This article may require cleanup to meet Wikipedia's quality standards. The specific problem is: due to unclear definitions for fertility, fecundity and derivative terms depending on whether the term is being used in demography, epidemiology or clinical medicine. For example fecundity is the potential to for a female to become pregnant and carry that pregnancy to a live birth in demography, while in clinical medicine it refers to actual production of live offspring. Please help improve this article if you can.(March 2019) (Learn how and when to remove this template message)
Human demography considers only human fecundity, at its culturally differing rates, while population biology studies all organisms. The term fecundity in population biology is often used to describe the rate of offspring production after one time step (often annual). In this sense, fecundity may include both birth rates and survival of young to that time step. While levels of fecundity vary geographically, it is generally a consistent feature of each culture. Fecundation is another term for fertilization. Superfecundity or retrofecundity refers to an organism's ability to store another organism's sperm (after copulation) and fertilize its own eggs from that store after a period of time, essentially making it appear as though fertilization occurred without sperm (i.e. parthenogenesis).
Fecundity is important and well studied in the field of population ecology, though it is studied from a neutral perspective. Fecundity can increase or decrease in a population according to current conditions and certain social factors. For instance, in times of hardship for a population, such as a lack of food or high temperatures, juvenile and eventually adult fecundity has been shown to decrease (i.e. due to a lack of resources the juvenile individuals are unable to reproduce, eventually the adults will run out of resources and reproduction will cease). Additionally, social trends and societal norms may influence fecundity, though this influence tends to be temporary. Indeed, it is considered impossible to cease reproduction based on social factors, and fecundity tends to rise after a brief decline.
^Etienne van de Valle (adapted by), from the French section edited by Louis Henry (1982). "Fecundity". Multilingual demographic dictionary, English section, second edition. Demopaedia.org, International Union for the Scientific Study of Population. p. 621-1. Retrieved 8 February 2010.