The reason your libido increases when you have your period- and why sex is more pleasurable during that time of the month

It's no secret your emotions change during your period, causing you to become more irritable or sensitive. 

But there is another effect you may notice during that time of the month that is spoken about in hushed tones - you're in the mood for sex more often.

From an evolutionary perspective it doesn't make the most sense as you're not at your peak fertility.  

Yet many women report heightened libido and pleasure while on their period.

Avril Louise Clarke, a clinical sexologist, said it's a mixture between an increase in vaginal sensitivity and lubrication, while others said the psychological effect of believing you can't get pregnant while menstruating can ramp up sex drive. 

The psychological effect of knowing you're less likely to get pregnant when having intercourse while menstruating could also play a role

Over a roughly 28-day menstrual cycle, women experience four stages, including menstrual, follicular, ovulatory and luteal phases. During each, hormones rise and fall, which impacts sex drive and desire. 

Ms Clarke told Refinery 29 that increased arousal during the menstrual phase - when a woman has her period - could be due to more blood flow to the pelvic area as the body sheds its uterine lining, which results in heightened sensitivity and more vaginal lubrication, leading to more enjoyable sex.

The psychological effect of knowing you're less likely to get pregnant when having intercourse while menstruating could also play a role, Dr Nicole Bullock, a Texas-based OB-GYN, told R29. 

While conceiving on your period is much less likely to happen, it's a common myth that you can't get pregnant.  

Additionally, women may also experience a small surge in testosterone, Dr Bullock added. 

Thought of as the male hormone that ramps up men's sex drives, women also have this hormone, though in lower doses.

Women 'lose six years of great sex' in their lifetime because of their period

New research estimates that women spend the equivalent of six years on their period, inspiring one brand to create the world's first menstrual cup that can be used during sex.

When it increases while a female menstruates, it may make women crave more sex. 

Rising testosterone is part of natural hormone fluctuations and is thought to play a role in fertility and the desire to have more sex in order to conceive.  

While some women report elevated desire while on their period, most will feel an increase during ovulation - 14 days before the start of menstruation - when estrogen is the highest.

Higher levels of estrogen are associated with an increase in sexual desire and vaginal lubrication.

Ovulation is when the body releases an egg into the fallopian tube where it waits to be fertilized by sperm. 

Dr Bullock said a higher sex drive during this phase 'makes sense from a reproductive standpoint.'

There are many reasons why a woman's libido will fluctuate during her cycle, but for those who do enjoy sex during their period, there are plenty of benefits, according to Heathline. 

Orgasms may alleviate cramps and sex can boost mood, combating the irritability that may accompany menstruation. 

Having your period can also provide more lubrication, making sex more enjoyable. 

Sex can also impact the duration of periods. When orgasming, the muscles of the uterus contract, which can expel uterine contents faster and shorten menstruation.