Natural fertility method of birth control is a concept developed by French

French people

The French are a nation that share a common French culture and speak the French language as a mother tongue. Historically, the French population are descended from peoples of Celtic, Latin and Germanic origin, and are today a mixture of several ethnic groups...

 historical demographer Louis Henry

Louis Henry

Louis Henry was a French historian. Founder of the historical demography and one-place study fields. His 1956 book co-written with Michel Fleury, Des registres paroissiaux à l'histoire de la population...

 to refer to the level of fertility that would prevail in a population that makes no conscious effort to limit, regulate, or control fertility

Fertility

Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity, which is defined as the potential for reproduction...

, so that fertility depends only on physiological factors affecting fecundity

Fecundity

Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...

. In contrast, populations that practice fertility control will have lower than "natural fertility" levels as a result of delaying first births (a lengthened interval between menarche

Menarche

Menarche is the first menstrual cycle, or first menstrual bleeding, in female human beings. From both social and medical perspectives it is often considered the central event of female puberty, as it signals the possibility of fertility....

 and first pregnancy), spacing out the intervals between births, or stopping child-bearing at a certain age. Such control does not assume the use of artificial means of fertility regulation or modern contraceptive methods but can result from the use of traditional means of contraception

Contraception

Contraception is the prevention of the fusion of gametes during or after sexual activity. The term contraception is a contraction of contra, which means against, and the word conception, meaning fertilization...

 or pregnancy prevention (e.g., coitus interruptus

Coitus interruptus

Coitus interruptus, also known as the rejected sexual intercourse, withdrawal or pull-out method, is a method of birth-control in which a man, during intercourse withdraws his penis from a woman's vagina prior to ejaculation...

), or from social norms or practices regarding celibacy, the age at marriage and the timing and frequency of sexual intercourse

Sexual intercourse

Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis enters a female's vagina for the purposes of sexual pleasure or reproduction. The entities may be of opposite sexes, or they may be hermaphroditic, as is the case with snails...

, including periods of prescribed sexual abstinence. Ansley Coale

Ansley J. Coale

Ansley Johnson Coale , was one of America's foremost demographers. A native of Baltimore, Maryland, he earned his B.A. in 1939, his M.A. in 1941, and his Ph.D. in 1947, all at Princeton University...

and other demographers have developed several methods for measuring the extent of such fertility control, in which the idea of a natural level of fertility is an essential component.