Glossary of Natural Family Planning Terms


Refraining from sexual intercourse.


The absence of menstruation.

Basal Body Temperature


The temperature of the body at rest. Because it rises slightly after ovulation, basal body temperature can indicate when ovulation has occurred.  The temperature must be take the same way throughout the cycle (either orally or vaginally) and taken first thing in the morning, at awakening, before activity.

Billings Method

See Cervical Mucus Method.

Birth Control

A means of family planning. The voluntary limitation or control of the number of children conceived.


The act of suckling, on the part of the infant, and the act of giving mild directly to the infant, on the part of the mother.

Calendar Method (Rhythm Method)

A method in which the fertile phase of the menstrual cycle is determined by calculating the length of at least six previous menstrual cycle. The beginning of the fertile phase is determined by subtracting 18 to 21 from the length of the shortest menstrual cycle.  The end of the fertile phase is determined by subtracting 9 from 11 from the longest menstrual cycle.  When used alone, the calendar method may be unreliable, especially for women with irregular menstrual cycles, and may be overly restrictive for some couples

Couple to Couple League (CCL)

The largest U.S. provider of natural family planning services. This organization teaches the Sympto-Thermal Method.

Cervical Mucus

A fluid of varying consistency produced by the cells in the cervical crypts.  The secretion of cervical mucus is controlled by estrogen and progesterone.

Cervical Mucus Method

A method of NFP developed by Drs John and Evelyn Billings. A woman determines her days of infertility, possible fertility, and greatest fertility by observing changes in her cervical mucus and sensations in the vulva.  To avoid pregnancy, abstinence is practiced during the fertile period.  The Billings Method refers to the “authentic” method as outlined and modified by Drs. Billings.  Several adaptations of this method, and the rules for observing the mucus and practicing the method, have been developed.  These modified, generic methods are referred to as cervical mucus methods.


The neck of the womb.


The conscious use by sexually active people of chemicals (spermicides), drugs (hormones), devices (condoms, diaphragms, intrauterine devices), surgery or behaviors to prevent pregnancy.

Corpus luteum (yellow body)

A small yellow gland that develops in the ovarian follicle after ovulation.  It secretes the hormone progesterone.


A line drawn on a basal body temperature chart to separate the lower temperature days that occur before ovulation from the higher temperature days that follow ovulation. A horizontal line - the coverline - is drawn about .05oF or .10C above the highest point of the low phase temperatures. 

Creighton Model

A type of natural family planning described as a standardized modification of the Billings Ovulation Method.


Measurement of the extent to which a purpose or objective is achieved

Egg (Ovum)

The female reproductive cell (gamete).


The developing organism from conception to about the eighth week of pregnancy.


The inner lining of the uterus composed mostly of functional tissue, mucus, and blood that develops during each menstrual cycle in response to female sex hormones.  In pregnancy the early embryo implants in the endometrium. If no pregnancy occurs, part of the endometrium is shed during menstruation.

Estrogen (Or Oestrogen)

The hormone responsible for the feminine characteristics in women. It is present during the whole menstrual cycle but especially abundant before ovulation, when it stimulates the fertility signs

Family Planning

Methods used by sexually active people to prevent, space or achieve pregnancy in order to attain the desired family size.


The process of uniting the sperm and the ovum.  Fertilization normally occurs in the outer third portion of the fallopian tubes.


The ability to reproduce: the ability of and man to father a child and a woman to conceive and carry a pregnancy to term.

Fertility Awareness

Basic information and education on male and female reproductive anatomy and physiology as is relates to fertility. For a woman, this includes the ability to identify and interpret the signs, symptoms, and patterns of fertility throughout her menstrual cycle.  For a man, it includes understanding his own reproductive potential.  For both women and men, it contributes to their knowledge about their combined fertility at different stages throughout their lives, and to their ability to communicate about fertility issues with health provider and one another.

Fertility Cycle

The repeating monthly sequence of menstruation and ovulation where fertility systematically changes as the days progress. On average, 28 days in length.

Fertility Rate

The average number of children per woman. The replacement level is 2.1. The current fertility rate in Canada is 1.54.

Fetus (or Foetus)

The developing offspring from embryo to birth. From the Latin for 'offspring.' It is the medical term for the child in the womb (after 8 weeks.)


See fetus.


The mature reproductive cell: in males the sperm; in females the ovum.


A chemical substance produced in the body that regulates the activity of certain cells or organs.


The normal process in which the blastocyst becomes attached to the endometrium. In abnormal situations, the blastocyst may attach itself to the fallopian tubes, or less frequently, to organs within the abdominal cavity, threatening the mother’s life by hemorrhage when the placenta grows into a blood vessel.


The inability to reproduce: the inability of a man to father a child or of a woman to conceive and carry a pregnancy to term.

Lactational Amenorrhea Method (LAM)

LAM is an introductory postpartum family planning method.  If a woman is amenorrheic, is fully or nearly fully breastfeeding day and night, and is less than six months postpartum, she is 98% or more protected against an unplanned pregnancy.  It should be noted that this method does not fit the WHO definition of NFP since it demands no abstinence.

Luteinizing Hormone ( L.H.)

The hormone that stimulates the release of the egg.


The end of menstruation, which is usually considered permanent when there is no menstruation for 12 months.  During premenopause fertility gradually ceases, menstrual cycles may vary greatly in length and fertile mucus becomes less frequent.  Some women experience hot flashes as part of the physical and mental changes associated with menopause. The menopause signals the end of ovarian function.

Menstrual Cycle

The entire cycle of physical changes from the beginning of one menstruation to the beginning of the next. During this period hormones produced by the ovaries cause the endometrium to shed and develop anew.

Menstruation (or Period; or Menses)

The cyclic discharge of the lining of the endometrium (menstrual blood, cellular debris, and mucus) that occurs about 2 weeks after ovulation if the woman is not pregnant.  Also called menses or period.

Method Effectiveness

A measure of how well a method prevents pregnancy when it is consistently and correctly used

Natural Birth Control

Family planning methods that do not use pharmacological, surgical or mechanical means, or behaviours that interfere with the natural end of the sexual act.

Natural Family Planning

Methods for planning and preventing pregnancies that are based on observing the naturally occurring signs and symptoms of the fertile and infertile phases of the menstrual cycle.  To avoid pregnancy, couples using natural family planning abstain from intercourse during the fertile phase of the woman’s menstrual cycle.  No drugs, devices, or surgical procedures are use to prevent pregnancy.  When sexual intercourse occurs, withdrawl is not used.  Natural family planning methods include the Cervical mucus or Billings Ovulation Method, the Calendar Mthod and the Symptothermal Method.  The Lactational Amenorrhea Method (LAM) is often included as a natural family planning method, although is does not require abstinence from intercourse.


Natural Family Planning.


See Ovum.


See estrogen.

Ogino Knaus Method

See Calendar Method. Named after two scientists who developed it.

Ovum (plural: Ova)

The mature female reproductive cell.  Also known as an egg.


The process in which the ovum is released from the mature follicle.  Ovulation usually occurs 10 to 16 days before the next menstruation. The ovum is capable of being fertilized for about 10 hours after ovulation but probably no more than 24 hours.

Ovulation Method

See Billing’s Method or Cervical Mucus Method.


A common term for menstruation.

Periodic Abstinence

Intentional avoidance of sexual intercourse on fertile days to prevent pregnancy.


Immediately prior to ovulation, (within 24 hours before ovulation.)

Pregnancy (Pregnant)

The state of a female after she has conceived until she gives birth.


The time period approaching menopause.


One of the two major female sex hormones, produced primarily by the corpus luteum.  Progesterone stimulates the development of the endometrium to make it ready for implantation. It is also responsible for the rise in basal body temperature and the change of fertile-type mucus to infertile-type mucus after ovulation.


The hormone produced by the pituitary gland that causes the breast to produce milk.  High levels of prolactin are usually associated with menstrual irregularities and infertility.

Relatively Infertile Period

The period of time before ovulation, with no signs of fertility, where the probability of pregnancy is very low but not zero. The word “relatively” is used in comparison to the 'definitely' infertile period after ovulation.

Rhythm Method

See Calendar Method.


A Canadian natural family planning organization that teaches and develops the Sympto-Thermal Method. Founded in 1955 in Quebec. Pioneer of the Sympto-Thermal Method.

Sexual Intercourse

The physical union of male and female genitalia when the penis enters into the vagina.

Sperm (Spermatozoon, Plural: Spermatozoa)

The mature male reproductive cell.  The sperm is able to fertilize the ovum for at lest 72 hours after ejaculation in the presence of fertile cervical mucus.


See sperm.


A very small amount of bleeding from the vagina.

Symptothermal Method (ST Method; STM)

The method of natural family planning taught by Serena, in which the fertile and infertile days are identified by observing and interpreting cervical mucus, basal body temperature, and other signs and symptoms of ovulation.  The other signs and symptoms include intermenstrual bleeding, breast tenderness, abdominal pain, and cervical changes.

Theoretical Effectiveness

The effectiveness of a method of avoiding pregnancy when used perfectly. 

Use Effectiveness

A measure of how a method prevents pregnancy under conditions of usual practice.  The use-effectiveness refers to the number of pregnancies occurring among 100 women for one year as a result of the method itself (method related) and the way the method is used.  Incorrect method use in natural family planning may be due to incorrect teaching or misunderstanding of method rules (teaching related), or lack of adherence to the rules (i.e. abstinence during the fertile phase), despite the couple’s stated intention to avoid pregnancy.

Definitions taken from: Institute of Reproductive Health. Glossary of Natural Family Planning Terms Second Ed.  Georgetown University, Washington DC. 1993. 

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