The prognostic significance of hyperextension of the fetal head detected antenatally with ultrasound.

OBJECTIVES

The purpose of this study was to evaluate the clinical significance of hyperextension of the fetal head detected by ultrasound prior to the onset of labour.

METHODS

Over a 10-year period, we retrospectively identified all fetuses who had hyperextension of the fetal head reported on antenatal ultrasound. Hyperextension referred to persistence of the cervical spine in extreme extension, with an extension angle of at least 150 degrees persisting for the duration of the scan. Follow-up information was obtained from Hospital medical records and obstetrical care providers.

RESULTS

Follow-up was obtained on 57 of the 65 fetuses (87.7%) identified over the study period. Ten of the 57 fetuses had normal structural fetal surveys and had sonographically identified resolution prior to delivery. All 10 patients delivered at term and had newborns with normal neonatal courses. Twenty-six of 57 fetuses had no sonographic findings other than persistent hyperextension, and 19 of these 26 fetuses (73%) had normal neonatal courses. Twenty-one of 57 fetuses (37%) had structural anomalies sonographically identified in addition to hyperextension of the fetal head. All 21 of these pregnancies ended in either termination or fetal or neonatal demize.

CONCLUSIONS

Although resolution of isolated hyperextension of the fetal head is associated with a normal neonatal outcome, persistent isolated hyperextension of the fetal head can be associated with either a normal or an abnormal neonatal outcome. Fetuses with hyperextended heads and antenatally diagnosed structural anomalies have dismal outcomes. The identification of a fetus with hyperextension of the fetal head should prompt a detailed search for structural abnormalities.