A randomised prospective study comparing the new vacuum extractor policy with forceps delivery

Recurrent Risk of Anal Sphincter Laceration Among Women With Vaginal Deliveries

OBJECTIVE

The first aim of this study was to estimate the impact of anal sphincter laceration during the first delivery on the risk of recurrence in the second delivery. The second aim was to estimate the absolute risk of anal sphincter laceration in the second delivery according to the history of anal sphincter laceration and birth weight.

METHODS

In this population-based cohort study, the study sample comprised all women included in the Norwegian Medical Birth Registry with 2 consecutive singleton vaginal deliveries during the period 1967-1998 (n = 486,463). The impact of prior anal sphincter laceration on recurrent anal sphincter laceration was estimated as crude and adjusted odds ratios (ORs).

RESULTS

Anal sphincter laceration during first delivery increased the risk for a sphincter laceration in the next delivery, (adjusted OR 4.3, 95% confidence interval [CI] 3.8-4.8). Other risk factors were birth weight (adjusted OR 23.6, 95% CI 16.5-33.6, birth weight > 5,000 g versus birth weight < 3,000 grams), use of forceps (adjusted OR 5.1, 95% CI 4.3-6.0), use of vacuum (adjusted OR 1.4, 95% CI 1.1-1.7), and period of delivery (adjusted OR 4.3, 95% CI 3.7-5.0 for 1995-1998 versus 1967-1975). The absolute risks for anal sphincter laceration at second delivery for women with prior laceration were 1.3% (95% CI 0.4-3.2%) for birth weight less than 3,000 g and 23.3% (95% CI 11.8-38.6%) for birth weight more than 5,000 g.

CONCLUSION

Only 10% of women with anal sphincter laceration at second delivery had a history of prior laceration. Prior anal sphincter laceration is associated with increased risk of laceration in second delivery, in particular in women who carry children with high birth weight.

LEVEL OF EVIDENCE

II-2.

Failed instrumental delivery: how safe is the use of a second instrument?

An audit of failed instrumental deliveries was undertaken to assess the incidence of complications and the adequacy of documentation. When one instrument has failed to effect delivery, the use of a second instrument could in most cases be used to complete the delivery without harm to the mother or baby. However in a small but significant number of cases there are severe maternal or perinatal complications, and these could be the subject of litigation. This could be avoided by adequate pre-application assessment, standard conduct of instrumental delivery and full documentation. Inadequate documentation could be overcome by the use of a pro forma. Selective use of plastic and metal cups could reduce the incidence of failed attempts.

Does the attending obstetrician influence the mode of delivery in the 'standard' nullipara?

We have investigated whether the attending obstetrician has an influence on the mode of operative delivery by examining practices of obstetricians working at a district general hospital in the United Kingdom over 3 years. Nulliparous women ( n = 1410) with a singleton, cephalic and term fetus who had an operative delivery were studied. The most senior obstetrician present at 89% of these deliveries was one of the 12 registrars training in the unit. The proportion of women delivered by each mode of vaginal or abdominal operative delivery by each registrar was compared. In nine of these registrars the proportion of women they delivered by at least one mode differed significantly from the others. Caesarean section after an unsuccessful attempt at operative vaginal delivery showed the largest variation and caesarean section before the second stage of labour showed the least, with vaginal operative delivery modes and caesarean section in the second stage without a trial of vaginal delivery intermediate between the two. The method can be used to provide a 'profile' of the preferences exercised by individual operators.

Operative vaginal delivery: a comparison of forceps and vacuum for success rate and risk of rectal sphincter injury

OBJECTIVE

We investigated the success rate of operative vaginal delivery and risk of rectal sphincter injury when forceps or vacuum was used.

STUDY DESIGN

Cases were identified by a retrospective review of delivery logbooks and an obstetric database. Rotations were excluded. Failure was defined as inability to deliver the fetus with the initial instrument. Rectal injury was defined as third- or fourth-degree laceration. Institutional review board approval was obtained. P-value of less than .05 was considered significant, and odds ratios (OR) were calculated when appropriate.

RESULTS

Data were obtained for 1802 deliveries: 1438 occiput anterior and 364 occiput posterior positions. For occiput anterior position, rectal sphincter injury with forceps was 53.8% and vacuum 26.6% (P < .0001, OR 3.25). Failure rate with vacuum was 6.3% and forceps 0.9% (P < .0001, OR 7.53). For occiput posterior position, rectal injury with forceps was 71.6% and vacuum 33.1% (P < .0001; OR 5.25). Failure rate with vacuum was 33.0% and with forceps 13.6% (P < .0001, OR 3.15). For occiput posterior position, failure rate at mid position with vacuum was 71.4%, and forceps 16.7% (P < .001, OR 12.5). Failure rate at low position with vacuum was 30.8%, and forceps 12.5% (P < .001, OR 3.14). Failure rate with vacuum at mid position was higher than at low position (P < .0001, OR 5.57). Failure rate with forceps at mid and low positions was not significantly different. There was no difference in failure rate between vacuum and forceps at the outlet position.

CONCLUSIONS

For both occiput anterior and posterior cases, the use of forceps was associated with a higher success rate than the vacuum, but with greater risk of rectal sphincter injury. The use of either vacuum or forceps from the occiput posterior position was associated with a higher likelihood of rectal injury and lower likelihood of vaginal delivery when compared with the occiput anterior position.

[Complications of vacuum extractor deliveries]

OBJECTIVES

To describe maternal and neonatal complications following deliveries assisted by vacuum extraction and to compare outcomes with those obtained after spontaneous vaginal delivery. We wanted to know if vacuum extractor was a risk factor by itself.

MATERIALS AND METHODS

We conducted a retrospective study of two years activity involving 4524 deliveries of which 845 (18.7%) were vacuum extractor assisted. We precisely defined maternal and neonatal complications to compare their rates in spontaneous vaginal delivery and vacuum extractor groups.

RESULTS

There were 1333 maternal complications and 114 neonatal complications. The adjusted risks of maternal complications were significantly higher in the vacuum extractor group for simple vaginal tears (OR=3.0; p<0.001), the simple perineal tears (OR=1.8; p<0.001) and third degree perineal tears (OR=2.7; p<0.01). For neonatal complications, the difference was significant for cephalhematomas (OR=10; p<0.001) and scalp abrasions (OR=53; p<0.001). No cases of skull fracture or subgaleal subaponeurotic hemorrhage were recorded.

CONCLUSION

Our rates of maternal and neonatal complications after vacuum extractor were similar to those described in the literature. We have been able to show that vacuum extraction is itself a risk factor for third degree perineal tears and cephalhematoma. However, these complications are so infrequent that the advantages of this method of extraction argue in favor of wide use in obstetrics.

Guidelines for Operative Vaginal Birth

OBJECTIVE

To provide guidelines for operative vaginal birth in the management of the second stage of labour.

OPTIONS

Non-operative techniques, episiotomy, and Caesarean section are compared to operative vaginal birth. outcome: Reduced fetal and maternal morbidity and mortality.

EVIDENCE

MEDLINE and Cochrane databases were searched using the key words 'vacuum' and 'birth' as well as 'forceps' and 'birth' for literature published in English from January 1970 to June 2004. The level of evidence and quality of recommendations made are described using the Evaluation of Evidence from the Canadian Task Force on the Periodic Health Examination.

RECOMMENDATIONS

1. Non-operative interventions such as one-to-one support, partogram use, oxytocin use, and delayed pushing in women using epidurals will decrease need for operative birth. (I-A) 2. Manual rotation may be used alone or in conjunction with instrumental birth with little or no increased risk to the pregnant woman or to the fetus. (III-B) 3. Routine episiotomy is not necessary for an assisted vaginal birth. (II-1E) 4. When operative intervention in the second stage of labour is required, the options, risks, and benefits of vacuum, forceps, and Caesarean section must be considered. The choice of intervention needs to be individualized, as one is not clearly safer or more effective than the other. (II-B) 5. Failure of the chosen method, vacuum and/or forceps, to achieve delivery of the fetus in a reasonable time should be considered an indication for abandonment of the method. (III-C) 6. Adequate clinical experience and appropriate training of the operator are essential to the safe performance of operative deliveries. Hospital credentialing boards should grant privileges for performing these techniques only to an appropriately trained individual who demonstrates adequate skills. (III-C).

VALIDATION

The Clinical Practice Obstetrics Committee and Executive and Council of the Society of Obstetricians and Gynaecologists of Canada approved these guidelines.

Anal endosonography and its role in assessing the incontinent patient

Anal endosonography is now recognized as an important investigation in the assessment of faecal incontinence. The endosonographer needs to be aware that the anatomy of the anal sphincter is complex and therefore there can be pitfalls in the interpretation of images. The findings have clinical implications on subsequent management and can contribute to prognosticating outcome. However, anal endosonography has a complementary role and other investigations, such as anal manometry, should be performed before intervention.

Operative vaginal delivery and neonatal and infant adverse outcomes: population based retrospective analysis

OBJECTIVE

To compare the risk of neonatal and infant adverse outcomes between vacuum and forceps assisted deliveries.

DESIGN

Population based study.

SETTING

US linked natality and mortality birth cohort file and the New Jersey linked natality, mortality, and hospital discharge summary birth cohort file.

PARTICIPANTS

Singleton live births in the United States (n = 11 639 388) and New Jersey (n = 375 351).

MAIN OUTCOME MEASURES

Neonatal morbidity and mortality.

RESULTS

Neonatal mortality was comparable between vacuum and forceps deliveries in US births (odds ratio 0.94, 95% confidence interval 0.79 to 1.12). Vacuum delivery was associated with a lower risk of birth injuries (0.69, 0.66 to 0.72), neonatal seizures (0.78, 0.68 to 0.90), and need for assisted ventilation (< 30 minutes 0.94, 0.92 to 0.97; > or = 30 minutes 0.92, 0.88 to 0.98). Among births in New Jersey, vacuum extraction was more likely than forceps to be complicated by postpartum haemorrhage (1.22, 1.07 to 1.39) and shoulder dystocia (2.00, 1.62 to 2.48). The risks of intracranial haemorrhage, difficulty with feeding, and retinal haemorrhage were comparable between both modes of delivery. The sequential use of vacuum and forceps was associated with an increased risk of need for mechanical ventilation in the infant and third and fourth degree perineal tears.

CONCLUSION

Although vacuum extraction does have risks, it remains a safe alternative to forceps delivery.

Incontinences urinaires et anales post-obstétricales : facteurs de risque et prévention

OBJECTIVE

This study was undertaken to review the available data on urinary and fecal incontinence and their association with maternal as well as fetal per partum characteristics.

METHOD

A Pubmed (Medline search performed between 1999 and 2003 using "urinary incontinence and delivery" and "fecal incontinence and delivery" identified 501 relevant papers. Most of them are retrospective analyses whereas few are randomized controlled trials (RCT).

RESULTS

Two studies performed with computer-stored databases analyzed the risk factors of incontinence among 2,886,126 deliveries. Primiparity, birthweight over 4000 g and all types of assisted vaginal deliveries significantly increased the risk of anal sphincter damage. Results concerning the effect of episiotomy are conflicting. Controlled randomized trials have shown that pelvic floor muscle training during pregnancy as well as planned cesarean section significantly and moderately decrease the risk of urinary incontinence. The only RCT available has shown that planned cesarean section did not reduce significantly incontinence of flatus. Finally the only trial that compare surgical techniques used to repair the anal sphincter did not show any significant difference.

CONCLUSION

Risk factors for anal sphincter damage during delivery are well known. RCT focusing on how to prevent and how to cure fecal as well as urinary incontinence are urgently needed.

Can formal education and training improve the outcome of instrumental delivery?

OBJECTIVE(S)

The primary objective was to examine the effect of formal education and training on instrumental delivery with respect to its success rate and associated neonatal and maternal morbidity. The secondary objective was to determine factors that could influence the success rate of instrumental delivery.

STUDY DESIGN

Prospective case-control study with historical controls set in a teaching hospital in Sheffield. The prospective group included all women who had instrumental deliveries between 1 November 1999 and 29 February 2000. The control group included all women who delivered between 1 February 1997 and 1 February 1998. An educational package involving formal postgraduate training and self-directed learning were introduced in the time period between the prospective and the control groups. Medical notes were reviewed in the historical controls. For both the control and prospective groups, the following patient characteristics were recorded: maternal age, parity, whether or not onset of labour was induced, use of oxytocin in the second stage of labour, delay in the second stage, operator grade, vaginal findings at delivery and the use of epidural analgesia.

RESULTS

The overall failure rate was not different in the prospective group (16%) compared with the control group (18.5%). However, the introduction of an educational package was associated with significant decrease in maternal morbidity associated with cervical, severe labial and high vaginal tears (Odds Ratio (OR) 0.29, CI 0.09-0.97) and neonatal morbidity associated with admission to SCBU (OR 0.72, CI 0.02-0.60), severe neonatal scalp injury (OR 0.14, CI 0.02-0.98) and facial injuries (OR 0.02, CI 0.01-0.04). The factors identified to affect the success of instrumental deliveries were: OP and OT positions of the baby at delivery (OR 0.28, CI 0.17-0.44) and inexperienced operators (OR 0.11, CI 0.02-0.58).

CONCLUSION

In this study, formal education and training of medical staff did not influence the success rate of instrumental delivery but was associated with improved safety for both mother and baby.

Immediate Maternal and Neonatal Effects of Forceps and Vacuum-Assisted Deliveries

OBJECTIVE

To estimate the differences in immediate maternal and neonatal effects of forceps and vacuum-assisted deliveries.

METHODS

We conducted a medical record review of all forceps and vacuum-assisted deliveries that occurred from January 1, 1998, to August 30, 1999, at Winthrop-University Hospital. Maternal demographics and delivery characteristics were recorded. Maternal outcomes, such as use of episiotomy and presence of lacerations, were studied. Neonatal outcomes evaluated were Apgar scores, neonatal intensive care unit admissions, cephalohematomas, instrument marks and bruising, and caput and molding.

RESULTS

Of 508 operative vaginal deliveries, 200 were forceps and 308 were vacuum assisted. Forceps were used more often than vacuum for prolonged second stage of labor (P =.001). There was a higher rate of epidural (P =.02) and pudendal (P <.001) anesthesia, episiotomies (P =.01), maternal third- and fourth-degree perineal (P <.001) and vaginal lacerations (P =.004) with the use of forceps, whereas periurethral lacerations were more common in vacuum-assisted (P =.026) deliveries. More instrument marks and bruising (P <.001) were found in the neonates delivered by forceps, whereas there was a greater incidence of cephalohematomas (P =.03) and caput and molding (P <.001) in the neonates delivered with vacuum. Multivariable logistic regression analysis showed that forceps use was associated with an increase in major perineal and vaginal tears (odds ratio [OR] 1.85; 95% confidence interval [CI] 1.27, 2.69; P =.001), an increase in instrument marks and bruising (OR 4.63; 95% CI 2.90, 7.41; P <.001) and a decrease in cephalohematomas (OR 0.49; 95% CI 0.29, 0.83; P =.007) compared with the vacuum.

CONCLUSIONS

Maternal injuries are more common with the use of forceps. Neonates delivered with forceps have more facial injuries, whereas neonates delivered with vacuum have more cephalohematomas.

LEVEL OF EVIDENCE

II-3

Recurrent persistent occipito-posterior position in subsequent deliveries

A nine year follow up study of the delivery pattern of 119 women after delivery in the persistent occiput posterior position and their occipito-anterior controls. The studied parameters were: number of deliveries, number of repeated cases of persistent occiput posterior position and operative deliveries. Deliveries in the occipito-posterior position were more common in the study group than in the controls (P= 0.031). Except for this, no statistically significant differences were found between the groups. According to the results, recurrence of the persistent occiput posterior position is common. A history of delivery in the persistent occiput posterior position does not seem to have any major impact on future childbearing.

The influence of vacuum extractor on fetal oxygenation and newborn status

AIM

The aim of this study was to determine the effects of vacuum extractor assisted delivery on fetal oxygenation and acid-base balance.

METHODS

Sixty-one women were enrolled in the present study. The subjects were divided into two groups. Group A, consisting of 39 women, had normal vaginal deliveries. Group B, consisting of 22 women, underwent a vacuum extractor assisted vaginal delivery. Fetal arterial oxygen saturation (SpO2) monitoring was used in all women after full cervical dilatation. After delivery, umbilical artery pH, pCO2, pO2 and base deficit (BDecf) levels were determined in all neonates.

RESULTS

The mean FSpO2 value in Group A was 51.53+/-5.87% and in Group B 48.03+/-6.39% (p<0.03). The mean cord pH value in fetuses of Group A was 7.26+/-0.05, and in Group B 7.17+/-0.09. There was also a significant difference between the two groups with regards to mean pO2, pCO2 and BDecf values.

CONCLUSIONS

Vacuum assisted vaginal delivery was associated with lower fetal arterial oxygen saturation levels as well as lower cord blood pH values compared to those seen after unassisted vaginal delivery. Although decreased, however, the above parameters remained within normal ranges.

Childbirth-induced trauma to the urethral continence mechanism: review and recommendations

To summarize the literature on immediate pelvic floor damage from childbirth and episiotomy, a MEDLINE search of English language articles published from 1983 to 2001 was performed. Vaginal delivery causes varying degrees of muscular, neuromuscular, and connective tissue damage. This damage may result in urinary and/or fecal incontinence. Routine midline episiotomy increases the risk of third- and fourth-degree perineal lacerations, which may lead to fecal incontinence. Routine use of mediolateral episiotomy does not prevent urinary incontinence (UI) or severe perineal tears. It is possible to reduce the rate of mediolateral episiotomy to as low as 20% in primiparas without increasing the risk of anal sphincter damage. Control of obesity before delivery, as well as pelvic floor exercises and regular physical exercise both before and after delivery, seem to reduce the risk of postpartum UI.

Symptoms and anal sphincter morphology following primary repair of third-degree tears

Background

Approximately 0·6–9 per cent of vaginal deliveries are complicated by third-degree tears. The precise impact of such injuries on future pelvic floor function remains unknown. The aim of this study was to define the extent of structural and physiological damage to the anal sphincter and to investigate anorectal function in women who sustained third-degree tears during vaginal delivery.

Methods

Fifty-six women who sustained a third-degree tear were investigated prospectively. All patients had a primary repair of the anal sphincter complex, and were assessed by anorectal physiology and endoanal ultrasonography at a mean of 3·6 months. Symptoms were assessed by direct personal interview and also by a self-completed questionnaire.

Results

Forty-four patients had a persistent anal sphincter defect on ultrasonography. The mean resting and squeeze anal canal pressures were significantly lower in patients with a combined defect than in those in whom the repair was intact (P = 0·036 and P = 0·005 respectively). At direct interview three patients volunteered current symptoms of faecal and/or urinary incontinence whereas 32 reported bothersome symptoms on the questionnaire (P &lt; 0·001).

Conclusion

The anatomical and physiological damage sustained during third-degree tears appears to be much greater than is generally appreciated. Primary repair does not provide lasting integrity. A self-administered questionnaire appears to be more accurate in defining the symptomatology.

Extraction instrumentale en 2002 au sein du réseau AURORE : incidence et complications néo-natales graves

OBJECTIVES

The purpose of this study was to evaluate the incidence of forceps and vacuum application and the incidence of its related neonatal complications. This study was performed in a network of 37 maternity hospitals.

PATIENTS AND METHOD

A postal questionnaire was sent to 156 obstetricians between February and March 2003.

RESULTS

Response rate was 78%. In 2002 the operative vaginal delivery rate was 11.2% of all live births. Forceps are the primary instruments (6.3%) whereas vacuum delivery rate was 4.9%. One obstetrician never uses forceps while 38 (31%) never use vacuum. Only 29 (24%) report using both instruments frequently. During 2002 no neonatal death related to an operative vaginal delivery was reported while 145 neonatal complications were (3.2%). Major complications were one depressed skull fracture (1/4589) and 14 extensive caput succedaneum (14/4589). Minor complications were cutaneous lesions (124/4589) and facial palsy (6/4589). Vacuum delivery was associated with a significantly higher extensive caput succedaneum rate (P = 0.018) while the only depressed skull fracture observed was related to forceps use. Forceps delivery was associated with a significantly higher cutaneous lesions rate (P < 0.001).

DISCUSSION AND CONCLUSIONS

This study showed that, in 2002, operative vaginal deliveries still represent a significant amount of vaginal deliveries, a majority of obstetricians do not use both instrument and neonatal associated complications are frequent (3.2%) but rarely severe. Therefore, we believe that every method that allows a safe teaching of operative delivery should be promoted.

Urinary and anal incontinence after vacuum delivery

OBJECTIVES

To evaluate urinary and fecal incontinence symptoms, and occult anal sphincter defects in women after vacuum and spontaneous vaginal delivery.

STUDY DESIGN

In a case-control study, 50 primiparous women delivered by vacuum extraction were compared to 50 women delivered spontaneously. Urinary and anal incontinence symptoms, pelvic floor muscle strength and sphincter defects on endoanal ultrasound were evaluated 6-24 weeks postpartum.

RESULTS

New anal incontinence symptoms after childbirth were found in 30% of the vacuum group compared to 34% of the controls, new urinary incontinence symptoms in 28 and 42%, respectively (not significant). After excluding Grade III perineal tear, sonographic sphincter defects were found in 11 (27.5%) after vacuum delivery compared to 4 (10%) after spontaneous delivery (P<0.05, chi(2)-test).

CONCLUSION

Anal and urinary incontinence symptoms are frequent after vaginal delivery. Vacuum delivery causes more sonographic sphincter defects but appears to cause no more harm to pelvic floor function than spontaneous vaginal delivery.

The incidence, risk factors and obstetric outcome in primigravid women sustaining anal sphincter tears

BACKGROUND

The incidence of anal sphincter tears is highest among nulliparous women. The aim of this study was to ascertain if there were other factors that increased their risk.

METHODS

This was a retrospective study of all primigravid vaginal deliveries that had sustained an anal sphincter tear (n = 122), compared with deliveries that did not have this complication (n = 16,050). The study sample was drawn from a computerized maternity information database, comprising 52 916 deliveries in the South Glamorgan region during 1990-99. SPSS version 10 was used for statistical analysis.

RESULTS

The incidence of anal sphincter tears in this study population was 0.8% (122/16172). Postdates (OR = 1.8, 95% CI = 1.3-2.6) and fetal macrosomia (OR = 3.8, 2.4-6) together with induction of labor (OR = 1.5, 1.01-2.2), use of spinal analgesia at delivery (OR = 3.1, 1.1-8.4), assisted vaginal delivery (OR = 1.9, 1.3-2.7; especially the use of forceps, OR = 2.2, 1.3-3.9) and doctor-conducted deliveries (OR = 2.2, 1.6-3.2) were found to be associated with a significantly higher incidence of anal sphincter tears. Logistic regression revealed fetal macrosomia and doctor-conducted deliveries to be independent risk factors that, when occurring together, were associated with a fourfold increase in the risk of occurrence of anal sphincter tears.

CONCLUSIONS

This study suggests that careful assessment and counseling of women, particularly > 40 weeks gestation or those potentially having macrosomic fetuses, especially if forceps are to be used for prolonged second stage in primigravid women, may help to identify those at significant risk of anal sphincter tears.

Failed individual and sequential instrumental vaginal delivery: contributing risk factors and maternal-neonatal complications

BACKGROUND

To identify the risk factors for failed instrumental vaginal delivery, and to compare maternal and neonatal morbidity associated with failed individual and sequential instruments used.

DESIGN

A retrospective case-control study.

METHODS

From January 1995 to June 2001, there were 39 508 live births at >37 weeks' gestation of which 2628 (6.7%) instrumental vaginal deliveries were performed, 1723 (4.4%) were vacuum extractions and 905 (2.3%) were forceps. A total of 155/2628 (5.9%) patients who had failed instrumental delivery were matched with 204 patients who had successful instrumental delivery. The patients were divided into five groups. Group I (n = 129) had failed vacuum extraction, group II (n = 13) failed forceps, group III (n = 13) failed both (i.e. failed attempt at both instruments sequentially), group IV (n = 138) had successful vacuum extraction and group V (n = 66) successful forceps.

RESULTS

The failure rate for vacuum extractions 129/1723 (7.5%) was significantly higher than that for forceps 13/905 (1.4%) [odds ratio (OR) = 5.6, 95% CI 3-10.3]. There were no significant differences in all maternal complications (25.5% vs. 26.6%) between vacuum (groups I and IV) and forceps (groups II and V) assisted deliveries. There were more maternal complications in group III (46.2%) than in groups I (35.7%), II (23.1%) and V (27.3%) that did not reach statistical significance but were significantly higher than in group IV (15.9%, OR = 4.5, 95% CI 1.2-16.9). There was a significantly higher rate of all fetal complications in group III [11/13 (84.6%)] than in groups I [69/129 (53.5%)], II [7/13 (53.8%)], IV [35/138 (25.4%)] and V [22/66 (33.3%)] (OR = 4.8, 95% CI 0.9-19.9).

CONCLUSIONS

Applying the instrument at < or =0 fetal station, nulliparous women, history of previous cesarean section and fetal head other than occipitoanterior position were risk factors for failed instrumental delivery. Sequential use of instrumental delivery carries a significantly higher neonatal morbidity than when a single instrument is used.

Risk factors for perineal injury during delivery

OBJECTIVE

We sought to identify risk factors for anal sphincter injury during vaginal delivery.

STUDY DESIGN

This was a retrospective, case-control study. We reviewed 2078 records of vaginal deliveries within a 2-year period from May 1, 1999, through April 30, 2001. Cases (n = 91) during the study period were defined as parturients who had documentation of greater than a second-degree perineal injury. Control subjects (n = 176), who were identified with the use of a blinded protocol, included women who were delivered vaginally with less than or equal to a second-degree perineal injury. For each patient, we reviewed medical and obstetrics records for the following characteristics: maternal age, race, weight, gestational age, parity, tobacco use, duration of first and second stages of labor, use of oxytocin, use of forceps or vacuum, infant birth weight, epidural use, and episiotomy use.

RESULTS

Of the 2078 deliveries that were reviewed, we discovered 91 cases (4.4%) of documented anal sphincter injury. The mean maternal age of our sample was 24.9 +/- 5.9 years). Nearly two thirds (63.2%) were white; 26.7% were black, and 10.1% were of other racial backgrounds. Forceps were used in 51.6% of deliveries that resulted in tears (cases), compared to 8.6% of deliveries without significant tears (control subjects, P <.05). Using cases and control subjects with complete data (cases, 82; control subjects, 144), delivery with forceps was associated with a 10-fold increased risk of perineal injury (odds ratio, 10.8; 95% CI, 5.2-22.3) compared to noninstrumented deliveries. The association was similar after adjustment for age, race, parity, mode of delivery, tobacco use, episiotomy, duration of labor (stages 1 and 2), infant birth weight, epidural, and oxytocin use (odds ratio, 11.9; 95% CI, 4.7-30.4). Nulliparous women were at increased risk for tears (adjusted odds ratio, 10.0; 95% CI, 3.0-33.3) compared with multiparous patients, but parity did not reduce the association between forceps-assisted deliveries and anal sphincter injuries. Increasing fetal weight was also a risk factor in both unadjusted and adjusted analyses. The performance of a midline episiotomy was associated with an increased risk of anal sphincter tear compared with delivery without an episiotomy in the univariate analysis (odds ratio, 4.9; 95% CI, 2.5-9.6), but this association was reduced in the adjusted analysis (odds ratio, 2.5; 95% CI, 1.0-6.0). The increased duration of both the first and second stages of labor increased injury risk in the unadjusted, but not adjusted, analysis. No significant association was observed between case status and the use of oxytocin or epidural anesthesia. Greater, but not significant, increased risk was associated with maternal indications for operative delivery compared with fetal indications.

CONCLUSION

Our results are consistent with recent reports that identify forceps delivery and nulliparity as risk factors for recognized anal sphincter injury at the time of vaginal delivery. Further investigation should focus on the determination of whether the association of injury to instrumentation is causal or, in fact, modifiable. Because of the established association between sphincteric muscular damage and anal incontinence, patients should be counseled about the risk of anal sphincter injury when operative vaginal delivery is contemplated. Such patients should be followed closely in the postpartum setting to assess for the development of potential anorectal complaints.

Comparison of transvaginal digital examination with intrapartum sonography to determine fetal head position before instrumental delivery

OBJECTIVE

To investigate the accuracy of intrapartum transvaginal digital examination in defining the position of the fetal head before instrumental delivery.

PATIENTS AND METHODS

In 64 singleton pregnancies undergoing instrumental delivery the fetal head position was determined by transvaginal digital examination by the attending obstetrician. Immediately after or before the clinical examination, the fetal head position was determined by transabdominal ultrasound by a trained sonographer who was not aware of the clinical findings. The digital examination was considered to be correct if the fetal head position was within +/- 45 degrees of the ultrasound finding. The accuracy of the digital examination was examined in relation to maternal and fetal characteristics.

RESULTS

Digital examination failed to define the correct fetal head position in 17 (26.6%) cases. In 12 of 17 (70.6%) errors the difference was >/= 90 degrees and in five (29.4%) the difference was between 45 degrees and 90 degrees. The accuracy of vaginal digital examination was 83% for occiput-anterior and 54% for occiput-lateral + occiput-posterior positions. Logistic regression analysis demonstrated significant independent contributions in explaining the variance in the accuracy of vaginal examination for the station of the fetal head, the position of the fetal head and the experience of the examining obstetrician.

CONCLUSIONS

Digital examination during instrumental delivery fails to identify the correct fetal head position in about one quarter of cases.

Controversies in the use of the vacuum extractor

Operative pelvic delivery is an important component of obstetrical care. Vacuum extraction assumes a prominent role, and when appropriately performed, has been proven safe and effective. However, controversies continue to exist. Historical background and review of the latest literature are presented to delineate these issues and promote consensus and direct research to continue to provide the safest means of delivery for the mother and baby.

Anatomy and physiology of the female perineal body with relevance to obstetrical injury and repair

The female perineal body is a mass of interlocking muscular, fascial, and fibrous components lying between the vagina and anorectum. The perineal body is also an integral attachment point for components of the urinary and fecal continence mechanisms, which are commonly damaged during vaginal childbirth. Repair of injuries to the perineal body caused by spontaneous tears or episiotomy are topics too often neglected in medical education. This review presents the anatomy and physiology of the female perineal body, as well as clinical considerations for pelvic reconstructive surgery.

An evaluation by focus group and survey of a course for Midwifery Ventouse Practitioners

OBJECTIVE

to evaluate the Midwifery Ventouse Practitioners' (MVPs) Course and the MVPs' perception of its effect on their practice.

DESIGN

qualitative and quantitative.

PARTICIPANTS

18 midwives who had completed the MVP course at Bournemouth University 1998-2000.

DATA COLLECTION

focus group (n=8) and postal questionnaire (n=18).

FINDINGS

important issues were identified by the focus group and informed the development of the questionnaire which achieved a 100% response rate. The mean length of full-time experience as a midwife was 18.6 years (SD 6.8; range 9-33); 11 midwives were based in community maternity units and seven in consultant units. Seventeen of the MVPs had been called to assist 505 women in this capacity; 366 (72%) had an MVP ventouse-assisted birth, 129 (26%) a normal birth and 10 women (2%) needed obstetric assistance. In this regard, there were considerable differences between individual MVPs. The midwives gave high priority to woman-centred values and to the very judicious use of intervention. They felt that the course had increased their confidence in relation to their midwifery practice, in general, and their ability to define fetal position and station, in particular. They reported a high level of confidence when undertaking their first ventouse birth after completing the course.

KEY CONCLUSIONS AND IMPLICATIONS

midwives who have undertaken this course do not appear to expand their role to the detriment of normal midwifery, as had been feared. Even highly experienced midwives value increasing their confidence in relation to vaginal and abdominal examination. Ambulance transfer in the second stage of labour was prevented for at least 109 women. A long-term clinical evaluation of the births to which an MVP has been called is needed.

Vacuum-assisted delivery

Unsuccessful vacuum extraction, cup detachment and failed anterior rotation in occipitoposterior positions are commonly associated with obstetric factors that are avoidable or correctable. These factors include the preferential use of soft vacuum cups, incorrect cup applications and attempts to deliver with the vacuum extractor before the cervix is completely dilated. Evidence from randomized trials demonstrates that soft cups cause fewer cosmetic effects and scalp lacerations than rigid cups. Soft cups do not reduce the incidence of cephalhaematomas nor have they been shown to provide any advantage over rigid cups for the prevention of subgaleal haemorrhage. Clinically significant subgaleal haemorrhage and intracranial injury are almost always preceded by difficult vacuum extraction. Although the vacuum extractor is less likely than forceps to injure the mother's genital tract and anal sphincters at delivery, no significant differences have been demonstrated between the instruments in terms of subsequent urinary or bowel disturbances.

The case against elective cesarean section

Prominent American and British obstetricians have been advocating for performing more Cesareans. They argue that Cesarean section is as safe or nearly as safe as vaginal birth, eliminates pelvic floor damage and the consequent symptoms caused by vaginal birth, is safer for the infant, and is desired by many women; however, abundant evidence in the medical literature refutes the validity of those claims.

Obstetric vacuum extraction: state of the art in the new millennium

This article summarizes the current state of knowledge of obstetric vacuum extraction. The discussed topics include the history of vacuum extraction, indications and contraindications, technique of the procedure, currently marketed instruments, special uses of the vacuum extractor, comparison of vacuum extraction with forceps delivery, and maternal and fetal outcomes. Areas of controversy are identified and discussed. Vacuum extraction is replacing forceps as the preferred method of instrumental delivery.

The effect of sequential use of vacuum and forceps for assisted vaginal delivery on neonatal and maternal outcomes

OBJECTIVE

To determine the risk of neonatal and maternal disease associated with the sequential use of vacuum and forceps compared with spontaneous vaginal delivery.

STUDY DESIGN

Using Washington state birth certificate data linked to hospital discharge records, we compared 3741 vaginal deliveries by both vacuum and forceps, 3741 vacuum deliveries, and 3741 forceps deliveries to 11,223 spontaneous vaginal deliveries.

RESULTS

Compared with spontaneous vaginal deliveries, deliveries by sequential use of vacuum and forceps had significantly higher rates of intracranial hemorrhage (relative risk [RR], 3.9; 95% confidence interval [CI], 1.5 to 10.1), brachial plexus (RR, 3.2; 95% CI, 1.6 to 6.4), facial nerve injury (RR, 13.3; 95% CI, 4.7 to 37.7), seizure (RR, 13.7; 95% CI, 2.1 to 88.0), depressed 5-minute Apgar score (RR, 3.0; 95% CI, 2.2 to 4.0), assisted ventilation (RR, 4.8; 95% CI, 2.1 to 11.0), fourth-degree (RR, 11.4; 95% CI, 6.4 to 20.1 among multiparous women) and other lacerations, hematoma (RR, 6.2; 95% CI, 2.1 to 18.1 among multiparous women), and postpartum hemorrhage (RR, 1.6; 95% CI, 1.3 to 2.0). The relative risk of sequential vacuum and forceps use was greater than the sum of the individual relative risks of each instrument for intracranial hemorrhage, facial nerve injury, seizure, hematoma, and perineal and vaginal lacerations.

CONCLUSION

Sequential use of vacuum and forceps is associated with increased risk of both neonatal and maternal injury.

[Obstetrical vacuum: a modern instrument]

Contrary to the forceps, the vacuum extractor has clearly progressed in the last years. The use of the vacuum extractor increases in every developed countries, certainly because of an easier learning than forceps. Furthermore, maternal after-effects of the delivery like sphincters injuries and anal incontinence seem to be less frequent with vacuum extractor than with forceps. For these reasons the American College of Gynecologists and Obstetricians (ACOG) recommend a large use and a priority teaching of this fetal extraction instrument. The technical aspects of use of the vacuum extractor are developed in this article, and personnel results are added as commentaries.

Anal sphincter injury after vaginal delivery in primiparous females

PURPOSE

The purpose of this study was to determine the incidence of anal sphincter injury and fecal incontinence after vaginal delivery.

METHODS

This was a prospective, descriptive, observational study conducted over a three-year period in healthy primiparous females with previously intact anal sphincter and normal continence and without history of anorectal surgery. All patients completed a continence questionnaire and underwent endoanal ultrasound four to six weeks before and six weeks after delivery.

RESULTS

Ninety-eight primiparous females had either instrumental (vacuum or forceps) vaginal delivery (n = 23) or noninstrumental vaginal delivery (n = 75). Twenty patients, 11 (48 percent) after instrumental delivery and 9 (12 percent) after noninstrumental vaginal delivery, had clinical sphincter tears that required primary repair. Twenty-eight patients (29 percent), 19 with previously repaired sphincter injury, had ultrasonographic defects that involved the external sphincter (n = 19) or both the internal and external sphincter (n = 9). Twenty-one patients (75 percent) with ultrasonographic sphincter defects had either major (n = 5) or minor (n = 16) fecal incontinence.

CONCLUSION

Anal sphincter injuries, many of them undiagnosed at the time of delivery, are common in primiparous females after vaginal delivery, especially if vacuum or forceps are used. These injuries cause fecal incontinence in a significant proportion of the patients. Patients undergoing vaginal delivery should be aware of the risks of anal sphincter injury.

Characteristics and outcome of deliveries by forceps after failed ventouse

With the increasing use of the ventouse, it is becoming common for deliveries to be completed by the application of forceps. We present 48 cases delivered by forceps after a failed ventouse and compare these with 63 cases delivered by forceps only. There was significantly higher incidence of caesarean sections and cephalhaematoma in the group where forceps delivery was attempted after a failed ventouse compared to those delivered with forceps only.

A random controlled trial of two different vacuum extractor pumps: new foot pump and electric pump

Worldwide the vacuum extractor is the instrument used most commonly for assisted vaginal delivery. Many institutions use electric pumps in preference to the original hand pump, considered by some to be inefficient (requiring an assistant). A new foot pump has been developed. In a controlled comparison with a standard electric pump, no differences in efficiency were found.

Anal function: effect of pregnancy and delivery

OBJECTIVE

To investigate the effect of pregnancy and delivery on anal continence, sensation, manometry, and sphincter integrity.

STUDY DESIGN

Two hundred eighty-six nulliparous women in the third trimester completed a symptom questionnaire and underwent anorectal sensation and manometric evaluations. Three months postpartum, 161 women returned and the questionnaires and investigations were repeated together with anal endosonographic examinations.

RESULTS

The prevalence of fecal urgency before, during, and after pregnancy was 1%, 9.4%, and 10.5%, respectively; the prevalence of anal incontinence before, during, and after pregnancy was 1.4%, 7.0%, and 8.7%, respectively. Vaginal delivery, particularly instrumental, resulted in a decrease in anal squeeze pressures (P =.015) and resting pressures (P =.002) but had no effect on anal sensation. Postpartum anal endosonographic examination revealed sphincter disruption in 38% of women. There was no relationship between symptoms and anal manometry, sensation, or sphincter integrity. Vaginal delivery (P <.0001) and perineal trauma (P <.001) were significantly associated with sphincter defects.

CONCLUSION

Vaginal delivery is associated with a decrease in anal pressures and increased anal sphincter trauma but has no effect on anal sensation. These changes were not related to anal symptoms.

Delivery method and self-reported postpartum general health status among primiparous women

Despite nearly four million deliveries in the United States each year, minimal information exists on unintended health consequences following childbirth, particularly in relation to delivery method. The purpose of this study was to assess the association between method of delivery and the general health status, sexual, bowel and urinary functioning of primiparous women as measured at 7 weeks postpartum. Data from the Statewide Obstetrical Review of Quality System (StORQS) Survey of Maternity Care in Washington State were analysed. Participants included all primiparous women with a delivery of a singleton infant discharged alive between August and December 1991 from 10 non-federal short-stay hospitals who responded to the StORQS Survey of Maternity Care (n = 971). The main outcome measures included the modified Medical Outcomes Study 36-Item Short-Form Health Survey and self-reported sexual, bowel and urinary functioning. At 7 weeks postpartum, women who had caesarean or assisted vaginal deliveries reported significantly lower postpartum general health status scores than women with unassisted vaginal delivery. Additionally, women with assisted vaginal delivery reported significantly worse sexual, bowel and urinary functioning. Our results suggest that more careful attention to the postpartum general health and sexual functioning of women with caesarean and assisted vaginal delivery may be merited.

Obstetric practice and faecal incontinence three months after delivery

OBJECTIVE

To determine whether obstetric and maternal factors relate to faecal incontinence at three months postpartum.

SETTING

Maternity units in Aberdeen (Scotland), Birmingham (England) and Dunedin (New Zealand).

POPULATION

All women who delivered during one year in the three maternity units.

METHODS

Postal questionnaire at three months postpartum, to obtain information on faecal incontinence, linked to obstetric casenote data.

MAIN OUTCOME MEASURES

Prevalence of faecal incontinence.

RESULTS

7879 questionnaires were returned, a 71.7% response rate. The prevalence of faecal incontinence was 9.6%, with 4.2% reporting this more often than rarely. Logistic regression, confined to primiparae, showed that forceps delivery was a predictor of an increased risk of symptoms (OR = 1.94, 95% CI 1.30 to 2.89) while vacuum extraction was not associated. Caesarean section was marginally associated with a reduced risk (OR = 0.58, 95% CI 0.35 to 0.97). Older maternal age, Indian sub-continent ethnic origin and body mass index 'not known' also showed significant associations. No associations were found for induced labour, duration of second stage labour, episiotomy, laceration or birthweight.

CONCLUSIONS

Women delivered by forceps had almost twice the risk of developing faecal incontinence, whereas vacuum extraction was not associated with faecal incontinence at three months postpartum. Caesarean section appears to offer some protection.

Trends in operative vaginal delivery rates and associated maternal complication rates in an inner-city hospital

OBJECTIVE

The aims of this study were to determine trends in operative vaginal delivery rates in a large inner-city hospital and to assess associated risks.

STUDY DESIGN

We performed a retrospective cohort study (1980-1996) of women with singleton term pregnancies who underwent operative vaginal delivery at Grady Memorial Hospital, Atlanta. Maternal complication rates were compared between forceps-assisted and vacuum-assisted methods.

RESULTS

There was a decline in forceps-assisted deliveries during the 1980s and an increase during the 1990s. The vacuum-assisted delivery rate was exceedingly low during the 1980s and increased during the 1990s. Women who underwent forceps-assisted delivery were more likely to be <24 years old, to be nulliparous, and to have had regional anesthesia, midline episiotomies, and infant presentations other than occipitoanterior (P <.001). Women who underwent forceps-assisted deliveries had increased risks of postpartum infection, cervical laceration, prolonged hospital stay, perineal laceration, and postpartum complications.

CONCLUSION

There were upward trends in the rates of operative vaginal delivery at this inner-city hospital. Women who underwent forceps-assisted delivery had greater rates of maternal complications than did those who underwent vacuum-assisted delivery.

Obstetric complications in women with schizophrenia

It is not known whether schizophrenic women have increased incidence of complications during pregnancy and delivery. Data from the Danish Medical Birth Register were used to compare 2212 births to 1537 schizophrenic women in Denmark with a random sample of all deliveries in Denmark during 1973-1993 (122931 births to 72742 women). The schizophrenic women had fewer antenatal care visits. They were at lower risk of pre-eclampsia, but tended to have lower Apgar scores. There were no other differences in the incidence of specific complications such as placenta previa, placental abruption, and abnormal fetal presentation. Schizophrenic women were at increased risk of interventions such as Cesarean section, vaginal assisted delivery, amniotomy, and pharmacological stimulation of labor. There were no important differences between the deliveries to schizophrenic women who gave birth before and after their first admission to a psychiatric department. These results show no evidence that schizophrenic women have a greater frequency of specific obstetric complications than non-schizophrenic women. Nevertheless, they are at increased risk for interventions during delivery.

Comparison of maternal and infant outcomes between vacuum extraction and forceps deliveries

The authors conducted a population-based historical cohort study in the Canadian province of Quebec to assess the maternal and infant outcomes associated with vacuum extraction and forceps deliveries. The study database contains information on 305,391 mother-infant dyads (linked by a common institutional code and hospital chart number) for singleton live vaginal births with a nonbreech presentation at the gestational age of 37 or more completed weeks and a birth weight between 2,500 and 4,000 g during fiscal years 1991/1992 to 1995/1996. Of the births, 31,015 were delivered by vacuum extraction, and 18,727 were delivered by forceps. Compared with delivery by forceps, the adjusted risk ratios for third-/fourth-degree perineal laceration, intracranial hemorrhage, subdural or cerebral hemorrhage, intraventricular hemorrhage, subarachnoid hemorrhage, cephalhematoma, and neonatal in-hospital death were 0.48 (95% confidence interval: 0.45, 0.50), 1.28 (95% confidence interval: 0.73, 2.25), 0.97 (95% confidence interval: 0.49, 1.93), 0.99 (95% confidence interval: 0.16, 5.97), 5.44 (confidence interval: 1.26, 23.43), 2.02 (95% confidence interval: 1.89, 2.16), and 0.93 (95% confidence interval: 0.32, 2.70), respectively. The authors conclude that vacuum extraction causes less maternal trauma but may increase the risk of cephalhematoma and certain types of intracranial hemorrhage (e.g., subarachnoid hemorrhage).

Birth trauma: short and long term effects of forceps delivery compared with spontaneous delivery on various pelvic floor parameters

OBJECTIVE

To compare the effects of forceps delivery and spontaneous delivery on pelvic floor functions in nulliparous women.

DESIGN

A longitudinal prospective study with investigations during the first pregnancy, 10 weeks and 10 months after delivery.

SETTING

Antenatal clinic in a teaching hospital.

POPULATION

One hundred and seven patients aged 28 +/- 4 years, divided into those with forceps (n = 25) or spontaneous (n = 82) delivery.

METHODS

Investigations with a questionnaire, clinical examination, assessment of bladder neck behaviour, urethral sphincter function, intra-vaginal/intra-anal pressures during pelvic floor contractions.

RESULTS

The incidence of stress urinary incontinence was similar in both groups at 9 weeks (32% vs 21%, P = 0.3) and 10 months (20% vs 15%, P = 0.6) after delivery, as was the incidence of faecal incontinence (9 weeks: 8% vs 4%, P = 0.9; 10 months: 4% vs 5%, P = 1) and the decreased sexual response at 10 months (12% vs 18%, P = 0.6). Bladder neck behaviour, urethral sphincter function and intra-vaginal and intra-anal pressures were also similar in the two groups. However, 10 months after delivery, the incidence of a weak pelvic floor (20% vs 6%, P = 0.05) and the decrease in intra-anal pressure between the pre- and post-delivery values (-17 +/- 28 cm H2O vs 3 +/- 31 cm H2O, P = 0.04) were significantly greater in the forceps-delivered women.

CONCLUSIONS

Forceps delivery is not responsible for a higher incidence of pelvic floor complaints or greater changes in bladder neck behaviour or urethral sphincter functions. However, patients with forceps delivery have a significantly greater decrease in intra-anal pressure and a greater incidence of a weak pelvic floor.

Impact of FDA advisory on reported vacuum-assisted delivery and morbidity

OBJECTIVE

In May 1998 the US Food and Drug Administration (FDA) issued a health advisory reporting neonatal injuries/deaths following vacuum delivery and encouraged voluntary reports of future adverse events. We compared FDA reports of vacuum delivery adverse events prior to and following the advisory.

METHODS

The FDA database (MAUDE) was searched for vacuum deliveries using brand name, manufacturer name, and procedure "string searches." Cases were sorted by report date, source, and manufacturer. Neonatal morbidity was quantified as deaths and life-threatening or nonlife-threatening events.

RESULTS

A total of 80 reported adverse cases were identified after duplicate cases were consolidated. Twenty-five were reported to the FDA prior to the 1998 advisory and 55 in the immediate 6-month period following the advisory. There was a 22-fold increase in reported events from five events/year prior to the advisory to an estimated 110 events/year following the advisory. The distribution of reporting sources changed significantly following the advisory with increased "manufacturer" (8-43%) and decreased "voluntary" reports (56-20%). All major brand names were represented. During the 6 months following the FDA advisory there were 10 neonatal deaths, 30 life-threatening events, 12 nonlife-threatening events, and three equipment-related reports. Infant deaths were due to intracranial or subgaleal hematomas. Injuries included skull fracture, scalp abrasions, and cephalohematomas.

CONCLUSIONS

The FDA advisory was associated with a 22-fold increase in the rate of reported adverse events. This increase in reporting likely represents both enhanced awareness of complications as well as an increase in vacuum-related adverse neonatal sequelae. As vacuum delivery is associated with greater neonatal morbidity/ mortality than was previously recognized, the adage that the vacuum is "designed to come off before infant damage occurs" appears unsubstantiated. It is recommended that manufacturers quantify the suction and traction capabilities of present and new proposed vacuum cup designs.

Anal sphincter tears: prospective study of obstetric risk factors

OBJECTIVE

To evaluate intrapartum risk factors for anal sphincter tear.

DESIGN

A prospective observational study.

SETTING

Delivery unit at the University Hospital in Göteborg, Sweden.

PARTICIPANTS

2883 consecutive women delivered vaginally during the period between 1995 and 1997. Information was obtained, from patient records and from especially designed protocols which were completed during and after childbirth.

MAIN OUTCOME MEASURES

Anal sphincter (third and fourth degree) tear.

RESULTS

Anal sphincter tear occurred in 95 of 2883 women (3.3%). Univariate analysis demonstrated that the risk of anal sphincter tear was increased by nulliparity, high infant weight, lack of manual perineal protection, deficient visualisation of perineum, severe perineal oedema, long duration of delivery and especially protracted second phase and bear down, use of oxytocin, episiotomy, vacuum extraction and epidural anaesthesia. After analysis with stepwise logistic regression, reported as odds ratio, 95% confidence interval, the following factors remained independently associated with anal sphincter tear: slight perineal oedema (0.40, 0.26-0.64); manual perineal protection (0.49, 0.28-0.86); short duration of bear down (0.47, 0.24-0.91); no visualisation of perineum (2.77, 1.36-5.63); parity (0.59, 0.40-0.89); and high infant weight (2.02, 1.30-3.16). Analysis of variance showed that manual perineal protection had a stronger influence on lowering the frequency, and lack of visualisation of perineum and infant weight had a stronger influence on raising the frequency, of anal sphincter tears in nulliparous compared with parous women.

CONCLUSIONS

Perineal oedema, poor ocular surveillance of perineum, deficient perineal protection during delivery, protracted final phase of the second stage, parity and high infant weight all constitute independent risk factors for anal sphincter tear. Such information is essential in order to reduce perineal trauma during childbirth.