Look anything up.

A cycle in which ovulation does not occur.

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

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

A temporary endocrine structure that forms from the empty ovarian follicle after ovulation and produces progesterone.

A group of hormones, with estradiol the main form during reproductive years, that drives the first half of the menstrual cycle and the changes that open the fertile window.

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.

A pituitary hormone that signals the ovaries to develop follicles at the start of each menstrual cycle.

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

Human chorionic gonadotropin, the hormone produced by the developing placenta and detected by pregnancy tests.

The process by which a fertilized egg attaches to the lining of the uterus, beginning early pregnancy.

A specific, time-limited postpartum method that uses full breastfeeding and the absence of menses to delay the return of fertility.

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

The phase of the menstrual cycle that begins after ovulation and ends with the start of the next period.

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

The release of a mature egg from the ovary.

Polycystic ovary syndrome, a common hormonal condition that often affects ovulation and cycle regularity.

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

The transition years leading up to menopause, when hormone levels and cycles become more variable.

The period after childbirth, during which the body recovers and fertility eventually returns on its own timeline.

A hormone produced mainly by the corpus luteum after ovulation that prepares the uterus for a possible pregnancy and shapes the second half of the menstrual cycle.

A historical calendar-only method of estimating fertile days based on past cycle lengths.

The stretchy, elastic quality of cervical mucus near ovulation.

Effectiveness as actually practiced by users, including occasional errors.