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A cycle in which ovulation does not occur.

Your body temperature at complete rest, taken immediately upon waking.

A cervical-mucus–only method developed by Drs. John and Evelyn Billings.

Fluid produced by the cervix that changes throughout the cycle in response to hormones.

A temporary endocrine structure formed from the empty ovarian follicle after ovulation.

The dominant hormone of the follicular phase.

The days in a cycle when intercourse can result in pregnancy, typically 5 to 7 days.

An umbrella term for methods that identify the fertile window through observation of biomarkers.

Pituitary hormone that stimulates ovarian follicle development.

The phase of the cycle from the first day of menstruation through ovulation.

Human chorionic gonadotropin, the hormone detected by pregnancy tests.

The process by which a fertilized egg attaches to the uterine lining.

A specific protocol that uses exclusive breastfeeding to delay return of fertility postpartum.

A rapid rise in luteinizing hormone that triggers ovulation roughly 24 to 36 hours later.

An NFP method developed at Marquette University that uses a hormone monitor.

Fertility awareness practiced as a means of either avoiding or achieving pregnancy without using contraception.

The release of a mature egg from the ovary.

Effectiveness when a method is used exactly as designed, with no errors.

The transitional years leading up to menopause.

A common endocrine condition that often disrupts ovulation.

The period following childbirth, during which fertility gradually returns.

The dominant hormone of the luteal phase, produced by the corpus luteum.

The stretchy, elastic quality of cervical mucus near ovulation.

Effectiveness as actually practiced by users, including occasional errors.