Is there a decline in female fertility?

In many developed countries the average number of children born per woman has declined significantly during recent decades. This was mainly due to changes in socioeconomic factors and behavioral changes, such as postponement of childbearing. In addition to the these developments a general decline in human fertility was postulated. Several reports indicated a possible decrease in semen parameters during the last decade, whereas couple fertility seemed to have increased instead. However, currently available publications are heterogeneous in terms of study design, defined endpoints or definition of fertility and at present no definite conclusions can be drawn. Additionally, there are multiple lifestyle factors which interfere with human fertility. Individual counselling of patients should cover basic biological information, e.g. reduced fertility at increased maternal age and individual risk factors. In general, more well designed studies on human fertility are needed.