[Sirenomelia. Review of nosology and a case report]

We report a case of sirenomelus observed at 21 weeks amenorrhoea with oligoamnios. This syndrome results from an anomaly during the fourth week of gestation perturbing development of the lower limbs and the pelvis. Normal differentiation of the sexual organs, urinary tract and terminal intestine is interrupted. Recent progress in embryopathology has led to identification of a caudal regression syndrome but the aetiology remains unknown as is the nature of the relationship with VATER association.