Influence of pelvic outlet capacity on labor. A prospective pelvimetry study of 1,429 unselected primiparas

The influence of pelvic outlet capacity on labor and the efficiency of routine low-dose radiological pelvimetry to anticipate dystocia during labor were studied prospectively among 1,429 unselected term primiparas, all having fetal head presentation and normal pregnancy. Outlet contraction was found in 0.9% and borderline outlet measurement in 5.3%. In 1,402 cases labor started spontaneously and 83 emergency cesarean sections were done. The incidence of cesarean section because of dystocia increased in inverse proportion to decreasing pelvic outlet capacity. The incidence of other emergency cesarean sections was not influenced by pelvic outlet size. In 79% of cesarean section interventions due to dystocia, pelvic outlet capacity was normal. Apgar score less than 7 at one minute was more commonly associated with a small pelvic outlet. Apgar score at 5 minutes and neonatal morbidity were not influenced by pelvic outlet size. Pelvic outlet capacity had a marked influence on the mode of delivery, but the practical value of radiological pelvimetry by fetal head presentation is rarely considered, except in very selected cases.     

Brow and face presentations

Experience with 50 face and 34 brow presentations of the fetus at delivery in the Mayo Clinic agrees with that reported by others. The presence of a small pelvis, a small fetus, a large fetus, cranial abnormalities, placenta previa or a low-lying placenta, and twins seemed to contribute alone or in combination to the occurrence of these deflection attitudes. Premature rupture of membranes, looping of the cord, hydramnios, and pelvic tumors were not as common in this series as in others.The possibility of face or brow presentation should be kept in mind when the fetal head remains high during labor as well as when the fetal cephalic prominence is palpated on the same side as the fetal back. With early recognition and proper management, such a presentation should mean little, if any, additional risk to the mother or fetus. The patient should be given a trial of labor with frequent evaluation of uterine contractions and physical status of mother and fetus, with careful observation of progress during labor. Unless there is arrest of labor or signs of maternal or fetal distress, most of these patients can be expected to be delivered vaginally. Prolonged labor from combined dystocia and uterine inertia was common both in patients with face presentation and in those with brow presentation, but most of these also were delivered vaginally.Manual and forceps rotation or flexion or further extension of the extended fetal head is occasionally successful in converting the presentation to a more favorable one so that subsequent vaginal delivery becomes possible. The most frequent need for cesarean section in this series arose in the primiparas, particularly in those with the fetus in the mentoposterior position.     

Le suivi échographique de la deuxième partie du travail

In the second stage of labor, fetal head rotation and fetal head position are determinant for the management of labor to attempt a vaginal delivery or a cesarean section. However, digital examination is highly subjective. Nowadays, delivery rooms are often equipped with compact and high performance ultrasound systems. The clinical examination can be easily completed by quantified and reproducible methods. Transabdominal ultrasonography is a well-known and efficient way to determine the fetal head position. Nevertheless, ultrasound approach to assess fetal head descent is less widespread. We can use translabial or transperineal way to evaluate fetal head position. We describe precisely two different types of methods: the linear methods (3 different types) and the angles of progression (4 different types of measurement). Among all those methods, the main pelvic landmarks are the symphysis pubis and the fetal skull. The angle of progression appears promising but the assessment was restricted to occipitoanterior fetal position cases. In the coming years, ultrasound will likely play a greater role in the management of labor.     

Use of the soft, silicone obstetric vacuum cup for delivery of the fetal head at cesarean section

Delivery of the fetal head at cesarean section can sometimes be very difficult, and serious maternal and fetal complications may occur. Recently a new soft, silicone obstetric vacuum cup was introduced for use on the fetal head at vaginal delivery. In 35 cases the cup was used for delivery of the fetal head at cesarean section. It is an effective, harmless alternative to conventional devices, especially in aiding the delivery of the high-floating head occurring spontaneously or occurring after the head impacted deep in the pelvis is dislodged.     

Features of shoulder dystocia in a busy obstetric unit.

OBJECTIVE: To assess the incidence and complications of shoulder dystocia and whether those complications could be avoided. STUDY DESIGN: Retrospective analysis of shoulder dystocia between 1996 and 1999 to determine whether macrosomia, diabetes, height of head at full dilatation, length of second stage or instrumental delivery could predict shoulder dystocia. Fetal asphyxia, brachial plexus injury, maneuvers used to free the shoulders and experience of the attendant were also assessed. RESULTS: There were 56 cases of shoulder dystocia in 24,000 births, 59% after spontaneous delivery. McRoberts maneuver was used in 48 deliveries but sufficed as a solitary procedure in nine cases. The addition of suprapubic pressure was sufficient for 25 patients and 27 when bilateral episiotomy was also used. Corkscrew procedures were required in 12 patients. Midwives were involved in 35 cases and required assistance in 27. Macrosomia > 4,000 g was a feature in 20 infants and diabetes in 6. Neither the height of the head nor the length of the second stage was helpful. There were 13 cases of Erb's palsy, seven after vacuum delivery and six after spontaneous delivery. Eight of these cases were associated with McRoberts procedure and suprapubic pressure, two with no procedure and three with the corkscrew procedure. CONCLUSION: If all infants > 4,000 g had been delivered by cesarean section, there still would have been 36 cases of shoulder dystocia. If the ultrasonically estimated weight were used to select patients for cesarean section, seven cases would have been diagnosed. To lessen the degree and incidence of fetal injury, labor ward staff are urged to become as familiar as possible with the techniques of freeing the shoulders.     

Difficult delivery of the impacted fetal head during cesarean section: intraoperative disengagement dystocia

Cesarean section is commonly perceived as a simple and safe alternative to difficult vaginal birth. However, several trends in obstetrical practice may act in concert to cause impaction of the fetal head during the second stage of labor or, more commonly, following failed instrumental delivery. Subsequently, difficult and potentially traumatic disengagement of the deeply wedged head during cesarean section occurs. The maneuvers to disengage the wedged head include pushing (bimanual or by an assistant) the head through the vagina or, alternatively, pulling the infant's feet through the uterine incision. Although both methods may cause serious maternal and neonatal complications, available data seem to favor the pulling method and better outcome seems to depend on adequate uterine relaxation, the patient's position during operation, and special attention to the uterine incision. More data are needed to establish the frequency and extent of intraoperative disengagement dystocia and to determine the management protocol that carries the lowest risk in such circumstances.     

The cephalopelvic disproportion index. Combined fetal sonography and x-ray pelvimetry for early detection of cephalopelvic disproportion

The smallest pelvic diameter (either the anteroposterior of the inlet or the bispinal of the midpelvis) was determined with x-ray pelvimetry and compared to the biparietal diameter of the fetal head at term as determined with sonography. The difference between the two indicates how much wider the smallest diameter of the bony pelvis is than the fetal skull and was termed the cephalopelvic disproportion index. Vaginal delivery was impossible when the index was less than 9 mm and impossible or very difficult when between 9 and 12 mm. When it was greater than or equal to 13 mm, 26% needed a cesarean section, 19% had a difficult vaginal delivery, and the rest delivered vaginally with minimal or no difficulty. This technique clearly indicates when a vaginal delivery is impossible (index less than 9 mm) or very difficult (index less than 13 mm). The specificity was 100%. The index therefore can recognize, before labor, the cases of obvious cephalopelvic disproportion that contraindicate a trial of labor. It does not indicate, however, if a vaginal delivery is possible in the setting of a high index (sensitivity, 51%) because of the interference of other factors besides the cephalic and pelvic bony dimensions considered here. The index may prove most important in determining if a vaginal birth should occur after a cesarean section because it can clearly identify some patients who need a repeat cesarean section.     

505例巨大胎儿分析

目的 探讨巨大胎儿的产前诊断及分娩方式,降低母儿并发症。方法 回顾分析５０５例巨大胎儿诊断、分娩方式及并发症,并与单胎正常体重儿分娩情况进行比较。结果 巨大胎儿中双顶径（ＢＰＤ）＋胎骨长度（ＦＬ）〉１６．５ｃｍ者占８８．４６％,剖宫产组较阴道分娩组新生儿窒息率及产伤机会均明显降低,巨大胎儿与正常体重儿相比难产率明显升高。结论 ＢＰＤ＋ＦＬ〉１６．５ｃｍ可做为产前诊断巨大胎儿的一项可靠指标,对巨大胎     

The risk of shoulder dystocia related permanent fetal injury in relation to birth weight

OBJECTIVE: To examine birth weight related risks of fetal injury in connection with shoulder dystocia. STUDY DESIGN: The investigation was based on a retrospective analysis of 316 fetal neurological injuries associated with deliveries complicated by arrest of the shoulders that occurred across the United States. RESULTS: The study revealed that the distribution of birthweights for the high risk shoulder dystocia population differs from the standard birthweight distribution. The relative difference per birthweight interval is used to adjust an assumed 1:1000 baseline risk of injury due to shoulder dystocia following vaginal deliveries. These adjusted risks show a need to consider new thresholds for elective cesarean delivery. CONCLUSIONS: Current North American and British guidelines, that set 5000 g as minimum estimated fetal weight limit for elective cesarean section in non-diabetic and 4500 g for diabetic gravidas, may expose some macrosomic fetuses to a high risk of permanent neurological damage. The authors present the opinion that the mother, having been informed of the risks of vaginal versus abdominal delivery, should be allowed to play an active role in the critical management decisions.     

Influence of the pelvic outlet capacity on fetal head presentation at delivery

The influence of pelvic outlet capacity on fetal head presentation in 1,402 term primiparas with normal pregnancies was studied. In all cases radiological pelvimetry was carried out and labor started spontaneously. Occiput posterior (OP) delivery occurred in 5.1%. As pelvic outlet capacity decreased an increased frequency of OP presentations and need for epidural anesthesia (EDA) was found. With OP presentation the duration of labour was longer, the frequency of EDA, instrumental delivery, cesarean section and low Apgar score at 1 minute were all higher, all compared with occiput anterior (OA) presentation. No difference in fetal morbidity was found. When the influence of the pelvic outlet capacity was eliminated through comparison of matched groups, the course of delivery became more similar whether the presentation was OA or OP and the frequency of EDA became the same. Reduced pelvic outlet capacity seemed to be one cause of both OP presentation and the use of EDA.     

A multicenter controlled trial of fetal pulse oximetry in the intrapartum management of nonreassuring fetal heart rate patterns

OBJECTIVE: Recent developments permit the use of pulse oximetry to evaluate fetal oxygenation in labor. We tested the hypothesis that the addition of fetal pulse oximetry in the evaluation of abnormal fetal heart rate patterns in labor improves the accuracy of fetal assessment and allows safe reduction of cesarean deliveries performed because of nonreassuring fetal status. STUDY DESIGN: A randomized, controlled trial was conducted concurrently in 9 centers. The patients had term pregnancies and were in active labor when abnormal fetal heart rate patterns developed. The patients were randomized to electronic fetal heart rate monitoring alone (control group) or to the combination of electronic fetal monitoring and continuous fetal pulse oximetry (study group). The primary outcome was a reduction in cesarean deliveries for nonreassuring fetal status as a measure of improved accuracy of assessment of fetal oxygenation. RESULTS: A total of 1010 patients were randomized, 502 to the control group and 508 to the study group. There was a reduction of >50% in the number of cesarean deliveries performed because of nonreassuring fetal status in the study group (study, 4. 5%; vs. control, 10.2%; P =.007). However, there was no net difference in overall cesarean delivery rates (study, n = 147 [29%]; vs. control, 130 [26%]; P = .49) because of an increase in cesarean deliveries performed because of dystocia in the study group. In a blinded partogram analysis 89% of the study patients and 91% of the control patients who had a cesarean delivery because of dystocia met defined criteria for actual dystocia. There was no difference between the 2 groups in adverse maternal or neonatal outcomes. In terms of the operative intervention for nonreassuring fetal status, there was an improvement in both the sensitivity and the specificity for the study group compared with the control group for the end points of metabolic acidosis and need for resuscitation. CONCLUSION: The study confirmed its primary hypothesis of a safe reduction in cesarean deliveries performed because of nonreassuring fetal status. However, the addition of fetal pulse oximetry did not result in an overall reduction in cesarean deliveries. The increase in cesarean deliveries because of dystocia in the study group did appear to result from a well-documented arrest of labor. Fetal pulse oximetry improved the obstetrician's ability to more appropriately intervene by cesarean or operative vaginal delivery for fetuses who were actually depressed and acidotic. The unexpected increase in operative delivery for dystocia in the study group is of concern and remains to be explained.     

Abdominovaginal delivery: modification of the cesarean section operation to facilitate delivery of the impacted head

The abdominovaginal delivery is a modification of the cesarean section operation in the presence of an impacted fetal head, usually after a prolonged second stage of labor with ruptured membranes. With the legs abducted in either the "Whitmore" or the "frog" position, the wedged vertex is gently lifted with the cupped hand into the open transverse uterine incision, thereby reducing injury to the fetal head and the uterus. With the greater use of cesarean section operation and the sharp reduction in rotational and midforceps deliveries, the abdominovaginal procedure has an increasingly important place in our obstetric armamentarium.     

Breech deliveries and cesarean section

Breech presentation is the most common malpresentation, with about 3-4% of singleton fetuses presenting breech at delivery. Management of breech presentation has been a contentious issue with a lowering threshold for cesarean section in recent years. Perinatal mortality and morbidity are estimated to be three times that of comparable infants with vertex presentation. Breech presentation is commonly associated with certain adverse maternal and fetal factors which inherently give rise to increased perinatal morbidity and mortality. At present, most obstetricians favor cesarean delivery for uncomplicated pre-term breech. Controlled prospective studies have shown that the outcome of breech fetuses weighing more than 1500 g was not dependent on the mode of delivery. A more recent review from the Cochrane database by Grant does not justify a policy of elective cesarean section for pre-term breech. Vaginal delivery is preferred if the following criteria are met: frank breech only, estimated fetal weight of 2500-3500 g, adequate pelvimetry without hyperextended head, normal progression of labor, no evidence of fetal hypoxia under continuous fetal monitoring, and maternal weight under 90 kg. Vaginal delivery of frank breech at term may be just as safe as cesarean section when careful selection criteria are used. If these criteria are not fulfilled, or fetal monitoring cannot be performed, cesarean section is advisable.     

Breech vaginal delivery at or near term

Three percent to 4% of term fetuses will be breech at delivery. Evidence from randomized controlled trials has found a policy of planned cesarean section to be significantly better for the singleton fetus in breech presentation at term compared to a policy of planned vaginal birth. However, some women may wish to avoid cesarean section and for others, cesarean section may not be possible. We undertook this review to identify factors associated with higher and lower risk of adverse fetal or neonatal outcome at term during vaginal breech delivery. We searched MEDLINE from 1966 to 2002 using the search terms vaginal breech delivery and breech presentation and retrieved all relevant articles. We also reviewed personal references and reference lists of articles retrieved. Women who are older or who have a fetus that is either in footling presentation, has a hyperextended head or is estimated to weigh <2500 g or >4000 g may be at higher risk of adverse fetal outcome. Prolonged labor or not having an experienced clinician at vaginal breech birth may also increase the risk. Women with a fetus in breech presentation at term should be offered the option of delivery by planned cesarean section and should be informed that this will reduce their risk of adverse fetal or neonatal outcome. Practitioners should develop and maintain skills at vaginal breech delivery for those women not wishing or not able to be delivered by cesarean section.     

Multiple laparotomic myomectomy during pregnancy: a case report

The presence of uterine myomas during pregnancy is considered a risk factor for gestation and delivery. In literature, myomas are related to spontaneous abortion, bleeding, PPROM, preterm delivery, placenta previa, placental abruption, fetal malpresentations, mechanical dystocia and high incidence of cesarean section. Laparotomic myomectomy done during pregnancy is indicated when symptoms related to uterine myomas, as acute pelvic pain or gastroenteric or urinary symptoms, persist despite the pharmacological therapy. The purpose of this study is to show a successful surgical management of uterine myomas at 15.5 weeks of pregnancy, which allowed the continuation of gestation and a delivery without major complications.     

预防初次剖宫产指南对促进阴道试产的作用

剖宫产术是处理妊娠并发症和合并症、解决难产和宫内缺氧的重要手段。但近年剖宫产率的上升并未明显降低孕产妇和围产儿发病率及死亡率,相反增加了剖宫产术后并发症的发生率。文章分析剖宫产的风险,从孕期管理,个性化引产,提高助产技术,新产程的运用,胎儿监护的管理,臀位外倒转以及剖宫产后阴道试产等7个方面阐述有关预防剖宫产、促进阴道试产问题。     

Pelvic floor dysfunction,and effects of pregnancy and mode of delivery on pelvic floor

Pelvic floor dysfunction (PFD), although seems to be simple, is a complex process that develops secondary to multifactorial factors. The incidence of PFD is increasing with increasing life expectancy. PFD is a term that refers to a broad range of clinical scenarios, including lower urinary tract excretory and defecation disorders, such as urinary and anal incontinence, overactive bladder, and pelvic organ prolapse, as well as sexual disorders. It is a financial burden on the health care system and disrupts women's quality of life. Strategies applied to decrease PFD are focused on the course of pregnancy, mode and management of delivery, and pelvic exercise methods. Many studies in the literature define traumatic birth, usage of forceps, length of the second stage of delivery, and sphincter damage as modifiable risk factors for PFD. Maternal age, fetal position, and fetal head circumference are nonmodifiable risk factors. Although numerous studies show that vaginal delivery affects pelvic floor structures and their functions in a negative way, there is not enough scientific evidence to recommend elective cesarean delivery in order to prevent development of PFD. PFD is a heterogeneous pathological condition, and the effects of pregnancy, vaginal delivery, cesarean delivery, and possible risk factors of PFD may be different from each other. Observational studies have identified certain obstetrical exposures as risk factors for pelvic floor disorders. These factors often coexist; therefore, the isolated effects of these variables on the pelvic floor are difficult to study. The routine use of episiotomy for many years in order to prevent PFD is not recommended anymore; episiotomy should be used in selected cases, and the mediolateral procedures should be used if needed.     

Obstetrical brachial plexus palsy--etiopathogenesis, risk factors, prevention, prognosis

Obstetrical brachial plexus palsy (OBP) complicates a small proportion of births. The incidence is believed to be 0.35 to 5 cases per 1000 live births. Risk factors of OBP included: 1/ large birth weight, 2/ shoulder dystocia and prolonged second stage of labour , 3/ instrumental vaginal delivery (forceps delivery, vacuum extraction), 4/ diabetes mellitus and mother's obesity, 5/ breech presentation, 6/ delivery an infant with OBP in an antecedent delivery. Historically, the cause of OBP was excessive lateral traction applied to the fetal head at delivery, in association with anterior shoulder dystocia. Not all cases of brachial plexus palsy are attributable to traction. Brachial plexus injury may be occurring in the absence of shoulder dystocia, in the posterior arm of infants with anterior shoulder dystocia and can be associated with cesarean delivery. Intrauterine factors may play some role in the etiology of the OBP. Many strategies have been proposed to prevent the occurrence of OBP--control of the birth weight, induction of labour, cesarean delivery, intensified management of gestational diabetes. About 10-20% of patients with injuries of the brachial plexus require surgical intervention for optimal results.     

Occipito-posterior fetal head position, maternal and neonatal outcome

The purpose of this review is to summarize the available evidence on occipito-posterior fetal head position and maternal and neonatal outcome. The occipito-posterior fetal head position is the most common malposition, but there are not so many data about it in literature. Its incidence is ranging from 1.8% by Fitzpatrick, to 4.6% and 5.5% by Yancey and Sizer, to 6% by Ponkey. Only two trials studied the occipito-posterior associated factors. There are lower incidence of premature rupture of membrane, arterial hypertension pregnancy-induced, induced labour, increased of episiotomy, instrumental delivery and a decreased of vaginal birth without a difference in neonatal Apgar, and with a neonatal bigger weight. The occipito-posterior fetal head position persistence compared to anterior position, has a statistically significant association with low maternal stature, previous cesarean section, longer first and second stage of labour, oxytocin augmentation, epidural analgesia, instrumental vaginal delivery, chorion-amniositis, vaginal perineal injures, loss of blood and post partum infections. A highest incidence of occipito-posterior fetal head position may depend by nulliparity, malnutrition with pelvic deformity, pelvic immaturity in the teenager and anterior placenta. Epidural analgesia is a risk factor for fetal head malposition. The majority of occipito-posterior fetal head positions is not due to a malrotation, but to a persistence in this position of the fetal head. In fact, this persistence leads to a failure of the fetal head rotation. The prolonged second stage is often the result of occipito-posterior fetal head position and instrumental delivery is required. The traditional vaginal examination is not useful for the determination of fetal head position, so and instrumental method is needed, such as ultrasound, for a correct evaluation of fetal head position, particularly if a vaginal instrumental delivery is necessary. This is recommended by the Canadian Society of Obstetrics and Gynecology. The evaluation of fetal head position is important in the prediction of labour induction.     

Adverse perinatal events and subsequent cesarean rate.

OBJECTIVE: To determine whether severe intrapartum complications resulting in poor neonatal outcome increased obstetricians' cesarean delivery rates. METHODS: From July 1996 through June 1998 we prospectively studied 3008 deliveries by 12 obstetricians. We chose adverse neonatal outcomes that would be viewed by obstetricians as anxiety-provoking experiences that are rare in obstetric practice. Index events included head entrapment of breech infants, Apgar score less than 3 at 10 minutes, shoulder dystocia resulting in persistent brachial plexus injury, and intrapartum fetal death. After an index event was identified, the obstetrician's cesarean delivery rate for the 50 deliveries before the index event was compared with the 50 deliveries after the index event. Obstetricians who had no intrapartum complication during the observational period were matched as controls. RESULTS: Six index events were identified, three cases of shoulder dystocia and three intrapartum fetal deaths. In three of these six cases, the Apgar score at 10 minutes was less than 3. Obstetricians who attended a delivery with severe intrapartum complications had an average increase in their cesarean delivery rate of 37% in the 50 deliveries after the index event (21.0% to 28.7%, P < .05). This rate was greater (P < .05) than that of matched control obstetricians observed during the same observation period (19.0% to 18.7%). CONCLUSION: Intrapartum complications such as persistent neonatal brachial plexus injury or fetal death increased the cesarean delivery rate of the obstetrician experiencing these events. Obstetricians should be aware of the effect of these adverse events on their practice of obstetrics.