Hertility Health Glossary

Anovulation refers to a menstrual cycle where bleeding occurs without the release of a mature egg from the ovaries. This lack of ovulation can be a chronic or one-off event and is frequently associated with hormonal imbalance conditions such as PMOS (formerly PCOS), thyroid hormone imbalance, or high stress. Because the rhythmic rise and fall of hormones is disrupted, anovulation often results in irregular cycle lengths or unpredictable bleeding patterns.

The corpus luteum is what remains of an ovarian follicle after it has released an egg during ovulation. It acts as a temporary hormone factory, producing progesterone to thicken your womb lining and support a potential pregnancy. If there is a pregnancy, the placenta then usually takes over the role of making progesterone by the end of the first trimester. However, if there is no pregnancy, the corpus luteum breaks down, causing a dip in hormones and your period to start.

Quantity is how many eggs you have left in the ovary i.e your ovarian reserve. Quality refers to how likely an egg is to develop normally and lead to a healthy pregnancy. While we can estimate quantity with biomarkers-like hormone tests including an AMH test and FSH test-and pelvic ultrasound scan to measure AFC, we cannot measure quality. However, quality can be inferred from things like your age, lifestyle, and history.

It’s a network of glands and organs that send chemical messengers called hormones, through your bloodstream. Examples include the thyroid and ovaries. The endocrine system manages everything from your energy and mood, to your menstrual cycle. Think of this as your body's wireless communication network.

Fecundity is the biological capacity of an individual or a couple to conceive and produce a live birth during a specific period. It is often measured by observing the time it takes to become pregnant, with symptoms of reduced fecundity including irregular cycles or difficulty conceiving after a year of regular unprotected sex. Unlike fertility which refers to actual births, this term focuses on the potential for reproduction and can be influenced by age, health conditions, and environmental factors.

Roughly 6 days per cycle when pregnancy is possible. This includes the 5 days leading up to ovulation and the day of ovulation. This is because even though the egg can survive only 12-24 hours once released, sperm can live in the female reproductive tract for up to 5 days.¹ Using an ovulation calculator can help you identify these days.

Female fertility is the body’s natural capability to conceive. It’s a complex balance of many factors, including the quality and quantity of your eggs, the health of your reproductive organs, and the timing of your period cycle.

Male fertility is the ability to conceive a child. It depends on the body’s ability to produce and deliver healthy sperm and is influenced by the quality and quantity of your sperm, as well as balanced hormone levels and overall lifestyle health.

Follicle refers to a small, fluid-filled sac on the ovary that contains an immature egg. Each menstrual cycle, FSH signals a group of follicles to grow. As they grow, they release oestrogen to prepare the body for ovulation and help the uterine lining develop.

The follicular phase begins on day one of your menstrual cycle i.e. the first day of your period (the first day you bleed) and ends on the day of ovulation. This first half of the menstrual cycle is driven by a rise in FSH levels, which causes the follicles to develop and produce oestrogens, which then helps thicken the uterine lining. It is the phase most responsible for differences in total cycle length.²

The hypothalamic-pituitary-ovarian (HPO) axis is the complex communication network between your brain and your ovaries that regulates your menstrual cycle. It begins in the hypothalamus, which signals the pituitary gland to release FSH and LH, which then tell the ovaries to produce oestrogen and progesterone. This feedback loop ensures that your hormones stay balanced, triggering ovulation and menstruation each month.

The hypothalamus is a brain region that act as the command centre for the endocrine system. It sends and receives vital signals to/from the rest of your body to regulate everything from your menstrual cycle and ovulation, to your temperature and mood.

Irregular periods occur when your menstrual cycle falls outside the typical 21 to 35 day² range or varies significantly each month. This often signals that ovulation is unpredictable. Common causes include PMOS (formerly PCOS), high stress, or fluctuations in thyroid levels.

Libido refers to your sexual drive, which is influenced by a complex mix of hormones. In women, too little testosterone or oestrogen can cause a drop in desire. Changes in your libido are often a key indicator of hormonal imbalance, perimenopause, or high stress.

The luteal phase is the last phase of the menstrual cycle. It starts at ovulation and lasts until the day before your next period. During this phase the empty follicle left behind after ovulation becomes the corpus luteum. This structure secretes progesterone to prep and stabilise your uterine lining. If no egg is fertilised and there is no pregnancy, hormone levels drop and a new period cycle begins. This is also the phase during which PMS would occur.

Menarche is the clinical term for your very first menstrual period, which typically occurs during puberty between the ages of 9 and 15³. It is a major biological milestone signaling that the ovaries have begun the process of ovulation.

The menstrual cycle is a recurring cycle of changes in the uterus and ovaries, accompanied by hormone level changes throughout.These steps help the body prepare for a possible pregnancy. It’s driven by a rhythmic rise and fall of oestrogen / estrogen and other hormones.

An oocyte is an unfertilised egg cell that matures within the fluid filled ovarian follicles before it is potentially released during ovulation. These cells can exist in either an immature or mature state, and once a mature oocyte leaves the ovary, it travels into the fallopian tube to await fertilisation.

Ovarian reserve refers to the estimated number of immature eggs remaining in the ovaries. Every biological female is born with an egg count that naturally declines with age. While it does not indicate egg quality or guarantee chances of natural conception, measuring your egg reserve provides vital insight into your reproductive health and is a key factor in planning for egg freezing or fertility treatments.

Ovulation is the biological process where a mature egg is released from the ovary into the fallopian tube, typically triggered by a sharp rise in luteinising hormone known as an LH surge. This event occurs mid cycle and the days around it are called the fertile window. Regular ovulating depends on a precise feedback loop between the brain and the ovaries. It also marks the end of the follicular phase. While often linked to Day 14, timing varies: in short cycles it occurs early, in long cycles it is delayed, and in anovulatory cycles, it may not happen at all.

Your period is the bleed that happens when you aren’t pregnant and your body sheds its womb lining. Day one of your period is considered as day one of the menstrual cycle. It is triggered by a sudden drop in hormones like progesterone and signals the very start of a new menstrual cycle.

Primary sexual characteristics are the physical structures present at birth that are directly involved in reproduction, such as the ovaries, fallopian tubes, uterus, and vagina. These organs form the foundation of your reproductive system and are responsible for producing eggs and supporting a potential pregnancy.

Primary sexual characteristics are the physical reproductive structures present at birth, including the testes, penis, and scrotum. These organs are the foundation of the male reproductive system and are responsible for the production of sperm and the secretion of testosterone.

The pituitary gland is a tiny pea-sized part of the brain that acts as one of the body’s hormone messengers. It receives orders from the hypothalamus and releases the specific hormones LH and FSH needed to trigger ovulation and manage your overall reproductive health.

Pregnancy is the period of time, usually lasting about 40 weeks⁴, during which an embryo and then a foetus develops inside a person’s uterus. Common early symptoms include a missed period, morning sickness, and breast tenderness, while later stages often bring physical changes like fatigue and backaches. Throughout this process, the body undergoes significant hormonal and physical shifts to support the growing foetus until the final stage of labour and birth.

Puberty is the transitional phase where the body undergoes a surge of hormonal changes to reach reproductive maturity, typically beginning between the ages of 8 and 13⁴. Triggered by the brain, hormones like FSH and LH signal the ovaries to produce oestrogen, leading to the development of secondary sexual characteristics and the start of the menstrual cycle.

Puberty is the developmental stage where the brain signals the testes to begin the production of sperm and high levels of testosterone. This hormonal shift triggers physical maturation and the transition to reproductive adulthood, typically occurring between the ages of 9 and 14⁴, which is a bit later than females.

Reproductive health encompasses more than just the capacity to conceive; it includes the ability to have children and the liberty to choose if, when, and how frequently to do so. It is a state of overall physical, mental, and social well-being and not merely the absence of disease. It covers everything relating to your reproductive system functioning, ensuring you have the support to manage hormonal health at every stage of life.

These are the parts of the body that work together to manage fertility. Female organs include the ovaries, fallopian tubes, uterus, cervix, and vagina. Male organs include the testes, scrotum, epididymis, vas deferens, seminal vesicles, prostate gland, and penis. Monitoring the health of your reproductive organs is a key part of understanding your overall reproductive health.

Secondary sexual characteristics are the physical features that develop during puberty, triggered by a surge in hormones like oestrogen. These include the development of breasts, the growth of pubic and underarm hair, and the widening of the hips, which signal that the body is maturing toward reproductive readiness.

Secondary sexual characteristics are the physical traits that emerge during puberty due to rising levels of testosterone. These include the deepening of the voice, the growth of facial and body hair, increased muscle mass, and the broadening of the shoulders.

A strategy where you time sexual activity to match your fertile window and ovulation to ensure the best chance of natural conception. However, recent clinical guidance⁵ recommends having sex every 2 to 3 days during the cycle, opposed to just during the fertile window, as this is more effective at improving the chances of conception.

Anti-Müllerian hormone (AMH) is produced by little fluid-filled sacs on your ovaries that hold your eggs. These are called ‘follicles’. AMH levels are a good indicator of your ovarian reserve, which is the number of eggs you have left. It can also help us understand if you have polycystic ovaries or if you are approaching menopause, when AMH levels naturally become very low.

A group of sex hormones (including testosterone and DHEAS) that support libido and bone strength. When levels are too high, as in PMOS (formerly PCOS), they can disrupt your menstrual cycle and cause characteristic symptoms like excess body hair growth, hair thinning or acne.

A biomarker is a biological clue found in your blood, tissues, or fluids, which is essential for diagnosis, treatment monitoring, and risk assessment. It offers insights and reveals health patterns or risks that symptoms alone may not make obvious.

DHEAS is another type of hormone called an androgen. It's a form of a hormone called DHEA, which is mainly produced by your adrenal glands. Your body can then convert DHEAS into testosterone. Having too many androgens like DHEAS can lead to symptoms such as acne and excessive hair growth, which are often seen in women with PMOS (formerly PCOS).

In the first part of your menstrual cycle, when levels of oestradiol (E2) are low, your brain gets the signal to produce follicle-stimulating hormone (FSH). FSH's job is to encourage an egg in your ovary to grow and mature. Significantly high levels of FSH can sometimes indicate that you've reached menopause. This happens because your ovaries are no longer regularly releasing eggs, so your brain produces more and more FSH in an attempt to stimulate them.

Gonadotrophin-releasing hormone (GnRH) is a crucial hormone produced by the hypothalamus that acts as the master switch for your entire reproductive system. It is released in specific pulses to signal the pituitary gland to produce other key hormones like FSH and LH which then control the function of the ovaries or testes. If these pulses are disrupted or absent, it can lead to symptoms such as irregular periods, low libido, and difficulties with fertility.

Glycated haemoglobin (HbA1c) is a form of haemoglobin in your red blood cells that has sugar attached to it, making it a vital biomarker for tracking your health. Because red blood cells live for about three months, this test provides a reliable "snapshot" of your average blood sugar levels over the past 2-3 months. High HbA1c levels act as a key indicator for insulin resistance, prediabetes, or diabetes, showing that your body is struggling to manage sugar effectively.

HCG is a hormone produced after a fertilised egg implants into the uterus. Because HCG rises rapidly in the first trimester, it is the marker used by pregnancy tests to confirm you’ve conceived.

Hormones are the body’s chemical messengers produced by glands and transported by the bloodstream to various organs to regulate how they function. Hormones impact how you feel, your skin, your sleep, and your fertility.

Luteinising hormone (LH) is made in your brain. Its primary role is to trigger ovulation, which is the release of an egg from your ovary, usually around the middle of your menstrual cycle. If your LH levels are too low or stay consistently high, it can interfere with ovulation, potentially causing irregular periods or even stopping them entirely.

Oestradiol (E2) is a hormone mainly produced by your ovaries. Its levels naturally rise in the first half of your menstrual cycle, triggered by another hormone called follicle-stimulating hormone (FSH), and then decrease towards the end of your cycle, which signals to your brain that more FSH is needed. When you reach menopause, your ovaries produce very little oestradiol, which leads to a significant increase in FSH production.

Oestrogen is a hormone family including oestradiol that regulates the menstrual cycle, bone strength, mood, skin, amongst other things. Too much or too little can affect cycle regularity and fertility. Levels naturally decline during perimenopause and menopause, leading to menopause symptoms like night sweats and brain fog.

A pro-hormone acts as a building block that the body converts into active hormones.

Prolactin is a hormone that has an interesting effect on your reproductive hormones, FSH and LH, which are made in the brain. If your prolactin levels are too high, it can interfere with the normal production of FSH and LH. This disruption can then affect your menstrual cycle and potentially prevent ovulation from happening regularly.

Sex hormone-binding globulin (SHBG) is a protein in your blood that attaches itself to sex hormones like oestradiol and testosterone. Measuring your SHBG levels helps us get a clearer picture of how much of these hormones are actually available and active in your body, rather than being bound to the SHBG. By testing these hormones alongside SHBG rather than in isolation, it gives us a more accurate understanding of how these hormones might be affecting your body and can be important in diagnosing certain conditions.

Free thyroxine (FT4) is essentially the active form of the thyroid hormone thyroxine (T4), which is produced by your thyroid gland. Measuring FT4 is important because it's the part of T4 that's available for your body to use. If your FT4 levels are low, even if your total T4 seems normal, it could indicate an underactive thyroid, also known as hypothyroidism. On the other hand, high FT4 levels usually suggest an overactive thyroid, or hyperthyroidism

Testosterone is a type of hormone called an androgen, and it's also known as a sex hormone. It's produced in several parts of your body, including your ovaries and adrenal glands. If you have too much testosterone, it can lead to symptoms like acne and can also disrupt your menstrual cycle by preventing ovulation. Elevated testosterone levels are also a key factor in diagnosing PMOS (formerly PCOS).

Testosterone is the primary sex hormone in men and is essential for producing sperm and maintaining a healthy sex drive. It also plays a vital role in overall health by supporting bone density, muscle strength, and the production of red blood cells.

Thyroid-stimulating hormone (TSH) is made in the brain and acts as a messenger to your thyroid gland. It tells your thyroid to produce another hormone called thyroxine (T4). Once produced, T4 is converted into a different thyroid hormone that your body can use. If your thyroid is producing too much T4 (overactive thyroid), your brain will respond by making less TSH. On the other hand, if your thyroid isn't producing enough T4 (underactive thyroid), your brain will release more TSH to try and encourage it to work harder and increase T4 levels.

Vitamin d is necessary for regulating how much calcium is used by your body and therefore plays a crucial role in keeping your bones and teeth healthy. Having low vitamin d levels can increase your risk of bone fractures. The risk of vitamin d deficiency is higher if you have limited sun exposure, darker skin, or are menopausal. Recent studies have also linked PMOS (formerly PCOS) to low vitamin d levels, making those with PMOS (formerly PCOS) more susceptible.

Adenomyosis occurs when tissue similar to the uterine lining grows into the muscular wall of the uterus, leading to heavy, painful periods and pelvic pain.

Adhesions are bands of scar tissue that can cause organs or tissues to stick together. In reproductive health, these often form as a result of inflammation from conditions like endometriosis or infections, pelvic inflammatory disease / PID or surgery. These sticky bands can alter your pelvic anatomy, sometimes affecting the fallopian tubes and impacting fertility or causing chronic pelvic pain.

Amenorrhoea is the clinical term for absent periods and is often a protective response to high stress, extreme exercise, or insufficient nutrition, though it can also stem from underlying health conditions like PMOS (formerly PCOS).⁶ Primary amenorrhoea refers to the absence of menstruation by age 15, or age 13 if secondary sexual characters are not yet present. Secondary amenorrhoea is the absence of periods for over 3 months in those with previously regular cycles, or 6 months for irregular cycles, and affects roughly 2 to 5% of people of reproductive age.⁷

Asherman’s syndrome is scar tissue (adhesions) inside the uterus that can cause the uterine walls to stick together, often due to uterine surgeries like dilation and curettage (D&C) or infections. It can make periods light or absent and may also create challenges for pregnancy to occur or lead to (recurring) miscarriages.

Clinical depression is a mental health condition characterised by at least two weeks of persistent low mood, loss of interest in activities, and low self-esteem. It impacts daily life through fatigue, sleep changes, and reduced concentration.

Diabetes is a chronic condition where the body cannot effectively regulate blood sugar levels. Left unmanaged, it can cause hormonal imbalance, disrupt ovulation, and increase the risk of complications during pregnancy.

Early menopause is when your period stops for good before the age of 45, meaning your ovaries have stopped releasing eggs earlier than expected. This premature loss of ovarian function can be driven by genetic factors, autoimmune diseases, or medical interventions such as chemotherapy, radiotherapy, and surgery. This leads to hormonal shifts like permanent drops in oestrogen, often resulting in menopause symptoms like hot flushes, mood changes, vaginal dryness, and increased risks to bone health.

Ectopic pregnancy occurs when an embryo (fertilised egg) implants and grows outside the main cavity of the uterus, most commonly within a fallopian tube. Because these areas are not designed to hold a growing embryo, the pregnancy cannot proceed normally. This can lead to symptoms like sharp abdominal pain, vaginal bleeding, and shoulder tip pain. This condition requires immediate medical intervention through monitoring, medication or surgery to prevent life-threatening internal bleeding if the tube ruptures.

An endometrioma is a type of cyst that forms on the ovaries when endometriosis tissue grows deep within the ovarian tissue. These are often called "chocolate cysts" because they are filled with dark, old blood that has collected over multiple menstrual cycles. Their presence can impact ovarian reserve and is often a sign of more advanced or deep endometriosis within the pelvis.

Endometriosis is a chronic condition affecting 1 in 10 women in the UK⁸ and those assigned female at birth. It occurs when tissue similar to the uterine lining grows outside of the uterus, most commonly in the pelvic area. This tissue can be superficial or deeply infiltrating, appearing on the ovaries as endometriomas, or on the bladder, bowel, and pelvic ligaments. Because this tissue bleeds and breaks down during your cycle with nowhere to go, it causes intense inflammation, fatigue, and pelvic pain that can significantly impact your reproductive health.

Fibroids are benign, non-cancerous growths of muscle and tissue that develop in or around the uterus. In some cases where fibroids are large, they can interfere with fertility by blocking fertilisation or the implantation of a fertilised egg. Most fibroids do not cause symptoms, however some are associated with heavy painful periods, pelvic pain, depending on their location and size.

Galactorrhoea is a condition where a milky discharge leaks from the breasts which is unrelated to breastfeeding or pregnancy. It is usually caused by an excess of the hormone prolactin, which can be triggered by certain medications, underlying health conditions, or issues with the pituitary gland.

Hirsutism is a symptom where women or those assigned female at birth grow dark, thick hair in areas where it is more typical for men, such as the face, chest, or back. This is usually caused by an excess of androgens and is a common symptom of conditions like PMOS (formerly PCOS).

Hormonal acne causes deep breakouts, usually around the jaw, chin, and lower cheeks. It is driven by normal hormonal fluctuations during the cycle, or in some cases due to high androgens telling the skin to produce more oil, as seen in PMOS (formerly PCOS).

Having consistently high levels of prolactin, which can interfere with the signals for ovulation and cause irregular periods or for them to stop all together. High PRL symptoms include irregular or absent periods, unexplained breast milk production (galactorrhoea), infertility, and vaginal dryness.

Hyperthyroidism refers to an overactive thyroid, meaning the thyroid gland is producing too many hormones. Because the thyroid regulates metabolism, heart rate, temperature and muscle function, high hormone levels can cause symptoms such as anxiety, heart palpitations and unintended weight loss.

If untreated, hyperthyroidism can affect your long term health and fertility.

Hypothalamic amenorrhoea (HA) is a condition where periods stop completely due to a dysfunction of the hypothalamic-pituitary-ovarian (HPO) axis. It occurs when the hypothalamus stops releasing gonadotrophin-releasing hormone (GnRH). It can be triggered by several factors, including weight loss, low energy availability due to exercise, stress, or chronic illness.

HA is reversible with the right support and treatment.

Hypothyroidism refers to an underactive thyroid, which means the thyroid gland is not producing enough thyroid hormones. Because the thyroid helps regulate metabolism, heart rate, temperature and muscle function, low hormone levels can lead to symptoms such as fatigue and weight gain.

If untreated, hypothyroidism may worsen over time and can affect long term health and fertility.

An incomplete miscarriage occurs when some pregnancy tissue has passed from the uterus, but some remains inside the body. Common symptoms include heavy or prolonged vaginal bleeding, intense abdominal cramping, and the passing of large blood clots. This condition requires medical evaluation to ensure the uterus is fully cleared, which may involve waiting for the tissue to pass naturally, using medication, or undergoing a minor surgical procedure.

Iron deficiency anaemia happens when there is not enough iron available for your body to make healthy red blood cells. People can be iron deficient before they become anaemic, and many iron deficient people will not yet show anaemia on a blood count. It is very common among people who menstruate and among those who do not get enough iron through their diet. When iron levels are low, your body cannot produce enough red blood cells, which affects how well oxygen is carried around the body and can leave you feeling consistently tired or low in energy.

Menopause refers to when menstrual cycles stop permanently. The ovaries no longer release eggs and produce only very low levels of hormones oestrogen and progesterone. This causes symptoms like vaginal dryness, low libido, brain fog, and disrupted sleep patterns. Diagnosis is made after 12 months without periods in someone over 45, or earlier if due to surgery or medical treatment. The average age is 51, though it occurs for most between 45 and 55⁹.

Menopause symptoms include physical and mental changes like hot flushes, night sweats, and brain fog caused by declining levels of hormones (particularly oestrogen). Symptoms can start occurring during perimenopause.

Miscarriage is the loss of a pregnancy before the 24th week, often occurring because the embryo or foetus does not develop as it should. Common symptoms include vaginal bleeding, cramping or pain in your lower abdomen, and a sudden end to pregnancy symptoms like morning sickness or breast tenderness. While it is a deeply emotional experience, most miscarriages are one-off events caused by chromosomal issues and are not related to anything the individual did or did not do.

A molar pregnancy occurs when an imbalance in genetic material during fertilisation causes abnormal cells to grow in the uterus instead of a healthy foetus. Symptoms often include dark brown to bright red vaginal bleeding and severe nausea and vomiting. Because this tissue can grow rapidly, it requires medical removal through a procedure like suction aspiration (using vacuum pressure to remove uterine contents) to prevent complications or the development of rare persistent growths.

Ovarian cysts are fluid-filled sacs that develop on or inside an ovary, which are very common and often a natural part of your menstrual cycle. While most cysts are "functional" and disappear on their own without treatment, others, like endometriomas or those caused by PMOS (formerly PCOS), may require monitoring if they cause pelvic pain or impact your fertility.

PCOS (Polycystic Ovary Syndrome) is a common condition that affects at least 1 in 10 women of reproductive age. When it happens, the body makes hormones in different amounts than expected, which can influence ovulation, periods, skin and hair, and overall metabolic health. People experience PCOS in very different ways and symptoms can range from mild to more noticeable changes. Although it can sometimes affect how regularly you ovulate, many people with PCOS do go on to conceive naturally or with simple support.

*Note: PCOS was officially renamed PMOS (Polyendocrine Metabolic Ovarian Syndrome) in May 2026. If you've seen this term, see PMOS.*

PMOS (Polyendocrine Metabolic Ovarian Syndrome) is the updated name for the condition previously known as PCOS. PMOS is characterised by fluctuations in hormones, with impacts on weight, metabolic and mental health, skin, and the reproductive system. The name was changed because the old term "polycystic ovary" reduced a complex, long-term hormonal condition to a misunderstanding about cysts, contributing to missed diagnoses and inadequate treatment. The diagnostic criteria have not changed, so a PCOS diagnosis is equivalent to PMOS.

Perimenopause is the transition phase leading up to menopause when your hormone levels begin to fluctuate and drop. These hormonal shifts can lead to changes in the menstrual cycle, including irregular periods, and symptoms such as hot flashes, night sweats, changes in mood or sleep, and vaginal dryness.The average start age in the uk is around 47.¹¹ Symptoms are linked to lowering oestrogen.

PID is an infection of the reproductive tract including the uterus, fallopian tubes, and ovaries, usually caused by untreated sexually transmitted infections. If untreated, it can cause scarring, chronic pain, and may impact future fertility by causing tubal blockages and can also increase the risk of ectopic pregnancy.

Premenstrual Dysphoric Disorder PMDD is a severe, chronic, and often debilitating form of PMS causing intense emotional (depression, anxiety, rage) and physical symptoms in the 1-2 weeks before menstruation (luteal phase). It affects 3-8% of women¹², and symptoms typically disappear within a few days of bleeding.

PMS (premenstrual syndrome) refers to the physical and emotional changes many people experience in the days leading up to their period. Main symptoms include mood swings, irritability, anxiety, fatigue, breast tenderness, bloating, and food cravings. These are triggered by the natural rise and fall of hormones like progesterone and oestrogen during the luteal phase.

POI occurs when the ovaries stop functioning as expected before the age of 40.¹³ This means they may release lower amounts of hormones such as oestradiol, and may not release eggs regularly due to a lower egg reserve. POI can happen for many different reasons, including genetic or autoimmune factors, or as a result of certain treatments, though sometimes no clear cause is found.

Polycystic ovaries (PCO), also known as PCOM, describes how ovaries look on an ultrasound when they contain a higher-than-average number of small follicles. This is a common finding and does not mean the presence of the hormonal condition PMOS (formerly PCOS) unless it’s accompanied by symptoms. Many people have this ovarian morphology while maintaining regular menstrual cycles and perfectly balanced hormone levels.

A polyp is a small, non-cancerous growth on the uterine lining that can cause spotting or heavy bleeding. Polyps, depending on their size and location, can sometimes result in problems with fertility (female) as they may block fertilisation or the implantation of a fertilised egg.

Von Willebrand disease is caused by a deficiency of a protein needed to clot blood properly. This can lead to excessive bleeding during the menstrual cycle, and therefore causes heavy and prolonged bleeding.

Abortion is a medical procedure or treatment used to end a pregnancy so that it does not result in a birth. Medical abortion involves taking two types of medication that induce contractions to empty the uterus, effectively ending a pregnancy without surgery. A surgical abortion is a procedure where a doctor removes the pregnancy from the uterus, typically using suction (vacuum aspiration) or, in later stages, specialised instruments (dilation and evacuation).

An AFC (Antral Follicle Count) is a non-invasive, transvaginal ultrasound scan that counts the number of small, fluid-filled follicles in the ovaries. Conducted during the early follicular phase, it acts as a key indicator of a woman's ovarian reserve (egg quantity) to estimate fertility potential and predict responses to IVF stimulation.

An AMH test is a blood test used to measure levels of anti Müllerian hormone (AMH) to estimate current egg quantity (not quality). Unlike many other reproductive hormones, an AMH test can be taken at any point in the menstrual cycle because levels do not fluctuate significantly month to month. This makes it a vital tool for identifying a declining reserve, assessing potential response to fertility treatments, or detecting high follicle counts often associated with PMOS (formerly PCOS).

Egg freezing is a medical procedure where eggs are retrieved from the ovaries and frozen to help preserve a person’s future fertility options. The process involves several days of hormone injections before the eggs are collected under sedation. While this method increases the chance of a successful pregnancy later in life, it does not guarantee a birth because the success depends heavily on the age and health of the eggs at the time of freezing.

This is a fertility preservation technique where an egg is fertilised with sperm in a lab to create an embryo, which is then frozen for future use.

Fertility testing involves blood tests and scans used to check your hormone levels and your reproductive health. These results help you understand your egg reserve, whether you are ovulating, and if there are any underlying issues affecting your chances of getting pregnant.

Haemolysis occurs when red blood cells in a sample burst or break down, which can dilute the blood and lead to inaccurate lab results. Because these damaged cells release their contents into the surrounding fluid, labs will typically reject the sample and request a new one to ensure the data is reliable. It is the most common reason for sample rejection and can happen during collection or transport, regardless of whether it was an at-home finger prick or done professionally.

HRT relieves menopause symptoms by replacing declining oestrogen / estrogen and progesterone.

ICSI is a specialised form of IVF where a single sperm is injected directly into an egg. It’s often used for male-factor infertility or when using previously frozen eggs.

Intrauterine insemination involves placing prepared sperm directly into the uterus around ovulation, making it easier for the sperm to reach the egg.

In vitro fertilisation is when eggs and sperm are combined in a lab to create embryos, which are then transferred to the uterus. It is a highly effective treatment for many fertility challenges.

Oophorectomy is the surgical removal of one or both ovaries. Removing both causes immediate menopause.

A keyhole surgical procedure for people with PMOS (formerly PCOS) that uses heat to make tiny holes in the ovary. It is intended to lower androgens and help your body return to a regular ovulation pattern. While it can trigger a hormonal shift, there is currently limited evidence backing its long-term benefits compared to other fertility treatments.

This refers to the process of tracking how your egg quantity changes over time using a combination of AMH testing and AFC. It is recommended to repeat AMH testing every 6 to 12 months to identify trends and guide decisions around family planning, fertility preservation and treatment timing and do it in combination with an AFC for the most comprehensive picture of your ovarian reserve.

Ovulation induction involves using medication (like letrozole) to encourage the ovaries to release an egg. It’s a commont reatment for people with PMOS (formerly PCOS) or irregular cycles.

A pelvic ultrasound scan uses sound waves to create real-time images of your womb, ovaries and uterine lining. For the most accurate results, it's carried out transvaginally using a slim, specialised probe. A transvaginal ultrasound is a straightforward, quick procedure done by expert sonographers in a comfortable clinic setting and is the most accurate way to check your follicles (AFC), uterine lining, and screen for things like fibroids or PCOM.

Telemedicine is the practice of caring for patients remotely when the provider and the patient are not physically present with each other. This is typically done through secure video calls, phone consultations, or online messaging, allowing you to receive medical advice, diagnoses, and prescriptions from your own home. It has become a vital tool in modern healthcare for increasing accessibility, especially for routine check-ups, mental health support, and the management of long-term conditions.

A transabdominal ultrasound is a non-invasive imaging test used to visualise the reproductive organs (uterus, ovaries, fallopian tubes) by moving a probe over the lower abdomen. It is considered less accurate than a transvaginal ultrasound, and typically requires a full bladder for a clearer view.

A baseline is the initial measurement taken at a “resting” or starting point to serve as the standard that all your future results are compared against. In a fertility test, this is typically done on day 3 of your cycle for consistent comparison and because your hormones are at their lowest and most stable levels before the body begins preparing for ovulation.

A lipid profile is a group of tests measuring fats, including cholesterol and triglycerides, in your blood to assess overall metabolic and heart health. Your lipid profile provides a useful indicator of your risk of cardiovascular disease, which is more common in people with PMOS (formerly PCOS) and those who have gone through menopause.

A reference population is a defined group used as a standard or benchmark for comparing someone's results against. It usually consists of a broad population of others of the same age.

A reference range is a range of values used to help us to interpret your hormone results. As not all of us are exactly the same, we won’t all have the same hormone levels. In other words, a healthy hormone range varies because people vary. The reference range is usually based on the range of values/results that 95% of a healthy population fall into.

Sensitivity is how good a test is at spotting people who actually have a condition. A highly sensitive test is reliable because it rarely misses a positive result or gives a “false negative” (when a test result indicates that a condition is absent when it is actually present). However, a high sensitivity may have a high false positive proportion and thus a good test requires both a high sensitivity and high specificity.

Specificity is how good a test is at correctly identifying people who do not have a condition. This ensures that healthy people aren't wrongly told they have an issue, which reduces the chance of a “false alarm.” However, a high sensitivity may have a high false negative proportion and thus a good test requires both a high sensitivity and high specificity.