Antenatal treatment with dexamethasone in pregnancies affected by congenital adrenal hyperplasias (CAH) therefore suppresses fetal androgen production and prevents virilisation of female infants. Antenatal DXM is reported to be efficacious, preventing or ameliorating virilisation in 80–85% of cases. Materials and methods: In this study, we report a case of patient pregnant at 6 weeks; with a history of 2 children followed up for a classic form of HCS, she is admitted to our department for the administration of dexamethasone to prevent fetal virilization. Case Report: 23-year-old patient pregnant at 6 weeks, not known of having congenital adrenal hyperplasia (CAH), concept of consanguineous marriage 1 degree; she had a history of 2 children followed up for a classic form of HCS, the first died at the age of 1 and 10 months and the 2 child died on D26 of life. After having made a prenatal diagnosis where an analysis of the SRY gene on fetal circulating DNA showed the absence of this gene, which confirms the female sex of the fetus. An obstetrical ultrasound was done which objectified a pregnancy estimated at 6 weeks with suspicion of clitoral hypertrophy (At 16 weeks), in view of this observation the patient was referred to us for additional care and possible dexametasone. On questioning, the patient did not report any signs of hyperandrogenism. All evolving in a context of unquantified moderate weight loss and asthenia without signs of adrenal insufficiency. The clinical examination showed no melanoderma or slate spots, BP= 105/71mmHg, RR = 19 cycles/min. CF=81bpm? BMI = 28.68 kg/m2. Tanner: S5P5. the patient was put on 1.5 mg/d of dexamethasone divided into 3 doses.a monthly measurement of DHEAS and cortisol was requested. The Decrease of plasma concentrations of cortisol and DHEAS in the mother testifies to good fetal adrenal suppression. A low-calorie diet and monitoring of blood pressure and blood sugar to detect signs of under or overdose of corticosteroid .....