Mirror syndrome is a rare entity describing the association of foetal hydrops and maternal symptoms as general oedema and excessive weight gain mimicking preeclampsia. We report the case of a patient who developed symptoms of oedema, weight gain, headache and biological hemodilution associated with foetal hydrops due to a complex congenital heart defect. This symptomatology spontaneously resolved after foetal expulsion. Mirror or Ballantyne's syndrome needs to be identified on time and well differentiated from preeclampsia. Its consequences may involve the maternal and foetal prognosis.