McRoberts' maneuver increases fetal head angle of progression in second stage of labor.

Abstract

Intrapartum angle of progression (AoP) is the leading sonographic parameter for the assessment of fetal head descent in labor. AoP > 120° in the second stage of labor is correlated with spontaneous vaginal delivery, and AoP > 145.5° with successful vacuum extraction1–3. A comparison between AoP and three other sonographic methods for the assessment of second-stage fetal head descent (head direction, angle of middle line and progression distance) found that AoP had the highest inter- and intraobserver reproducibility4. Using AoP in our delivery ward, we observed inconsistencies in measured AoP in different maternal positions. This raised the question of whether AoP measured in a standard birthing bed, with stirrups, with maternal hip hyperflexion (McRoberts' maneuver) or with maternal hip extension would provide the same result. To assess this clinical observation, we conducted this study. We recruited 50 nulliparous term (over 37 weeks of gestation) patients who were in the second stage of labor (full cervical dilatation) and with a fetus in the occipitoanterior position. Using a goniometer, we measured AoP at four femoropelvic angle (FPA) stations: (1) FPA = −10° (hip extended); (2) FPA = 0° (lying flat); (3) FPA = 45° (knees flexed); and (4) FPA > 135° (McRoberts' maneuver, i.e. hip hyperflexion). Exclusion criteria included multiple pregnancy, non-vertex or non-occipitoanterior fetal position, or a medical condition that prevents maternal hip hyperflexion. Ultrasound examinations were performed between contractions and with no maternal pushing, using a Voluson e portable ultrasound machine (GE Medical Systems, Zipf, Austria). Patients were in the supine position, without stirrups, in a standard birthing bed (Affinity-4, Hill-Rom, IN, USA). The headboard was kept at 30° inclination. The study was approved by our local review board (No. 0303-15-ASF). A satisfactory AoP measurement was obtained in all cases. Median head station at admission was +1 (Pearson's correlation coefficient at FPA of 45° was 0.69, P < 0.001). Measured AoP values increased with maternal hip flexion with a maximal increase at hyperflexion (McRoberts' maneuver). Median AoP in the different stations were: AoP−10° = 113° (interquartile range (IQR), 103–124°); AoP0° = 121° (IQR, 113–128°); AoP45° = 122° (IQR, 109–133°); and AoP> 135° = 132° (IQR, 121–146°) (Figures 1 and 2). Median increase in AoP during full maternal hip flexion (from extended hips to hyperflexion in the McRoberts' maneuver, i.e. AoP> 135° − AoP−10°), was 17° (IQR, 10–27°; P < 0.001). For mild maternal hip flexion with change in FPAs from 0° to 45° (from lying flat to flexed knees), there was a small, non-significant difference in AoP of 1° (IQR, −4 to 6; P = 0.14). McRoberts' maneuver was originally proposed as a first-line measure for the disengagement of impacted shoulder dystocia, and for facilitating maternal pushing in the second stage of labor5. Tension and movement at the sacroiliac joints with maternal hip flexion results in posterior pelvic tilt and cephalad displacement of the pubic symphysis with a concomitant significant increase in AoP, as documented in the current study. Change in AoP with maternal hip flexion during McRobert's maneuver provides real-time bedside quantification of sacroiliac joint movement, the clinical significance of which in labor, delivery and the prevention and treatment of shoulder dystocia still needs to be studied. Given the dependency of AoP on maternal hip flexion, maternal position should be taken into account in AoP reports. In this context, it is important to note that, in mild hip flexion with neutral tilt of the maternal pelvis and change in FPA from 0° to 45°, no significant change in AoP was found, making these positions suitable for standardized reproducible AoP measurement. In conclusion, maternal hip flexion, such as in McRoberts' maneuver, significantly increases AoP. Reports including AoP should contain detailed information on maternal position, birthing bed, use of stirrups and degree of hip flexion. Until further research is available, we recommend measuring AoP in the second stage of labor with the patient in the supine position, without stirrups, at rest between contractions, with the bed headboard at 30° inclination, knees flexed at FPA = 45°, minimal external hip rotation and neutral pelvic tilt. Further studies are needed to revalidate existing AoP tables and to investigate the clinical significance of changes in AoP measurement during McRoberts' maneuver.