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Overview
This page provides basic health information about the female fertility cycle. The intent of this content is to quickly bring a clueless VTuber fan up to speed, not for medical advice.
You can find more detailed information at medical websites, like the UC Davis website on OBGyn.
Basics
The fertility cycle varies widely among women, and even between cycles for a single woman. The length of a cycle, intensity, physical and mental effects can widely vary. Many factors influence the underlying hormones and physical processes of the body.
Female hormones fluctuate in a cycle that sometimes lasts about one month. The cycle consists of four stages: menstrual → follicular → ovulation → luteal.
The cycle starts on the first day of the menstrual phase. The menstrual phase often means vaginal bleeding, because the uterine lining is breaking down and leaving the body. It can last from a couple days to a couple weeks.
The ovulation phase occurs approximately mid-cycle. It lasts about 1-2 days. It involves the release of an egg from an ovary. It can be detected through carefully monitoring basal body temperature.
A woman can get pregnant if sperm is present together with an egg. Sperm can stick around about a week, so she is fertile about a week before ovulation and a few days after.
The follicular phase causes an egg to develop. It can be a happy relatively painless time in the cycle.
The luteal phase builds up the hormones required to begin the menstrual phase. These hormones and some common health complications can cause pre-menstrual pain and negative mental states.
Complications
The following information was sourced from hopkinsmedicine.org and health.ucdavis.edu. Percent occurrences were sourced from various websites. This is not a comprehensive list.
Each woman's experience with these is different.
If you are a worried woman somehow reading this, or you are worried about a woman in your personal life, try keeping a diary of periods and symptoms and bring it to an ObGyn appointment. (Nothing on this page or website is medical advice.)
PMS (Premenstrual Syndrome)
Causes physical and emotional symptoms before a period, that stop after the period starts.
Diagnosed based on a journal of symptoms for several months of the onset and duration of the symptoms in relation to periods.
No known cure. No known causes. Treatment with lifestyle changes and sometimes medicine.
It causes anxiety, back aches, headaches, tender breasts, trouble concentrating, constipation or diarrhea, and other symptoms.
Occurs in 90% of women.
PMDD (Premenstrual Dysphoric Disorder)
No known cure. Exact cause not known. Treatment with lifestyle changes, certain supplements, and medicines.
Diagnosed based on a diary of symptoms before a period starts and whether they are still there a few days after a period starts.
A severe form of PMS. Its symptoms make daily life difficult.
It can cause depression, migraines, feelings of worthlessness, increased anxiety, mood swings, feeling overwhelmed, and other mental debuffs.
It can cause physical symptoms including breast swelling and tenderness, headaches, muscle pain, and self-harm.
Occurs in 2-5% of women.
PCOS (Polycystic Ovary Syndrome)
No known cure. No known cause. Treatment with medicine.
Diagnosed by examination.
Causes pain and lowers fertility.
Sometimes ovulation doesn't occur and fluid-filled sacs form in the ovaries. These cysts can cause more issues and pain.
Occurs in 5-15% of women.
Endometriosis (Endo)
Cause uncertain. Treatment with hormones, pain management, small medical procedures, or larger surgery.
Diagnosed by a small medical procedure. Sometimes signs of it can show up in ultrasounds or MRIs.
Can cause pain, diarrhea or constipation, fatigue, heavy or irregular periods, more pain, spotting between periods, infertility, or other symptoms.
The tissue that normally lines the inside of the uterus is called the endometrium. It normally is shed and regrows every cycle. This complication occurs when this tissue occurs outside of the uterus. The buildup of this tissue causes inflammation, scarring, cysts, and other issues.
Occurs in 2-10% of women.
Ruptured Ovarian Cyst
Treated with emergency surgery if it causes complications.
Diagnosed by examination.
Causes sharp abdominal pain, fever, and nausea, and requires a medical inspection immediately.
While ovarian cysts are common, they can rupture or twist and cause further issues.
Uterine fibroids
Cause not known. Treatment normally not needed, but can include medicine or surgery.
Diagnosed, usually found during a routine exam or imaging.
Symptoms include heavy and prolonged periods, intraperiod bleeding, pain and pressure.
This is a common condition where noncancerous tumors develop in the uterus.
Occurs in 20-50% of women.
Menorrhagia (Heavy Menstrual Bleeding)
Caused by hormonal imbalance, another underlying issue, pregnancy issues, or an IUD. Treatment with medicine, iron supplements, or surgery.
Causes prolonged bleeding, changing pads or tampons every 1-2 hours because it is soaked, having spotting or bleeding between periods, or passing large clots.
Occurs in 20% of women.
Dysmenorrhea (Severely Painful Cramps)
Can be caused by a chemical imbalance (primary), or another underlying issue (secondary). Treatment can include normal period care, hormones, surgery, or other treatments.
If secondary, it can be diagnosed via examination.
Causes many extremely painful cramps during a period, which can occur in the lower abdomen, lower back, or down the legs. Also causes nausea, vomiting, diarrhea, weakness, fainting, or headaches.
Mild cramps occur in 60% of women. Cramps so severe that the pain affects daily activities occur in 5-15% of women.
Myths
These are myths I have seen circulate in the VTubing sphere. Perhaps they started as memes, but sex ed can be lacking, so some people believe them. I believed one before studying this topic.
These myths are busted.
❌ Period syncing
Also known as menstrual synchrony, this refers to the belief that women who live in close proximity will eventually "sync", in other words, have their periods at the same time.
The original study suggesting this phenomenon was debunked.
❌ Birth control is only used by women who have intercourse
Birth control is sometimes used to reduce intense period pain, to try to skip a period that would otherwise come at an inconvenient time, or for other reasons.
❌ Cycles are only tracked by women who have intercourse
Tracking cycles is important for the health of many women. Tracking the fertility cycle is also useful to guess when periods will be, to plan around them.
❌ Missing or delayed period means pregnancy
Hormones can be affected by stress, diet, or the environment. A missed or delayed period can just happen sometimes.