Ovarian hyperstimulation syndrome (OHSS) mostly occurs as a complication of induction of ovulation. However, rarely, it may occur spontaneously at the beginning of a natural pregnancy and in the absence of any assisted reproductive treatment. Spontaneous OHSS has been reported in pregnant women affected by hypothyroidism, polycystic ovary syndrome, gonadotropin-producing pituitary adenoma, but also in normal pregnancies. The aetiology of this condition is still unclear. We hereby report on a case of spontaneous, familial, recurrent OHSS in a 26-year-old primipara whose first-degree cousin, paternal grandmother and a number of other members of her father's family had suffered from a similar condition. This case seems to support the concept of a genetic predisposition for spontaneous OHSS thereby suggesting the need for preventive and therapeutic strategies.