What is an unsuppressed menstrual cycle?

Understanding an Unsuppressed Menstrual Cycle

An unsuppressed menstrual cycle refers to a natural menstrual cycle that is not affected by hormonal contraceptives, allowing normal ovulation and hormonal fluctuations to occur. 1

Characteristics of an Unsuppressed Cycle

• An unsuppressed cycle follows the natural pattern of hormonal changes, including follicular development, ovulation, and luteal phase progression 1
• Typically lasts 26-35 days in most women, with approximately 5 days of menstrual bleeding 1
• Contains a fertile window spanning from 5 days before to the day of ovulation 1
• Features natural FSH rise at the luteal-follicular transition, stimulating follicular growth 1
• Includes selection of a dominant follicle in the mid-follicular phase, which secretes increasing amounts of estradiol and inhibin A before ovulation 1

Comparison with Suppressed Cycles

• In contrast to unsuppressed cycles, hormonal contraceptives (like combined oral contraceptives) suppress ovulation by maintaining consistent hormone levels 2
• Hormonal methods prevent the natural LH surge that triggers ovulation 2
• Extended or continuous use of hormonal contraceptives can eliminate the hormone-free interval entirely, maintaining suppression continuously 2
• When switching from a suppressed to an unsuppressed cycle (discontinuing hormonal contraception), backup contraception is typically needed for 7 days as the natural cycle resumes 2

Clinical Significance

• Unsuppressed cycles are necessary for natural conception, with the highest fertility occurring during the 6-day fertile window ending on the day of ovulation 3
• For women with short cycles (25 days), the fertile window in an unsuppressed cycle typically occurs between days 6-11 4
• Sexual intercourse during unsuppressed cycles is associated with cycle characteristics suggesting higher fecundability, including longer luteal phases and more days of cervical fluid with estrogen-stimulated qualities 3
• Women with unsuppressed cycles may experience cycle-related symptoms that hormonal methods often reduce, such as menstrual cramping, heavy bleeding, or premenstrual symptoms 2

Hormonal Patterns in Unsuppressed Cycles

• The hypothalamus regulates the cycle through pulsatile release of GnRH, occurring every 1-1.5 hours in the follicular phase and every 2-4 hours in the luteal phase 5
• FSH and LH are released from the pituitary in response to GnRH pulses 5
• Two-thirds of women show two follicle waves and one-third show three follicle waves per cycle in unsuppressed cycles 1
• The corpus luteum forms after ovulation, secreting progesterone, estradiol, and inhibin A in response to LH pulses 1
• The luteal phase in unsuppressed cycles typically lasts 10-14 days 3

Common Variations

• Cycle length variability is normal in unsuppressed cycles, with most women not ovulating exactly on day 14 3
• Age and parity influence cycle characteristics in unsuppressed cycles 3
• Women with three follicular waves typically have longer cycles and later estradiol rise and LH surge compared to those with two waves 1
• Luteal phase length is more consistent than follicular phase length in unsuppressed cycles 6

Understanding the characteristics of unsuppressed cycles is important for fertility awareness, natural family planning, and for women transitioning from hormonal contraceptives to natural cycles.