Does Sex Affect the Menstrual Cycle?
Can sexual activity impact the menstrual cycle? Keep reading to learn about the relationship between the menstrual cycle and libido, pregnancy, sexual activity, and more.
You may have heard that sex can improve your cramps, speed up your menstrual cycle, or delay your period. While some of these claims may not be true, sex and the menstrual cycle are connected in other ways.
The menstrual cycle
The menstrual cycle is a four-phase cycle that is about 28 to 35 days on average.  Menstruation marks the beginning of one cycle, then the follicular phase continues, which is when the ovaries are being stimulated and continue to develop mature follicles. Ovulation is the third phase, marked by the release of a mature egg from a developed follicle. Luteal phase is the last step, when the body is preparing for an embryo to implant into the uterus.
These phases occur as a result of hormones fluctuating and communicating with the brain, ovaries, fallopian tubes, and more.  The menstrual cycle may be impacted by various factors such as age, genetics, lifestyle, thyroid disorders, endocrine disorders, and more. 
How sex and the menstrual cycle are correlated
The most robust data we have to connect sexual activity and the menstrual cycle is related to pregnancy. The fertile window surrounding ovulation is when pregnancy is most likely to occur from heterosexual sex.  If conception does happen, a missed period is usually one of the early signs of pregnancy and periods will discontinue until about six to 24 weeks after giving birth.  Outside of this, sexual activity is not likely to have an impact on the menstrual cycle in terms of regularity or length. Some have suggested that the rise in hormones during sex such as oxytocin may have an effect on the menstrual cycle, and that having sex may shorten periods or lessen period symptoms, but there is little data to support these claims. If your period is late or seems abnormal and you’ve had sex recently, you may want to take a pregnancy test to ensure you aren’t pregnant.
Can I have sex on my period?
Absolutely! Whether or not you choose to participate in sexual activity during your period is up to you and your partner. You may want to have a conversation about condom use given the increased exposure to blood and the ability to transmit various infections such as HIV or hepatitis. With disease risk aside, there should be no harm in having sex while menstruating.
Interestingly, there has been a study researching the perceptions of different women surrounding period sex. It was found that white, bisexual, and lesbian women have more positive feelings surrounding sex during menstruation compared to women of color and heterosexual women.  Positive responses were focused on pleasure and rebellion against anti-menstrual attitudes, whereas negative responses involved discomfort, negative self-perception, partner disgust, and the labor associated with cleaning up any “messes.” 
Menstrual cycle and libido
There are associations between certain phases of the menstrual cycle and sexual desire. A study found that more women, both partnered and single, were more sexually active in the days prior to and including the preovulatory surge.  This refers to a surge of luteinizing hormone (LH), the hormone responsible for ovulation.
What else impacts the menstrual cycle?
Potential menstrual cycle irregularities could include light or shortened periods, painful periods, abnormal ovulation, heavy bleeding, spotting, prolonged menstruation, and more. The menstrual cycle may be impacted by many different factors, including: 
- Hormonal birth control
- Thyroid conditions
- Unmanaged diabetes
- Excessive exercise
- Intense weight fluctuations
- Polycystic ovary syndrome (PCOS)
- Untreated STIs/Pelvic scarring
The average menstrual cycle is about 28 to 35 days, although plenty of people do fall outside of this range.  If you’re having recurrent irregular periods or other menstrual cycle irregularities, you should see your healthcare provider. You may also benefit from testing your hormones, which may give you some insight into why your menstrual cycle may be abnormal.
Sex and the menstrual cycle
Sexual activity and the menstrual cycle are mainly correlated in regards to libido, fertile periods, and pregnancy. In many women, there is an increase in sexual desire and sexual activity surrounding the days of ovulation, when conception is most likely to occur.  If conception does happen, a missed period is one of the first signs of pregnancy. Many will experience lactational amenorrhea, or the absence of a period while breastfeeding. Outside of pregnancy and postpartum, the menstrual cycle may also be impacted by medications, endocrine disorders, thyroid disorders, perimenopause, and more.
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