Influence of difficulty of instrumentation with vacuum on the rate of levator ani muscle avulsion identified by 3–4 d transperineal ultrasound

Association between the side of levator Ani muscle trauma and fetal position at birth - a prospective observational study

INTRODUCTION

Trauma of the levator ani muscle (LAM) is common after vaginal birth and can most reliably be diagnosed by 3-dimensional (3D) translabial ultrasound (TLUS). Multiple risk factors are known in general, but not in association to a specific side of the body. Therefore, our aim was to evaluate different impact factors which cause LAM trauma on either side of the body or bilateral by focusing on the fetal position at birth.

MATERIAL AND METHODS

As part of a prospective cohort study between 3/2017 and 4/2019, we analyzed vaginal births of nulliparous women with singletons in vertex presentation≥36+0 gestational weeks. We evaluated their pelvic floor for hematomas, partial and complete LAM avulsions by 3D TLUS 2-4 days postpartum and searched for an association between the affected body side and different fetal, maternal and obstetrical factors.

RESULTS

71 out of 213 women (33.3%) suffered from LAM trauma - 17 (23.9%) on the right side, 20 (28.2%) on the left side and 34 (47.9%) bilateral. No association between the different evaluated factors and the affected body side could be identified, except for the quality of fetal heart rate tracing.

CONCLUSIONS

No significant impact factors of LAM trauma could be associated with a specific side of the body. Other possible mechanisms need investigation in the future, such as the time of the birth canal and the fetus to adapt to each other, including adequate time for the tissue to stretch and the fetus to rotate into the ideal position within the LAM hiatus.

EINLEITUNG

Levatormuskelverletzungen sind häufig nach Vaginalgeburten und können zuverlässig mittels translabialem 3D-Ultraschall diagnostiziert werden. Diverse Risikofaktoren sind hierfür bekannt, allerdings keine hinsichtlich der Assoziation zu einer der beiden Körperseiten. Daher war das Ziel dieser Arbeit, verschiedene Einflussfaktoren im Rahmen vaginaler Geburten zu evaluieren, welche eine Levatorverletzung auf einer der beiden Körperseiten bzw. beidseitig begünstigen, v. a. hinsichtlich der Kindsposition im Geburtskanal.

MATERIAL UND METHODIK

In einer prospektiven Kohortenstudie analysierten wir von 3/2017-4/2019 Erstgebärende mit vaginalen Einlingsgeburten aus Schädellage≥36+0 SSW. Wir evaluierten 2-4 Tage postpartal ihren Beckenboden mittels 3D-Ultraschall hinsichtlich Hämatomen sowie partiellen und kompletten Levatoravulsionen und suchten nach Assoziationen zwischen der betroffenen Körperseite und fetalen, maternalen und geburtshilflichen Einflussfaktoren.

ERGEBNISSE

Von 213 Frauen erlitten 71 (33.3%) eine Levatorverletzung - 17 (23.9%) rechtsseitig, 20 (28.2%) linksseitig und 34 (47.9%) beidseitig. Es wurden keine Assoziationen zwischen den untersuchten Einflussfaktoren und der betroffenen Körperseite gefunden, bis auf die Qualität der fetalen Herzfrequenz.

DISKUSSION

Es konnten keine signifikanten Einflussfaktoren für das Auftreten einer Levatorverletzung einer spezifischen Körperseite eruiert werden. Daher bedarf es in Zukunft der Untersuchung weiterer Mechanismen, wie der Adaptationsvorgänge von Geburtskanal und Fet und der adäquaten Zeit für das Gewebe zur notwendigen Dehnung, v. a. im Bereich der Levatoröffnung.

A comparable rate of levator ani muscle injury in operative vaginal delivery (forceps and vacuum) according to the characteristics of the instrumentation

INTRODUCTION

Forceps delivery is associated with a high rate of levator ani muscle (LAM) trauma (avulsion) at 35%-65% whereas data on avulsion rates after vacuum delivery vary greatly. Nevertheless, a common characteristic of all previous studies carried out to evaluate the association between instrumental deliveries (forceps and vacuum) and LAM avulsion, is the fact that characteristics of the instrumentation have not been described or evaluated. The objective of this study is to compare the rate of LAM avulsion between forceps and vacuum deliveries according to the characteristics of the instrumentation.

MATERIAL AND METHODS

Prospective, observational study, including 263 nulliparous women, who underwent an instrumental delivery with either Malmström vacuum or Kielland forceps. The characteristics of the instrumentation, position (anterior position and other position) and height of the fetal head at the moment of instrumentation (low instrumentation [vertex at +2 station] and mid-instrumentation [head is involved but leading part above +2 station]) were assessed. Evaluation of LAM avulsion was performed at 6 months postpartum by three-/four-dimensional transperineal ultrasound. Using the multi-view mode, a complete avulsion was diagnosed when the abnormal muscle insertion was identified in all three central slices, that is, in the plane of minimal hiatal dimensions and the 2.5-mm and 5.0-mm slices cranial to this one. To detect a 30% or 15% difference in the LAM injury rate, with 80% power and 5% α-error, we needed, respectively 42 and 99 women per study group.

RESULTS

In all, 263 nulliparous individuals have been evaluated (162 vacuum deliveries, 101 forceps deliveries). Instrumentation in an occipito-anterior position was more frequent in vacuum deliveries (75.3% vs 56.4%, P = .002), whereas other positions were more frequent in the forceps deliveries group (24.7% vs 43.6%). No statistically significant differences were noted regarding the height of the fetal head at the moment of instrumentation. No statistically significant differences were found in the presence of LAM avulsion (41.4% vs 38.6%) between vacuum and forceps deliveries. The univariate analysis of the crude odds ratio was 1.17, 95% CI 0.67-1.98, P = .70 for the avulsion of the LAM and the multivariate of the adjusted OR 0.90, 95% CI; 0.53-1.55, P = .71.

CONCLUSIONS

We consider that, in our population, LAM avulsion rate should not be a factor taken into account when choosing the type of instrumentation (Malmström vacuum or Kielland forceps) in an operative delivery.

Can we predict levator ani muscle avulsion in instrumental deliveries through intrapartum transperineal ultrasound?

Introduction: To determine whether intrapartum translabial ultrasound (ITU) is useful for the prediction of levator ani muscle (LAM) avulsions in instrumental deliveries (vacuum and forceps). Materials and methods: Prospective, observational study, including (1/2016 - 5/2016) 77 nulliparous women, with singleton pregnancies of ≥37 weeks of gestation and with cephalic presentation, who required vacuum or forceps instrumentation to complete the delivery. The ITU parameters evaluated were Angle of Progression (AoP), Progression Distance (PD), Head Direction (HD), and Midline Angle (MLA), both at rest and with maternal push. Evaluation of LAM avulsion was performed at 6 months postpartum with 3-4D transperineal ultrasound. Complete avulsion was defined as an abnormal insertion of LAM in the lower pubic branch identified in all three central slices. Results: Data from 48 nulliparous women were finally included in the study (34 vacuum and 14 forceps). We observed no difference in obstetric parameters between the two study groups (group with avulsion of LAM -14 cases, 29.2% - and group without avulsion of LAM -34 cases, 70.8%). The "LAM avulsion group" had an AoP and a PD of 136.7 ± 22.4 and 43.5 ± 15.6, respectively, versus 141.6 ± 21.3 and 47.2 ± 16.8 recorded in the group without avulsion (NS), respectively. We obtained a ROC curve for AoP and PD with a push of 0.66 (95% CI, 0.28-1.00) and 0.57 (95% CI, 0.39-0.75), respectively. Conclusions: ITU is not a useful technique to predict the occurrence of LAM avulsion in instrumental deliveries with vacuum or forceps.