HYPOTHETICAL RISKS OF TWINNING IN THE NATURAL MENSTRUAL-CYCLE

Dizygotic (DZ) twinning is likely the result of multiple ovulation upo n multiple ongoing follicle growth. Well known conditions with an incr eased incidence of DZ twinning are a hereditary trait, high maternal a ge and ovulation induction treatments. These conditions are clearly re lated to elevation of Follicle Stimulating Hormone (FSH) at the time o f peri-menstrual follicle recruitment. In this contribution, we summar ize certain other circumstances that may occur in normal women that co uld increase twinning rate based on the assumption that the elevation of FSH levels is the principal underlying mechanism in DZ twinning. It is hypothesized that recovery from prolonged hypothalamic amenorrhea in part mimics hormonal sequelae of puberty characterized by temporary overshoot of FSH levels. By deduction, such conditions are recovery f rom lactational amenorrhea, recovery from use of oral contraceptives a nd recovery of weight loss amenorrhea. According to the literature, th ese conditions indeed carry the risk of DZ twinning and all show tempo rary elevated FSH levels. However, prospective experiments will be nee ded to prove the relation between this type of DZ twinning and possibl e patterns of serum FSH that mimic puberty under these circumstances. (C) 1997 Elsevier Science Ireland Ltd.