The menstrual cycle and intimacy

The cycle in brief

A cycle is counted from the first day of bleeding. Typical length is 21–35 days; the widely repeated "28 days" is an average, not a standard. Bleeding lasts 2–7 days.

• Menstrual phase (days 1–5 or so): hormones at their lowest.
• Follicular phase: oestradiol rises as a follicle matures.
• Ovulation (around 12–16 days before the next period, not necessarily day 14): the egg is released; oestradiol peaks and testosterone rises modestly.
• Luteal phase: progesterone dominates; if no pregnancy occurs, both hormones fall in the last few days, triggering menstruation.

Wilcox et al. (2000, BMJ) showed the timing of ovulation is far more variable than the textbook model implies: only about 30 percent of women had their fertile window entirely within days 10–17.

Desire across the cycle

There is a documented mid-cycle rise in sexual desire and in initiation around ovulation, associated with peak oestradiol and rising testosterone. Roney and Simmons (2013), measuring daily hormones and desire, found oestradiol positively and progesterone negatively associated with reported desire.

The effect is real and it is modest. Individual variation exceeds the average cycle effect: many people report peak desire during menstruation or in the late luteal phase, and hormonal contraception flattens the pattern. Sleep, stress, relationship context and opportunity all outweigh cycle phase in most studies. Cycle phase is a useful thing to know about yourself; it is not a schedule.

Sex during menstruation

Safe, and preferred by some people — orgasm can relieve cramps through uterine contraction and endorphin release, and additional lubrication is present.

Practical points: use a towel, or the shower. Menstrual discs (unlike cups and tampons) can be worn during penetrative sex and hold flow. Barriers matter more, not less: bloodborne pathogen transmission risk including HIV and hepatitis is higher during menstruation, and the cervix is slightly more open. Pregnancy is still possible — sperm survive up to five days, so intercourse during a short cycle's bleeding can reach an early ovulation.

Cycle-related symptoms that affect intimacy

Premenstrual syndrome (PMS) affects a large majority to some degree. Premenstrual dysphoric disorder (PMDD) affects roughly 3–8 percent and is a distinct, severe condition recognised in DSM-5 and ICD-11, with marked mood symptoms in the luteal phase resolving with menstruation. It responds to SSRIs, which can be taken luteal-phase only, and to hormonal suppression. It is not a personality problem, and prospective daily symptom rating over two cycles is the diagnostic standard.

Dysmenorrhoea — painful periods. Primary dysmenorrhoea responds to NSAIDs taken before pain starts and to hormonal contraception. Secondary dysmenorrhoea, meaning pain caused by an underlying condition, is the concern: endometriosis affects roughly 10 percent of people of reproductive age and takes an average of 7–8 years to diagnose in most health systems. Adenomyosis and fibroids similarly cause pain and heavy bleeding.

Pain severe enough to stop normal activity, pain during deep penetration, pain with bowel movements around the period, or bleeding that soaks through protection hourly are all reasons to seek assessment and to press for it. "Bad periods are normal" is the sentence that produces the 7-year diagnostic delay.

Discharge and tracking

Cervical mucus changes predictably: dry after menstruation, then sticky, then creamy, then clear, stretchy and slippery around ovulation, then thick or absent. Tracking this is useful for understanding your own pattern regardless of contraceptive intentions.

Discharge that is grey with a fishy odour suggests bacterial vaginosis; thick, white and itchy suggests candida; green, frothy or foul-smelling warrants testing for trichomoniasis and other infections. None of these are hygiene failures, and douching makes all of them more likely.

Cycle tracking apps and privacy

Cycle data is sensitive health data with legal implications in some jurisdictions. Several widely used apps have been documented sharing data with advertisers and third parties, and one settled with the US FTC in 2021 over disclosure practices. Choose an app that stores data locally or has a clear no-sharing policy, and treat any app's contraceptive claim as valid only where it is regulated as a medical device.

Sources

• Wilcox AJ et al. "The timing of the 'fertile window' in the menstrual cycle." BMJ, 2000.
• Roney JR, Simmons ZL. "Hormonal predictors of sexual motivation in natural menstrual cycles." Hormones and Behavior, 2013.
• Bull JR et al. "Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles." npj Digital Medicine, 2019.
• Yonkers KA, O'Brien PMS, Eriksson E. "Premenstrual syndrome." Lancet, 2008; ISPMD consensus on PMDD diagnosis and management.
• Zondervan KT, Becker CM, Missmer SA. "Endometriosis." NEJM, 2020.
• NICE. Guideline NG73: Endometriosis diagnosis and management.
• US Federal Trade Commission. Flo Health settlement, 2021.

Last reviewed: August 2026.