What the cycle does to the body

Cramps

Cramps happen when the uterus contracts to shed its lining. The trigger is a group of natural chemicals called prostaglandins, which are made in the lining of the uterus. Prostaglandins make the muscles and blood vessels of the uterus contract.¹

• Levels rise right before a period starts, and they are high on the first day.^1,2
• As bleeding continues and the lining is shed, levels fall. That is why cramps usually ease after the first few days.
• Experts think people with more painful periods may have higher prostaglandin levels. For some people there may be no clear explanation.²
• Pain relievers called NSAIDs, like ibuprofen and naproxen, reduce the prostaglandins the body makes. That is how they ease cramps.

The medical word for painful periods is dysmenorrhea. Pain that starts days before a period, gets worse over time, or lasts longer than usual can have another cause, such as endometriosis or fibroids. Talk to a doctor if that sounds familiar.

Dive deeperWhat makes the uterus create prostaglandins?+

Headaches

Some people get headaches around their period. For people with migraine, research has found two causes: a fall in estrogen and the release of prostaglandins. About 20 to 25 percent of women who get migraines have migraines linked to their period.³

Treatments that target these causes might help, but the evidence for them is not strong yet.³

Dive deeperHow can a fall in estrogen or prostaglandins cause headaches?+

Bloating and digestion

Some people feel bloated around the time of their period. One review found that about a third of women with no other digestive problems have digestive symptoms when they menstruate. About half of women with irritable bowel syndrome (IBS) report more symptoms around their period.⁴ Severe period pain can also come with nausea or diarrhea.

Three explanations have been suggested:

• Fluid retention. Progesterone is high in the luteal phase, and the body can convert it into a related hormone that makes the kidneys hold on to sodium and water.⁵ One source estimates about a pound of weight gain from fluid during a period.⁶
• A slower gut. The gut has receptors for estrogen and progesterone, so it responds when they shift. Progesterone may slow how fast food moves through, which can cause gas and constipation.^6,7
• Prostaglandins. The same chemicals that make the uterus contract may also affect the gut muscles and how sensitive the gut is to pain, which could explain bowel changes that come with cramps.⁷

Some things that are commonly suggested to help are drinking enough water, eating less salt and sugar, and regular exercise.⁶ A doctor can help if bloating comes with weight changes, severe pain, blood in the stool or lasting changes in bowel habits.⁶

Breast tenderness

Breast pain linked to the cycle usually starts up to 2 weeks before a period, gets worse, and goes away when the period ends. It is the most common kind of breast pain, affecting about two thirds of people who have breast pain. It is linked to the hormone changes of the cycle and is strongest in the luteal phase.⁸

A common explanation is that estrogen makes the milk ducts in the breast larger and progesterone makes the milk glands swell, even without pregnancy or breastfeeding.^9,10 Soreness can also start before ovulation, when estrogen is rising, and it varies a lot from person to person.^11,12

Some points worth knowing:

• Sore breasts or nipples around ovulation are not a reliable sign of ovulation. They also can't be an early sign of pregnancy, because the days right after ovulation are too early for pregnancy symptoms.¹¹
• Other causes include friction from clothing or running, an allergic reaction to a soap or detergent, some medicines and breastfeeding.¹² An injury or an infection of the breast (mastitis) can also cause soreness.¹¹
• A supportive, well-fitting bra, pain relievers and less salt are often suggested. Whether cutting caffeine or dietary fat helps is unclear.^8,9

See a doctor for a lump, a change in the shape of the breast or nipple, dimpled skin, a rash, nipple discharge, redness or heat, pain that is one-sided or doesn't follow the cycle.^10,12

Skin

The hormones that run the cycle influence the oil glands in the skin and how oily or dry the face feels.¹³ Extra sebum (oil) is one part of how acne forms, along with clogged pores, bacteria and inflammation.

Many acne-prone people get flare-ups before a period. One source reports that more than 60 percent do. The flare-ups usually start 7 to 10 days before the period and get better soon after it begins.¹⁴ They tend to show up on the chin, jawline and lower cheeks, and they are often deeper, more painful bumps than usual breakouts.^15,16

Sources describe the cause a little differently, but they share the idea that hormone shifts push the oil glands to make more sebum. Some point to the fall in estrogen and progesterone before a period, which leaves androgens such as testosterone relatively stronger.^14,15,17 Progesterone itself may also play a part, and swelling of the skin may squeeze the pores.¹⁴ Whatever the exact cause, extra oil plus dead skin cells clogs pores, and bacteria on the skin then cause inflammation.¹⁴

Over-the-counter products with benzoyl peroxide or salicylic acid are commonly used. A doctor can prescribe other options if acne keeps coming back, for example if it hasn't improved after about three cycles.¹⁵ Acne together with irregular periods, extra facial hair or weight gain can be a sign of polycystic ovary syndrome (PCOS), so it is worth raising with a doctor.¹⁵

Body temperature

After ovulation, while progesterone is high, core body temperature runs about 0.3 to 0.7°C higher than before ovulation, or roughly 0.5 to 1.3°F. Estrogen has the opposite effect and tends to lower it.¹⁸ The shift is easiest to see in the resting temperature on waking, called the basal body temperature. Some people use the rise to confirm afterward that they ovulated. Because it only shows up after ovulation, it can't predict it.

Vaginal discharge

Vaginal discharge is normal and keeps the vagina clean and healthy. The NHS describes healthy discharge as clear or white, with no strong or unpleasant smell. It can be thick and sticky or slippery and wet.¹⁹ A typical amount is about half to one teaspoon (2 to 5 mL) a day.²⁰

Where it comes from. Discharge is a mix, not a single fluid:²⁰

• cervical mucus, made by the cervix, which changes through the cycle
• cells shed from the cervix and the vagina
• bacteria
• water

During sexual arousal, extra fluid is also pushed through the walls of the vagina by increased blood flow. This is a separate fluid, called arousal fluid.²⁰

How it changes across the cycle:

• Around ovulation: clearer and wetter. The cervical mucus becomes slippery, like egg whites, which helps sperm move up into the uterus and fallopian tubes.^21,22
• After ovulation: progesterone makes the mucus thick and paste-like, which helps keep bacteria out of the uterus.²¹
• At the start and end of the cycle: estrogen is lower, so the vagina can feel drier.²⁰

There is usually more discharge during pregnancy, with sexual activity or with birth control.¹⁹

A change in colour, smell or texture is worth a call to a doctor. The NHS lists some patterns that can point to infection: a fishy smell (bacterial vaginosis), thick white discharge like cottage cheese (thrush), or green, yellow or frothy discharge (trichomoniasis). Itching, soreness or pelvic pain along with discharge is another reason to get checked.¹⁹ The lesson on what is normal covers these infections.