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.

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

OBJECTIVES: The association between the use of forceps and levator ani muscle (LAM) avulsion seems to be clear-cut. However, whether the lesion is due to the mechanical trauma yielded by the instrument or to the intrinsic complexity of this type of delivery, is yet to be determined. This study aims at determining the difference in LAM avulsion rate between Kielland rotational forceps and non-rotational forceps. STUDY DESIGN: Prospective observational study with 94 nulliparous women with forceps-assisted deliveries (FD) between July 2015 and January 2016. 3D-TpUS was performed 6 months after every patient's delivery, during which LAM avulsion, and levator hiatus area and anteroposterior and transverse diameters were assessed. RESULTS: A total of 89 nulliparous were studied, comprising 27 rotational-FD, and 62 non-rotational-FD. No differences in obstetric, intrapartum, or neonatal characteristics were observed between study groups. There were no statistically significant differences in the presence of avulsion between cases of rotational forceps (44.4% vs 35.5%, OR: 1.5 [0.6-3.6]), correction of asinclitism of the fetal head (34.4% vs. 40.4% OR: 0.8 [0.3-1.9]) or station (midforceps: 32.8% vs low forceps: 50.0% OR: 2.0 [0.8-5.1]). CONCLUSIONS: We have not observed differences in the LAM-avulsion rate between rotational forceps and non-rotational forceps performed by highly experienced personnel in instrumental deliveries.

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

OBJECTIVES: Evaluation of the influence of difficulty of instrumentation with vacuum on the rate of levator ani muscle (LAM) avulsions. MATERIALS AND METHODS: Prospective observational study with 86 nulliparous women with at term gestation who required instrumentation with vacuum to complete fetal extraction. After every delivery, each explorer reported the number of vacuum tractions needed to complete fetal extraction, as well as the subjective complexity of the instrumentation. LAM avulsion rate was assessed by 3D-4D transperineal ultrasound evaluation 6 months after delivery. RESULTS: Seventy nine cases were evaluated and classified as either "easy" delivery (below three vacuum tractions; n = 49) or "difficult" delivery (three or more vacuum tractions; n = 30). No differences in obstetric characteristics were observed between study groups, with the following exceptions: fetal head circumference (34.8 ± 2.7 versus 35.2 ± 1.1; p = .013) and fetal weight at birth (3260 ± 421 versus 3500 ± 421; p = .016). No statistically significant differences between study groups were observed in LAM avulsion rate (36.7 versus 30%) and levator hiatus area (cm2) at rest (18.44 ± 3.95 versus 17.75 ± 3.90). CONCLUSIONS: The number of vacuum tractions needed to complete fetal extraction is not associated to a higher LAM avulsion rate nor with differences in levator hiatus area.

Evaluation of levator ani muscle throughout the different stages of labor by transperineal 3D ultrasound.

OBJECTIVE: Description and assessment by 3-D transperineal ultrasound of modifications suffered by pelvic floor muscles during the passage of the fetal head through the birth canal during the second stage of labor, as well as the identification of the precise moment in which levator ani muscle avulsion takes place. MATERIALS AND METHODS: Patients included were 35 primigravidae, recruited during the first stage of labor, with at term pregnancy (37-42 weeks), without serious maternal-fetal pathology and cephalic presentation. A prospective observational study of 35 primigravidae, recruited during the first stage of labor, with at term pregnancy (37-42 weeks), with fetus in cephalic presentation and without serious maternal-fetal pathology. Sonographic evaluation was carried out by 3-D transperineal ultrasound during the first and second stages of labor (with fetal head in 1st, 2nd-3rd and 4th planes of Hodge), immediately postpartum and 6 months postpartum. Ultrasound parameters studied were antero-posterior and transverse diameters, as well as levator hiatus area and levator ani muscle thickness and area. RESULTS: Twenty-one patients were studied (15 spontaneous deliveries; 6 instrumental deliveries). When measured with fetal head in the 4th plane of Hodge, a significant increase both in the levator hiatus area (15.39 cm2 /15.68 cm2 /20.96 cm2 /42.55 cm2 /22.92 cm2 /18.18 cm2 ; P < 0.0005) and in the levator ani muscle area (8.78 cm2 /9.18 cm2 /9.69 cm2 /15.07 cm2 /11.33 cm2 /12.36 cm2 ; P < 0.0005) was identified. Four cases of unilateral right avulsion (two vacuum and two forceps deliveries) were identified. CONCLUSIONS: We conclude that the phase of delivery that causes a major increase in the area of the levator hiatus area and in the levator ani muscle area is when the fetal head reaches the 4th plane of Hodge. Furthermore, data in our paper indicates that the exact moment in which the avulsion of the levator ani muscle is produced is when the bulging of the fetal head on the maternal perineum occurs.