Disorders of sex development (DSD) represent a diagnostic challenge. The complexity and variability of DSD and their psychosocial consequences require multidisciplinary care, including obstetricians, endocrino-pediatricians, clinical geneticists, pediatric urologists, neonatologists, psychologists, as well as child psychiatrists. The clinical case described herein is a genotypic-phenotypic discordance. Indeed, the non-invasive prenatal test argued in favor of a male chromosomal sex, whereas the fetal ultrasound was rather in favor of a female phenotype. The antenatal biological explorations will likely enable us to review both the mechanisms and genes involved in sex determination and sexual differentiation. Currently, a molecular diagnosis is found in only 30-50% of cases pertaining to 46, XY. In the event of an unusual external genitalia appearance, 75% of the reported cases are related to 46, XY, the most commonly encountered being hypospadias. The etiology retained in this foetal case is idiopathic DSD, with normal testicular function and severe intrauterine growth restriction (IUGR). Despite the improved etiological and genetic knowledge of sexual differentiation, the understanding of the underlying physiopathology is still incomplete, and some clinical situations remain unresolved.