Diagnostic de l’engagement fœtal par l’échographie transpérinéale : étude préliminaire tunisienne

Assessment of fetal head engagement with transperineal ultrasound: Searching for the cutoff level

PURPOSE

Engagement of the fetal head is a determinant element when deciding on operative vaginal delivery. In routine practice, engagement is a clinical diagnosis based on transvaginal digital examination. Transperineal ultrasound might provide complementary information useful for measuring the fetal head-perineum distance (HPD). The purpose of this work was to determine the cutoff HPD distinguishing engagement from non-engagement.

MATERIALS AND METHODS

This single-center prospective study approved by the institutional review board was conducted between December 25, 2012 and August 31, 2015 in 411 nulliparous women; 20 did not provide informed consent and were excluded; analysis concerned 391 patients. Clinical diagnosis - engagement or non-engagement depending on results of the transvaginal digital examination (Farabeuf's and Demelin's signs) - was compared with the ultrasound HPD measurement.

RESULTS

The clinical diagnosis was non-engagement at complete dilatation in 96 patients (24.6%). The cutoff HPD distinguishing between engagement and non-engagement was 57mm (AUC 83.5% [95%CI 79.3-87.8]), with 75.0% [65.5-82.6] sensitivity, 75.9% [70.7-80.5] specificity, 50.3% [42.2-58.4] positive predictive value, and 90.3% [86.0-93.4] negative predictive value.

CONCLUSIONS

In this series, the HPD cutoff distinguishing between engagement and non-engagement was 57mm. Below this cutoff level, the head should be considered engaged, beyond non-engaged. Nevertheless, the pertinence of this cutoff level is hampered by the imprecision of the gold standard used for the clinical diagnosis (transvaginal digital examination). In case of doubt, we recommend, in addition to considering the obstetrical setting, to combine transperineal ultrasound with transvaginal digital examination to avoid deleterious failure of operative vaginal delivery.

[Instrumental delivery with perineum-fetal head distance >55 MM on ultrasound]

OBJECTIVE

Compare the issue of an operative vaginal delivery associated to the fetal presentation diagnosed by transperineal ultrasound. Three groups were formed: ≥55 mm, between 45 and 55 mm, and <45 mm.

METHODS

A monocentric prospective study on 108 patients has been conducted between April 2011 and August 2014. The distance between perinea and skull has been analyzed to compare the success of operative vaginal delivery considering the level of the fetal presentation in the pelvic cavity.

RESULTS

The failed operative vaginal deliveries are more frequent while the fetal head is above 55 mm (16.7%) or while the fetal head is between 45 and 55 mm (9.1%) than while the fetal skull is under 45 mm (1.8%) (P=0.04). However there is no significant difference for the fetal shoulder dystocia (5.6% vs 3.0% vs 3.5%, P=0.5), nor for the newborn outcomes (16.7 vs 15.2 vs 14; P=0.9).

CONCLUSION

Despite the high rate of failed operative vaginal delivery above 55 mm, it should be considered not to prohibit but send free to the obstetrician appreciation.