Several features of today’s lifestyles, particularly the increasing numbers of women remaining childless and the general tendency to postpone childbearing, explain the low fertility in many countries. A substantial proportion of postponers are not fully aware of the steep drop in fecundity after the age of 30-35; other women know about the loss but place their confidence in the “magic” powers of IVF; many others know about the decrease but nevertheless postpone childbearing because of a lack of acceptable alternatives. In fact, IVF cannot make up for all births lost by postponement and although vitrification seems to hold out promise for indefinitely storing oocytes for social reasons it is still an experimental procedure. Other lifestyle variables can contribute to reducing fecundity at any age, and the following in particular merit examination:• undernutrition in the woman • overweight in women and men• smoking and alcohol use by either sex.Obesity in particular - a very frequent problem – raises the risk of infertility and reduces the success of all profertility treatments. Smoking too (30% of women in the rich countries) can reduce fecundability and cause premature reduction of the ovarian reserve. In addition, smoking during pregnancy causes a loss of ovarian follicles in the offspring.