The correlation between the type of forceps application and the rate of levator ani muscle avulsion: A prospective cohort study

Incidence of obstetric anal sphincter injuries according to the type of forceps used in the Mexican population

OBJECTIVE

This study describes the frequency of obstetric anal sphincter injuries (OASIS) in patients after instrumental delivery according to the type of forceps used.

METHODS

A retrospective comparative cohort study was conducted on patients who underwent instrumental delivery from January 2017 to April 2022. The primary outcome was the presence of OASIS following delivery. Patients were categorized into Cohort A if only rotation forceps were used, Cohort B for only traction forceps, and Cohort C if both types were used sequentially. Statistical analysis was performed with SPSS (IBM, New York, NY) with χ2, Fisher's exact, and analysis of variance testing. A P-value <0.05 was considered significant.

RESULTS

OASIS occurred in 45 of 328 instrumental deliveries. OASIS after rotation forceps occurred in 12.9% (n = 8) of cases, after traction forceps in 13.2% (n = 34), and after sequential use of rotation and traction forceps in 37.5% (n = 3) of cases (p = 0.141). An odds ratio (OR) of 0.91 (95% confidence interval [CI] 0.40-2.08) for OASIS was obtained with the use of rotation forceps, 0.81 (95% CI 0.38-1.70) for traction forceps, and 3.97 (95% CI 0.91-17.2) for the sequential use of rotation and traction forceps.

CONCLUSION

There were no significant differences in the presence of OASIS comparing traction and rotation forceps. A non-significant trend of higher OASIS following the sequential use of traction and rotation forceps was observed.

Has the prevalence of levator avulsion after forceps delivery changed over the last six decades? A retrospective study in a urogynaecological population

OBJECTIVE

Forceps delivery is associated with a higher risk of maternal birth trauma. It is speculated that it is due to sub-optimal use of forceps in inexperienced hands. The aim of this study was to determine the association between time of forceps birth and prevalence of levator avulsion over the last six decades.

STUDY DESIGN

This was a retrospective analysis of datasets of women with a history of forceps delivery, seen at a tertiary urogynaecological centre between January 2014 and August 2018. They had undergone a standardized interview, clinical examination and four-dimensional translabial ultrasound. Archived imaging data was reviewed for levator avulsion offline at a later date, blinded against all clinical data. Associations between levator avulsion, maternal age at first vaginal birth, the weight of the first vaginally born baby, and time since forceps delivery categorised by decade were tested by univariable analysis. Factors found to be significant on univariable analysis were included in a multivariable logistic regression model to test the association between prevalence of levator avulsion and time of forceps delivery while controlling for confounders.

RESULTS

In total, 2026 patients were seen during the study period. Among them 511 (25.2%) had a history of forceps delivery. Fourteen volume datasets were incomplete or missing, leaving 497 complete datasets for analysis. Mean age at presentation was 58 ± 12 years (23-91). Mean body mass index was 29 ± 6 kg/m². Mean age at first delivery was 25 ± 5 years. Mean birth weight of the first vaginal birth was 3454 ± 557 g. 457 women (92%) had had one forceps delivery, 31 had two forceps deliveries (6%) and 9 had three forceps deliveries (2%). Mean time interval between forceps delivery and assessment was 32 ± 13 years (0.3-64.8). 229 women (46%) were diagnosed with levator avulsion. The prevalence of avulsion after forceps increased significantly from 34% to 56% between 1950 and 2017 (P = 0.04). However this difference became insignificant when controlling for maternal age at 1st vaginal delivery and birth weight.

CONCLUSIONS

We found no evidence of a changed prevalence of levator avulsion at forceps delivery over the last 67 years.

Adding Insult to Injury: Levator Ani Avulsion in Women With Obstetric Anal Sphincter Injuries

OBJECTIVE

In women with obstetric anal sphincter injuries, we compared the rate of major levator ani avulsion after forceps-assisted delivery versus spontaneous vaginal delivery.

METHODS

Prospective cohort of primiparous women with obstetric anal sphincter injuries. The primary outcome was the rate of major levator ani avulsion as measured by 3-dimensional transvaginal ultrasonography performed between 1 and 2 weeks postpartum. Secondary outcomes included ultrasonographic anteroposterior hiatal diameter, levator hiatal area, and levator-urethra gap, and differences in validated pelvic disorder questionnaires scores at 1 to 2 and 13 weeks postpartum.

RESULTS

Sixty-two women (30 spontaneous deliveries, 32 forceps deliveries) were included in the final analysis. After controlling for delivery variables, women who underwent forceps-assisted delivery were more likely to experience a major avulsion as compared with those who underwent spontaneous delivery (21/32, [65.6%] vs 8/30 [26.7%]; odds ratio, 5.9; 95% confidence interval, 1.5-24.5; P = 0.014). They were also more likely to have larger levator-urethra gaps bilaterally (P = 0.012, 0.016). After controlling for potential confounders, levator ani avulsion was independently associated with persistent anal incontinence symptoms at 13 weeks postpartum (P = 0.02).

CONCLUSIONS

In women with obstetric anal sphincter injuries, the risk of levator ani avulsion is almost 6 times higher after forceps-assisted vaginal delivery as compared with spontaneous vaginal delivery. In those with avulsion, recovery of anal continence is compromised, suggesting that adding insult (avulsion) to injury (obstetric anal sphincter injury) may have negative functional consequences.

Rotational forceps: a retrospective study evaluating anatomical and functional consequences for the pelvic floor

INTRODUCTION AND HYPOTHESIS

The use of Kielland's rotational forceps is considered to involve greater technical difficulty and may be associated with a higher rate of pelvic floor trauma. Our main objective was to evaluate the association between avulsion of the levator muscle and rotational and non-rotational forceps.

METHODS

This was an observational study carried out at a tertiary hospital that recruited singleton cephalic vaginally primiparous women with previous Kielland's forceps delivery between March 2012 and May 2017. Patients were retrieved from a local database, contacted consecutively and blinded to all clinical data. Power calculations determined a sample of n = 160 patients. All women underwent a urogynecological interview, clinical examination and 4D translabial ultrasound (TLUS). The 4D TLUS volumes were stored and analyzed offline by an experienced ultrasound examiner who was blinded to all clinical data.

RESULTS

A total of 165 patients were available for analysis. Rotational forceps accounted for 27.3% (45 out of 165) of the study sample. Avulsion was present in 41.8% (69 out of 165) of all forceps deliveries. On multivariate analysis, rotational forceps was associated with avulsion, with an adjusted odds ratio (OR) of 2.57 (CI 95% 1.20-5.62, p = 0.016). Body mass index at the beginning of gestation was found to be a protective factor, with an adjusted OR of 0.918 (CI 95% 0.847-0.986, p = 0.025).

CONCLUSION

Rotational forceps is associated with a higher avulsion rate than non-rotational forceps, with an adjusted OR of over 2.5. Obstetricians need to consider the potential long-term consequences of performing a rotational forceps for mothers.

Prevalence of levator ani avulsion in a multicenter study (PAMELA study)

PURPOSE

The objective is to determine the prevalence of levator ani muscle (LAM) avulsion using four-dimensional ultrasound in primiparous women after vaginal delivery and according to delivery mode.

METHODS

This prospective, multicenter study included 322 women evaluated at 6-12 months postpartum by four-dimensional transperineal ultrasound to identify levator ani muscle avulsion. The researcher who performed the ultrasound was blinded to all clinical data. Meaningful data about the birth were also recorded: mode of delivery, mother's age and body mass index, duration of second stage, episiotomy, perineal tearing, anesthesia, assistant, head circumference and fetal weight.

RESULTS

303 volumes were valid for evaluation. The overall prevalence of levator ani muscle avulsion was 18.8% (95% CI 14.4-23.2%). In our multivariate analysis, only mode of delivery reached statistical significance as a risk factor for levator ani muscle avulsion (p < 0.001). The prevalence according to the different modes of delivery was 7.8% in spontaneous delivery, 28.8% in vacuum-assisted and 51.1% in forceps-assisted delivery. Compared with spontaneous delivery, the OR for LAM avulsion was 12.31 with forceps (CI 95% 5.65-26.80) and 4.78 with vacuum-assisted delivery (CI 95% 2.15-10.63).

CONCLUSIONS

Levator ani avulsion during vaginal delivery in primiparous women occurs in nearly one in every five deliveries. Delivery mode is a significant and modifiable intrapartum risk factor for this lesion. The incidence is lower in spontaneous delivery and significantly increases when an instrument is used to assist delivery, especially forceps.

Influence of the disengagement of the forceps on levator ani muscle injuries in instrumental delivery: A multicenter study

INTRODUCTION

Forceps use is the main risk factor for levator ani muscle (LAM) injuries. We believe that the disengagement of the forceps branches before delivery of the fetal head could influence LAM injuries, so we aimed to determine the influence of the disengagement of the forceps on the occurrence of LAM avulsion during forceps delivery.

MATERIAL AND METHODS

A prospective, observational, multicenter study was conducted with 261 women who underwent forceps delivery. The women were classified according to whether the branches of the forceps had been disengaged before delivery of the fetal head. LAM avulsion was defined using a multislice mode (3 central slices).

RESULTS

In all, 255 women completed the study (160 without disengagement and 95 with disengagement). LAM avulsions were observed in 37.9% of women in the group with disengagement and in 41.9% of women in the group without disengagement. The crude OR (without disengagement vs with disengagement) for avulsion was 0.90 (95% CI 0.49-1.67, P = 0.757) and an adjusted OR of 0.82 (95% CI 0.40-1.69, P = 0.603).

CONCLUSIONS

We did not observe a statistically significant reduction in the LAM avulsion rate with disengagement of the forceps branches before delivery of the fetal head.