubis but is forced increasingly farther down upon the ishiopubic rami. It may play an important part in the production of perineal tears.
Management of labor. Vaginally delivery is possible.
Flat pelvis - is usually defined as diminution of anteroposterior diameters of true pelvis, transverse and oblique diameters are normal.
Simple flat pelvis is defined as shortening of anteroposterior diameters at all levels of true pelvis, as a result of this sacrum is inclined anteriorly to pubis.
Average sizes of the pelvis are: D. spinarum – 26cm, D. cristarum – 29 cm. D. trochanterica - 31 cm, C. externa – 18 cm, C. diagonalis – 11 cm, C. vera – 9 cm.
Course of labor:
· prolongation of labor;
· sagittal suture of the fetal head arresting in the transverse diameter of the plane of inlet;
· fetal head extension until bitemporal fetal head diameter would be situated in the anteroposterior diameter of the plane of inlet;
· anterior fontanel is the leading point of the fetal head (lowermost situated);
· asynclitism should be presented (anterior or posterior);
· considerable molding of the fetal head. Caput succedaneum is formed in the area of anterior fontanel.
Management of labor. In the case of posterior asynclitism vaginal delivery is impossible thanks to engagement of posterior shoulder into the plane of inlet. Cesarean section should be performed.
Flat rachitic pelvis – is characterized by some peculiarities:
1. True conjugate is shortened.
2. Sidewalls tend to converge, as result of this D. spinarum and D. cristarum are equal.
3. Additional promontorium may be presented between 1 and 2 vertebrae of sacrum
4. Subpubic arch is shallow and wide
5. Top of the sacrum is situated posteriorly that’s why dimensions of the pelvic outlet are normal or even increased.
Average sizes of the pelvis are: D. spinarum – 26cm, D. cristarum – 26 cm., D. trochanterica - 31 cm, C. externa – 17 cm, C. diagonalis – 10 cm, C. vera – 8 cm.
Course of labor is the same as in the simple flat pelvis. But thanks to normal or even increased anteroposterior size of pelvic outlet perineal tears as result of quick second stage labor may be presented.
Management of labor. Vaginal delivery is possible.
Generally contracted flat pelvis is characterized by combination of the signs of generally contracted and flat pelvis.
Average sizes of the pelvis are: D. spinarum – 24cm, D. cristarum – 25 cm., D. trochanterica - 28 cm, C. externa – 16 cm, C. diagonalis – 9 cm, C. vera – 7 cm.
Course of labor depends from predominance of kind of pelvis contraction.
Management of labor. Cesarean section is the method of choice.
2. Rare occurred contracted pelvis: obliquely contracted pelvis, obliquely dislocated pelvis, transverse contracted pelvis, osteomalacic pelvis, funnel-shaped pelvis, spondylolisthetic pelvis, contracted pelvis as a result of exostosis and bone tumors. Management of labor. Cesarean section should be performed in all of these types of pelvis.
Pelvic classification according to degree of contraction:
Four degrees of pelvic contractions should be distinguished:
I degree – True conjugate is 11-9 cm. Vaginal delivery is possible.
II degree – True conjugate is 9-7,5 cm. Vaginal delivery is possible.
III degree – True conjugate is 7,5 – 5,5 cm Cesarean section is performed.
IV – degree – True conjugate is 5.5 cm. Cesarean section is performed.
BREECH PRESENTATIONS
There is a fundamental difference between delivery in cephalic and breech presentation. With a cephalic presentation, once the head is delivered, typically the rest of the body follows without difficulty. With a breech, however, successively larger or, in case of the head, very much less compressible parts of the fetus are born.
Spontaneous complete expulsion of the fetus that presents as a breech, as described below, is seldom successfully accomplished. As the rule, either cesarean section of vaginal delivery that requires skilled participation by the obstetrician is essential for a favorable outcome.
Etiology. Breeches are much more common at the end of the second trimester of pregnancy than at or near term. Factors other than prematurity that arrear to predispose to breech presentation include uterine relaxation association with great parity, multiple fetuses, hydramnion, hydrocephalus, anencephalus, previous breech delivery, uterine anomalies, and tumors.
Classification. The varying relations between the lower extremities and buttocks of the fetus in breech presentation form the categories of frank breech, complete breech, incomplete breech presentation, footling and kneeling presentation.
In frank breech presentation the lower extremities are flexed at the hips and extended at the knees and thus the feet lie in close proximity to the head.
In complete breech presentation the lower extremities are flexed at the hips and at the knees.
In incomplete breech presentation the lower extremities are flexed at the hips and at the knees and the one or both feet lie below the breech.
In footling presentation the feet lies lower than breech.
The kneeling presentation is the especial form of the breech, when the fetal knees are lower than the breech.
Diagnosis. The diagnosis of the breech presentation may be making with the help of external and internal obstetrics investigation. With the first maneuver of the external examination we identify the hard, round, ballottable fetal head to occupy he fundus of the uterus. The second maneuver indicates the back to be on one side of the abdomen and the small parts in other. On the third maneuver the breech is movable above the pelvic inlet. The heart sounds of the fetus are usually heard loudest slightly above the umbilicus.
Vaginal examination. In frank breech presentation only buttocks and its characteristics components (both ischial tuberosities, the sacrum, the anus, the external genitalia) are usually palpable. In incomplete breech presentation the buttocks and the feet may be palpated. In footling the fetal feet are lower than buttocks.
Biomechanism of labor in breech presentation.
I moment – the internal breech rotation. The breech rotates and the fetal intertrochanteric diameter from one of oblique size of the pelvic inlet to anteteroposterior size of the pelvic outlet.
II moment – the lateral flexion of the body. The anterior hip is stemmed against the pubic arc. By lateral flexion of the fetal body the posterior hip is forced over the anterior margin of the perineum. Then anterior hip is born.
III moment – the internal shoulders rotation. After the birth of the breech, there is the slight external rotation as a result of the descends and rotations of the shoulders. The shoulders rotates on the pelvic floor and diameter biacromialis occupies anteroposterior diameter of the pelvic outlet.
IV moment – the lateral flexion the body in the thoraco-brachial part. The shoulders are born.
V moment – the internal rotation of the head. The rotation begins when the fetal head descends from the plane of greatest pelvic dimensions to the least pelvic dimensions (midpelvis). The rotation is complete when the head reaches the pelvic floor, the sagittal suture is in the anteroposterior diameter of the pelvic outlet and the small fontanel is under the symphysis.
VI moment – the flexion of the fetal head. The head fixes with its fossa suboccipitalis to the inferior margin of symphysis pubis and flexes. The face, forehead, vertex, and occiput are born.
The manual aids in breech presentations.
The manual aid by Tsovyanov I in frank breech presentations.
The aim of the manual aid: to prepare the maternal ways to the delivery of the head and shoulders and to keep the normal attitude of the fetus.
In the frank breech presentation the fetus extremities are flexed at the hips and extended at the knees and thus the feet lie in close proximity to the head. The circumference of the thorax with the crossing on it arms and legs is larger than circumference of the head and the after-coming head deliveries easily.
The technique. The aid begins after the delivery of the buttocks. The obstetrician’s hands are applied over the buttocks, the thumbs placed on the fetus sacrum and other fingers on the legs. The doctor gently supports the legs to avoid its flexion. If the normal attitude of the fetus is keeping the head deliveries easy.
The classic manual aid on the labor in complete and incomplete breech presentation.
The aim of the classic manual aid: to help of the shoulders and the head delivery.
The classic manual aid begins when the lower angular of the anterior scapula became visible. There are 4 moments of the classic manual aid.
I moment – the delivery of the posterior arm. The posterior shoulder must be delivered first. The feet are grasped in one hand and drawn upward over the groin of the mother toward which the ventral surface of the fetus is directed; in this manner, leverage is exerted upon the posterior shoulder, which slides out over the perineal margin, usually followed by the arm and hand.
II and III moment – the external trunk rotation and the freeing the posterior arm. The aim of this moment is the reverse of the anterior shoulder to the sacrum and the delivery of second arm. The obstetrician applies his hand on the lateral sides of the fetus trunk and rotates it. The direction of the movement must be in this way: the occiput must go under the symphysis pubis. When the posterior shoulder and arm appears at the vulva the doctor put two fingers into the vagina, the fingers passed along the humorous until the elbow is reached. The fingers are now used to splint the arm, which is swept downward and delivered through the vulva.
IV moment – the freeing of the head. After the shoulder are born, the head usually occupies an oblique diameter of the pelvic with the occiput directed anteriorly. The fetal head may then be extracted by the method of Mauriceau-Levret. Employing the Mauriceau-Levre maneuver to help flex the head, the doctor’s middle finger of one hand are applied into the fetal mouth, while the fetal body rests upon the palm of the hand and fore arm, which is straddled the fetal legs. Two fingers of the operator’s other hand are then hooked over the fetal neck and grasping the shoulders, downward traction is applied until the suboccipital region appears under the symphysis. The body of the fetus is then elevated toward the mother abdomen, and the mouth, nose, brow and the occiput emerge over the perineum. Gentle traction should be exerted by the fingers over the shoulders.
The manual aid by Tsovyanov II in footling presentations.
The aim of the manual aid: To perform the footling presentation to the incomplete breech and to prepare the maternal ways to the delivery of the head and shoulders.
The doctor covers the area of the vulva with the sterile napkin and puts up resistance to the delivery of the feet. The feet are flexing and the footling presentation becomes incomplete breech presentation. Than the delivery manage as in incomplete breech presentation.
The management of the breech delivery.
1. To try the minimize infant mortality and morbidity, cesarean section is preferred.
Favorable factors for breech delivery – multiple pregnancy, second fetus is in breech.
Indications for breech extraction:
· The requirement for instant vaginal delivery;
· Cases in which one is already committed to vaginal delivery and cesarean section is not appropriate or feasible (maternal indications – preeclampsia, hard heart and pulmonal diseases, cord prolapse; fetus indications – acute hypoxia);
· The breech extraction is committed after the operation.
The conditions for breech extraction:
· The cervix must be completely dilated and retracted high in the pelvis (although the breech – especially in footling presentation – may pass the cervix without incident, the shoulders or head will surely be trapped by incompletely dilated cervix);
· The uterus must be relaxed;
· The normal fetopelvic proportion;
· The rupture of membranes.
The techniques for breech extraction.
The techniques for the operation of extraction fetus on the two legs.
During total breech extraction, the obstetrician’s entire hand should be introduced through the vagina and both feet of the fetus grasped. The ankles are held with the second finger lying between them. The feet are then brought down the vagina, and gentle traction applied until they appear at the vulva. Now both feet are grasped and pulled through the vulva. As the legs commence to emerge through the vulva, they should be wrapped in a sterile towel to obtain a firmer grasp, for the vernix caseosa renders them slippery and difficult to hold. Downward gentle traction is then continued.
As the legs emerge, successively higher portion are grasped, first the calves and later the thighs. When the breech appears at the vulva, gentle traction is applied until the hips are delivered. As the buttocks emerge, the back of the infant usually rotates to the anterior. The thumbs of the operator are then placed over the sacrum and gentle downward traction is continued until the costal margins, and then, the scapulas become visible. The back of the infant tends to turn spontaneously toward the side of the mother to which it originally directed. If turning does not occur, slight rotation should be added to the traction, with the object of bringing the bisacromial diameter of the fetus in the antero-posterior diameter of the pelvic outlet.
There are two methods of delivery of the shoulders: with the scapulas visible, the trunk is rotated in such a way that the anterior shoulder and the arm appear at the vulva and can easily be released and delivered first. The operator is shown rotating the trunk of the fetus counterclockwise to deliver the right shoulder and arm. The body of the fetus is then rotated in the reverse direction to deliver the other shoulder and arm. If trunk rotation is unsuccessful, the posterior shoulder must be delivered first. The feet are grasped in one hand and drawn upward over the groin of the mother toward which the ventral surface of the fetus is directed; in this manner, leverage is exerted upon the posterior shoulder, which slides out over the perineal margin, usually followed by the arm and hand. Then, by depressing the body of the fetus, the anterior shoulders emerges beneath the pubic arch, and the arm and hand usually follow spontaneously. Thereafter, the back tends to rotate spontaneously in the direction of the mother’s symphysis. If upward rotation fails to occur, it is effected by manual rotation of the body.
Delivery of the head may then be accomplished.
After the shoulders are born, the head usually occupies an oblique diameter of the pelvis with the chin directed posteriorly. The fetal head may then be extracted either with forceps, which is the method preferred by many obstetricians, or by so-called Mauriceau maneuver.
Employing the Mauriceau maneuver to help flex the head, the operator’s index and middle finger of the hand are applied over the maxilla, while the fetal body rests upon the palm of the hand and forearm, which is straddled by the fetal legs. Two fingers of the operator’s other hand are then hooked over the fetal neck, and grasping the shoulders, downward traction is applied until the suboccipital region appears under the symphysis. The body of the fetus is then elevated toward the mother’s abdomen, and the mouth, nose, brow and eventually the occiput emerge successively over the perineum. Gentle traction should be exerted by the fingers over the shoulders. At the same time, suprapubic pressure, appropriately applied by an assistant.
The transverse lie is the condition when the long axis of the fetus is approximately perpendicular to that of the uterus. When it forms an acute angle, an oblique lie results. An oblique lie is usually only transitory, however, for either a longitudinal or transverse lie commonly results when labor supervenes. For this reason, the oblique lie is termed unstable lie.
An unstable lie is one in which the presenting part alters from week to week. It may be either a transverse or oblique lie or possibly a breech presentation. These are relatively uncommon events but are found in association with the following conditions:
1. Grand multipara. This is by far the commonest factor, due to the lax uterine and abdominal walls, which prevent the splinting effect found in women with lesser parity.
2. Polyhydramnios. The volume of fluid distends the uterus and allows the fetus to swim like a goldfish in a bowl — often taking up an oblique or transverse lie.
3. Prematurity. Here there is a relative excess of fluid to the fetus. If preterm labour occurs, the fetus may be found to have a transverse lie.
4. Subseptate uterus. The septum prevents the fetus from turning in utero.
5. Pelvic tumors such as fibroids and ovarian cysts may not only prevent the lower pole from engaging, but cause it to take up a transverse lie.
6. Placenta praevia. This usually prevents engagement of the presenting part. Because of this it may present with the fetus in an oblique or transverse lie.
7. Multiple pregnancies may present with a transverse lie. If this does occur, it is more common in the second twin.
Diagnosis of the transverse and oblique lies:
1. The external inspection shows than the abdomen is unusually wide from side to side, whereas the fundus of the uterus extends scarcely above the umbilicus.
2. On palpation, with the first maneuver no fetal pole is detected in the fundus.
3. On the second maneuver, a ballottable head is found in one side of uterus and the breech in other.
4. The third and fourth maneuvers are negative unless labor is well advanced and the shoulder has become impacted in the pelvis.
5. When the fetal head is situated in the left side of the uterus the first position of the fetus is identified. When the fetal head is situated in the right side of the uterus the second position is recognized.
6. On vaginal examination, in the early stages of labor, the side of the thorax, if it can be reached, may be recognized above the pelvic inlet. When the dilatation is further advanced, the scapula and the clavicle are distinguished on opposite sides of the thorax. Later in the labor, the shoulder becomes tightly wedged in the pelvic canal, and a hand and arm frequently prolapse into the vagina and through the vulva.
Management of transverse and oblique lie. It is not uncommon for the fetus to have a transverse lie until about the 32nd week of pregnancy. If the transverse lie persists after this time a cause should be determined. An ultrasound examination should be done to exclude placenta praevia, ovarian tumor or fibroid and if either of these conditions are present an elective cesarean section should be performed at 38-39 weeks of gestation. The ultrasound is also used for identifying twins and a subseptate uterus, whilst a vaginal examination will confirm a pelvic tumor.
The main risk of a transverse or oblique lie is in association with preterm rupture of the membranes and cord prolapse. When diagnosed the state of the cervix should be checked. If the cervix is dilated, the patient should be admitted to hospital. If, however, the cervix is closed and the membranes are intact the patient may be reviewed on a regular basis. If no easily identifiable cause is found, attempted external cephalic version can be made after 34 weeks. In grand multipara patients, the fetus will usually turn easily but will often swing back to an abnormal lie. If the abnormal lie persists or constantly reoccurs, the woman should be admitted to hospital by the 38th week. If external version is successful at this stage and the patient's cervix is favorable then artificial rupture of the membrane can be performed with the head held over the pelvic brim and an oxytocin drip commenced to augment uterine activity. If the cephalic presentation is maintained, labor may be allowed to continue.
Management of transverse or oblique in labor - cesarean section must be performed.
Complications of a transverse lie. If a mother goes into labor with a transverse or oblique lie, several catastrophes may occur. Because this occurs more commonly in multiparous women and their uterine activity is often much stronger, rupture of the uterus is more likely. When the membranes rupture there is a greatly increased danger of cord prolapse, prolapse of the arm- persistent transverse lie occur. If the fetus is alive – cesarean section immediately, if die – fetal destroying operation.
OBSTETRICS VERSIONS
Operations for correction of abnormal lie or presentation of fetus definite as obstetrics versions. There are two types of obstetrics versions: external and internal podalic version.
Indications for obstetrics versions: fetal malpresentations (breech, transverse and oblique lie).
Contraindications. Complicated pregnancy, multifetal pregnancy, congenital uterine anomalies, placenta previa, feto-pelvic disproportion.
Conditions: for the external version – 32-36 weeks, intact membranes, normal movement of the fetus in the uterus, satisfactory fetal and mother condition; for the internal podalic version – cervix must be fully dilated, intact or just rupture membranes, normal movement of the fetus in the uterus, satisfactory mother condition, absence of fetopelvic disproportion.
The internal podalic version consists of such moments:
1. Inserting a hand into uterine cavity.
2. Finding a foot.
3. Grasping one foot.
4. Drawing foot through the cervix while exerting pressure transabdominally in the opposite direction on the upper portion of the body.
The version is finished when fossa poplitea of the grasping foot in presented in the pudendal cleft.
DEFLEXED PRESENTATIONS
There are 3 types of fetal head extension – sinciput vertex, brow and face presentation.
Etiology. The causes of deflexed presentation are manifold, there are the factors that favors extension or prevents flexion the head. Extended position of the head occur more frequently when the pelvis is contracted or fetus is very large. In multiparous women the pendulous abdomen predisposes to deflexed presentation. In exceptional instances, marked tumors of the fetal neck or coils of cord about the neck may cause extension. Anencephalic fetus present by the brow or face because of faulty development of the cranium.
Sinciput vertex presentation - is a I degree of head extension.
Diagnosis. The diagnosis of the deflexed vertex presentation bases on the results of the vaginal palpation: the sagittal suture, the large and the small fontanels on the same level. The fetal head presents with a fronto-occipital diameter, a leader point is the large fontanel.
The cardinal movements of labor in deflexed vertex presentation are:
· deflexion;
· internal rotation;
· flexion;
· extension;
· internal rotation of the fetal body and external rotation of the fetal head.
1. Deflexion. The sagittal suture is in the transverse or oblique size of the pelvic inlet. The head fixes to the inlet and some deflexed. The large fontanel becomes the leader point.
2. Internal rotation. This movement is a manner that the occiput gradually moves from its original position posteriorly towards the sacrum os. The rotation is complete when the head reaches the pelvic floor; the sagittal suture is in the anteroposterior diameter.
3. Flexion of the head. Flexion begins when the head fixes by its root of the nose (the first fixing point) to the inferior margin of symphysis pubis. The flexion finishes when the occiput comes to the tip of sacrum and the second fixing point forms.
4. Extension of the head. After internal rotation and flexion the fetal head closely touched with the area of the occiput to the tip of the sacrum. The head extends and deliveries.
5. Internal rotation of the fetal trunk and external rotation of the fetal head. This moment realizes as in anterior occiput presentation.
The brow presentation is a II degree of extension.
With the brow presentation, that portion of the fetal head between the orbital ridge and the frontal suture presents at the pelvic inlet. The fetal head thus occupies a position midway between full flexion (ociput) and full extension (mentum or face). Except when the fetal head is very small or the pelvis is unusually large, engagement of the fetal head and subsequent delivery cannot take place as long as the brow presentation persists.
Diagnosis. The diagnosis of the brow presentation bases on the results of the external obstetrics examination and vaginal palpation. The brow presentation may be recognized by abdominal palpation when both the occiput and chin can be easily palpated. The reliable information can be felt by the vaginal examination: the frontal suture, the large fontanel, orbital ridges, eyes, and root of the nose. The nose and mouth can not be palpable.
The fetal head presents with a mento-occipital diameter, a leader point is the middle of the frontal suture.
The delivery at term in brow presentation is impossible. The preterm delivery, when the fetus is small is possible and the characteristically deforms of the head occurred. The caput succedaneum is over the fore head and may be so extensive that identification of the brow by palpation is impossible.
If the labor is possible the cardinal movements in brow presentation are:
1. Deflexion. The frontal suture is in the transverse size of the pelvic inlet. The head fixes to the inlet and deflexed. The middle of the frontal suture becomes the leading point.
2. Internal rotation.
3. Flexion of the head.
4. Extension of the head.
5. Internal rotation of the fetal trunk and external rotation of the fetal head.
Face presentation - head is hyperextended so that the occiput is in contact with the fetal back and the chin (mentum) is presenting part.
Diagnosis. By abdominal palpation the occiput, the chin and the angle between the fetal back and the occiput can be easily palpated. The fetal heart sound are the loudest from the side of the fetal thorax. On vaginal palpation, the distinctive features of the face presentation are the mouth, nose, the malar bones, and the orbital ridges.
Face presentation is rarely observed above the pelvic inlet. The brow generally presents and is converted to a face presentation after further extension of the head during descent through the pelvis.
The cardinal movements of labor in face posterior presentation are:
1. Deflexion. The face linea is in the transverse size of the pelvic inlet. Descent is brought about by the same factors as vertex presentation. The head presented its vertical diameter. The chin is the leading point.
2. Internal rotation. The object of internal rotation of the face is to bring the chin under the symphysis. Only in this way the neck subtend the posterior surface of the symphysis pubis. If the chin rotates directly posteriorly, the birth of the head is impossible.
3. Extension of the head. After the rotation and descent, the chin and mouth appear at the vulva, the undersurface of the chin presses against the symphysis, and the head is delivered by flexion. The nose, eyes, brow and occiput then appeared in succession over the anterior margin of the perineum.
4. Internal rotation of the fetal trunk and external rotation of the fetal head. The shoulders are born as in vertex presentations.
In face anterior presentation- cesarean section is performed because of risk of cephalopelvic disproportion.
Synclitism and asynclitism. Synclitism is a position when the sagittal suture is in the transverse pelvic diameter. The sagittal suture lies exactly midway between the symphysis and promontory.
If the sagittal suture approaches the sacral promontory, more of the anterior parietal bone presents itself to the examining fingers and the condition is called anterior asynclitism. If the sagittal suture lies close to the symphysis more of the posterior parietal bone presents and the condition is called posterior asynclitism.