Fertility glossary

The words you'll meet in reports and clinic appointments, explained in plain language. Each one links to a guide that goes further.

These definitions are awaiting medical review and are not final.

A

AMH (anti-Müllerian hormone): A hormone made by the small follicles in the ovaries, measured with a blood test. It gives a rough idea of how many eggs are left (ovarian reserve). It does not tell you about egg quality or whether you can get pregnant naturally. Read the guide →
Antral follicle count (AFC): A count of the small fluid-filled sacs (follicles) seen in both ovaries during a vaginal ultrasound, usually early in the period. Like AMH, it helps estimate ovarian reserve and plan treatment. Read the guide →
Azoospermia: When no sperm are found in a semen sample. It can happen because sperm are not being made, or because they are made but blocked from coming out. The test is usually repeated, and further checks help find the cause and options. Read the guide →

B

Blastocyst: An embryo that has grown in the lab for about five or six days after fertilisation. By this stage it has an outer layer that may form the placenta and an inner group of cells that may form the baby. Read the guide →

C

Cervical mucus: Fluid made by the cervix (the neck of the womb) that changes through the cycle. Around ovulation it often becomes clear, slippery and stretchy, like raw egg white, which helps sperm move through. Read the guide →
Cryopreservation (freezing): Freezing eggs, sperm or embryos at very low temperatures so they can be stored and used later. Most clinics now use vitrification, a very fast freezing method. Read the guide →

E

Ectopic pregnancy: A pregnancy that starts growing outside the womb, most often in a fallopian tube. It cannot continue and needs urgent medical care. Severe tummy pain, shoulder-tip pain, fainting or heavy bleeding in early pregnancy are emergency signs. Read the guide →
Egg collection (egg retrieval): The IVF step where eggs are taken from the ovaries with a thin needle guided by ultrasound. It is done under sedation and usually takes a short time. Read the guide →
Embryo: The early stage of development after an egg is fertilised by a sperm. In IVF, embryos grow in the lab for a few days before one is transferred to the womb or frozen. Read the guide →
Embryo transfer: The step in IVF where an embryo is gently placed inside the womb through a thin, soft tube passed through the cervix. It usually feels like a smear test and does not need anaesthesia. Read the guide →
Endometriosis: A condition where tissue similar to the lining of the womb grows outside the womb, such as on the ovaries or in the pelvis. It can cause painful periods, pain during sex and difficulty getting pregnant, though many people with it do conceive. Read the guide →
Endometrium: The inner lining of the womb. It thickens each cycle to get ready for an embryo to implant, and is shed as a period if pregnancy does not happen. Read the guide →

F

Fallopian tubes: Two thin tubes that connect the ovaries to the womb. The egg and sperm usually meet inside a tube, so blocked or damaged tubes can make natural pregnancy harder. Read the guide →
Fertile window: The few days in each cycle when sex is most likely to lead to pregnancy. It covers the days before ovulation and the day of ovulation, because sperm can survive for several days while an egg lives for about a day. Read the guide →
Fibroids: Non-cancerous growths of muscle in or on the wall of the womb. They are common and often cause no problems, but depending on their size and position some can affect periods or fertility. Read the guide →
Frozen embryo transfer (FET): Thawing an embryo that was frozen earlier and placing it in the womb, in a later cycle. It lets people use extra embryos from one IVF cycle without another egg collection. Read the guide →
FSH (follicle-stimulating hormone): A hormone from the pituitary gland in the brain that helps eggs grow in the ovaries and helps make sperm in the testes. It is often checked with a blood test early in the menstrual cycle. Read the guide →

H

HSG (hysterosalpingogram): An X-ray test where a dye is passed through the cervix to show the shape of the womb and whether the fallopian tubes are open. It is usually done after a period ends and before ovulation. Read the guide →
Hydrosalpinx: A fallopian tube that is blocked at the far end and has filled with fluid. Doctors usually discuss treating it before IVF, because the fluid can make it harder for an embryo to implant. Read the guide →
Hysteroscopy: A procedure where a thin camera is passed through the cervix to look inside the womb. It can find and often remove problems such as polyps, some fibroids or scar tissue. Read the guide →

I

ICSI (intracytoplasmic sperm injection): A lab technique used during IVF where a single sperm is injected directly into each egg. It is mainly used when there are sperm problems or when eggs did not fertilise in an earlier cycle. Read the guide →
Infertility: Not getting pregnant after a year of regular sex without contraception, or after six months if you are 35 or older. It is a medical condition that can involve either partner, and it does not mean pregnancy is impossible. Read the guide →
IUI (intrauterine insemination): A treatment where washed, concentrated sperm are placed directly into the womb with a thin tube around the time of ovulation. It is simpler than IVF and may be done with or without ovulation medicines. Read the guide →
IVF (in vitro fertilisation): A treatment where eggs are collected from the ovaries and fertilised with sperm in a lab. One embryo is then placed in the womb, and any suitable extra embryos can be frozen for later. Read the guide →

L

Laparoscopy: Keyhole surgery under general anaesthesia, where a thin camera is passed through a small cut near the navel to look at the womb, tubes and ovaries. It can diagnose and treat conditions such as endometriosis. Read the guide →
Letrozole: A tablet often used to help the ovaries release an egg, especially in people with PCOS. It should only be taken under a doctor's guidance, with monitoring. Read the guide →
LH (luteinising hormone): A hormone from the pituitary gland. A sudden rise, called the LH surge, triggers ovulation, which is what home ovulation kits detect. It also helps the testes make testosterone. Read the guide →
Luteal phase: The second part of the menstrual cycle, from ovulation until the next period. During this time the body makes progesterone to prepare the womb lining for a possible pregnancy. Read the guide →

M

Miscarriage (pregnancy loss): When a pregnancy ends on its own before the baby can survive outside the womb. The medical term is "spontaneous abortion". Most early losses are caused by chance chromosome problems and are not caused by anything the person did. Read the guide →
Morphology (sperm): The size and shape of sperm, as seen in a semen analysis. It is normal for most sperm in a sample to look imperfect, so this result is always read alongside count and movement. Read the guide →
Motility (sperm): How well sperm move, measured in a semen analysis. Progressive motility means sperm swimming forward, which they need to do to reach the egg. Read the guide →

O

OHSS (ovarian hyperstimulation syndrome): A reaction to fertility medicines where the ovaries swell and fluid can leak into the tummy. Most cases are mild, but severe tummy pain, breathlessness or passing very little urine need urgent care. Read the guide →
Oligospermia (low sperm count): When a semen sample has fewer sperm than the usual reference range. Sperm counts vary from test to test, so a low result is usually repeated before drawing conclusions. Read the guide →
Ovarian reserve: A way of describing how many eggs are left in the ovaries. It naturally falls with age and is estimated with AMH and antral follicle count. It says little about egg quality. Read the guide →
Ovulation: When an ovary releases a mature egg, usually once in each cycle. In a regular cycle this tends to happen about two weeks before the next period. Read the guide →
Ovulation induction: Treatment with medicines, such as tablets or injections, to help the ovaries release an egg in people who do not ovulate regularly. It is monitored to check how the ovaries respond and lower the chance of twins. Read the guide →

P

PCOS (polycystic ovary syndrome): A common hormonal condition that can cause irregular or missed periods, signs of higher male-type hormones such as extra hair or acne, and many small follicles on the ovaries. It is a frequent cause of irregular ovulation and is often treatable. Read the guide →
PGT-A (preimplantation genetic testing for aneuploidy): Testing a few cells from an IVF embryo to check whether it has the usual number of chromosomes. It is an optional add-on, and the evidence on whether it helps most people is mixed. Under India's PCPNDT Act it must never be used to choose or reveal sex. Read the guide →
Polyps (endometrial polyps): Small, usually non-cancerous growths on the lining of the womb. They may cause irregular bleeding and can sometimes affect implantation. They can usually be removed during a hysteroscopy. Read the guide →
Primary infertility: Infertility in a person or couple who have never had a pregnancy before. Read the guide →
Progesterone: A hormone made after ovulation that prepares the womb lining for an embryo and supports early pregnancy. A blood test about a week before an expected period can show whether ovulation has happened. Read the guide →
Prolactin: A hormone from the pituitary gland that helps make breast milk. High levels outside pregnancy and breastfeeding can disturb ovulation and periods, and are often treatable. Read the guide →

R

Recurrent pregnancy loss: When a person has had two or more pregnancy losses. Doctors may suggest tests to look for a cause, although often no single cause is found, and many people go on to have a pregnancy that continues. Read the guide →

S

Secondary infertility: Difficulty getting pregnant after having been pregnant before, whether or not that pregnancy led to a birth. It is common and deserves the same care as primary infertility. Read the guide →
Semen analysis: A lab test of a semen sample that checks the amount of semen and the number, movement and shape of sperm. It is one of the first and simplest fertility tests, and results are compared with WHO reference values. Read the guide →
Sperm count: The number of sperm in a semen sample, given as the concentration per millilitre and the total in the sample. It can change from one sample to the next, so one result is not the whole picture. Read the guide →

T

TSH (thyroid-stimulating hormone): A hormone from the pituitary gland that controls the thyroid. A TSH blood test checks for an underactive or overactive thyroid, which can affect periods, ovulation and pregnancy. Read the guide →
Two-week wait: The time between ovulation, IUI or embryo transfer and when a pregnancy test can give a reliable result. Many people find it emotionally hard, and it is normal to feel anxious. Read the guide →

U

Unexplained infertility: When the standard fertility tests for both partners come back normal but pregnancy has not happened. It means no cause was found with today's tests, not that nothing can be done. Read the guide →

V

Varicocele: Swollen veins in the scrotum, similar to varicose veins in the legs. They are common and often cause no problems, but in some men they are linked with lower sperm quality. Read the guide →