Abortion: Spontaneous or induced termination of pregnancy.

Acrosome: A small "cap" overlaying the head of a sperm.

Acrosome reaction: The loss of the acrosome necessary for successful fertilisation.

Adhesion: The sticking of ovaries, tubes, uterus, bowel and abdominal lining to one another. Adhesions affects the normal movement of these organs and can cause infertility. They can be due to pelvic surgery, tubal infections or endometriosis.

AI: Artificial insemination

Amenorrhoea: Absence of periods, usually taken as fewer than 2 periods per year

Amniocentesis: A test where amniotic fluid is aspirated to test the foetus for chromosomal abnormalities.

Androgens: Male sex hormones

Anovulation: The absence of ovulation.

Antibodies: Chemicals produced by the body to fight or attack foreign substances entering the body. Normally they prevent infection. When they attack the sperm or foetus, however, they cause infertility. Sperm antibodies may be made by either the man or the woman.

ART: Assisted Reproductive Technology, includes all types of infertility treatment that involves medical intervention such as donor sperm insemination, ovulation induction, IVF, GIFT, ICSI etc.

Azoospermia: The absence of sperm in the ejaculate.

Basal body temperature: Body temperature taken orally, upon waking in the morning before any activity.

Blastocyst: A stage in the development of the early human embryo. The blastocyst forms four days after fertilisation and is a sphere of cells containing a fluid-filled cavity.

Blastomere: One of the cells in an early embryo.

Cervical mucus: Mucus produced by the cervix which permits passage of sperm to the uterus and fallopian tubes. This mucus changes in volume and quality at the time of ovulation.

Cervix: Lower section of the uterus that protrudes into the vagina.

Conception: Fertilisation of a woman's egg by a man's sperm.

Chorion villus sampling (CVS): A procedure where cells are taken a pregnancy at about 10 weeks to assess the normality of the chromosomes.

Chromosome: A thread-like structure of DNA which makes up all the genes. A normal human body cell has 46 chromosomes whereas eggs and sperm have 23.

Cleavage arrest: The failure of an embryo to continue through to the next stage of development during cleavage.

Clomiphene: A drug used to stimulate the ovaries to produce follicles.

Congenital: Existing before birth.

Cryopreservation: Storage by freezing, used for embryos and eggs.

Cytogenetics: The study of the chromosomes.

DI (Donor Insemination): Insemination of a woman using donor sperm.

Dispermy: The fertilisation of an egg by two sperm instead of one as normally occurs.

Donor eggs: Eggs taken from one woman and donated to another for pregnancy.

Ectopic pregnancy: A pregnancy that implants outside the uterus for example in the Fallopian tube.

Ejaculate: Semen ejected from the penis during orgasm.

Embryo: The fertilised egg and the subsequent stages of early human development.

Embryo biopsy: The removal of one or two cells from an early embryo for diagnosing chromosomal or genetic abnormalities.

Embryo transfer (ET): The placement of embryos into the uterus using a fine catheter.

Endometrium: Lining of the uterus or womb.

Endometriosis: The presence of endometrial tissue (the normal uterine lining) in abnormal locations such as the Fallopian tubes, the ovaries and the peritoneal cavity.

Epididymis: A cord-like structure in the testes where sperm are stored.

Fallopian tubes: Pair of narrow tubes that carry the ovum (egg) from the ovary to the uterus.

Fertilisation: Penetration of the egg by the sperm and joining of genetic materials to result in the development of an embryo.

Fibroid: A benign tumor of fibrous tissue in the uterus, may contribute to infertility.

Folic Acid: Folic Acid is a vitamin supplement which women are recommended to take before conceiving and in early pregnancy as it reduces the risk of neural tube defects in the foetus (spina bifida).

Foetus: The developing human from the end of the eighth week of development from fertilisation (when all major structures have begun to develop) until birth.

Follicle Stimulating Hormone (FSH): Hormone produced in the pituitary gland that stimulates the ovary to develop a follicle for ovulation in women and sperm production in men.

Follicle: A fluid-filled sac in the ovary which contains an egg that is released at ovulation. In healthy women, each month an egg develops inside this follicle.

Follicular phase: First half of the menstrual cycle when ovarian follicle development takes place and the egg matures.

Gamete: A reproductive cell, either sperm or egg.

Gamete Intra Fallopian Transfer (GIFT): The mixing of sperm and egg outside the body and the transfer of the mixture to the Fallopian tube, usually by laparoscopy.

Gonadotrophin: A hormone that stimulates the production of sperm or eggs.

Home Pregnancy test: A test a woman can use at home to test urine for the presence of human Chorionic Gonadotropin (hCG).

Hormone: A chemical substance which has a specific regulatory effect on the activity of a particular organ.

Human Chorionic Gonadotrophin (hCG): The hormone produced in early pregnancy which keeps the corpus luteum producing progesterone.

Hyperstimulation see OHSS

ICSI - see Intracytoplasmic Sperm Injection

Idiopathic: When the couple is diagnosed as having "Idiopathic infertility" this means unexplained, ie none of the tests in the infertility investigation is abnormal and a cause has not been determined.

Implantation: When the embryo attaches and embeds in the endometrium. Begins about seven days after fertilisation and is complete about 14 days after fertilisation.

Impotence: Failure to achieve an erection.

Infertility: The inability of a couple to produce children in spite of repeated attempts.

Insemination: The bringing together of sperm and egg.

Intra-Cytoplasmic Sperm Injection (ICSI): A procedure, used for severe forms of male infertility, where a single sperm is injected into the egg.

In Vitro Fertilisation (IVF): The procedure by which eggs and sperm are mixed in the laboratory and the process of fertilisation occurs outside the body.

Laparoscopy: A surgical investigation using a telescope-like instrument to lokk at the pelvic organs, performed as part of an infertility investigation.

LH surge: The release of a large amount of Luteinising hormone (LH) from the pituitary which triggers ovulation.

Libido: Sexual desire

Luteal phase: Post-ovulatory phase of the menstrual cycle. The corpus luteum produces progesterone, which causes the uterine lining to thicken to support the implantation and growth of the embryo.

Luteinising hormone (LH): A hormone produced by the pituitary which function is to mature and trigger the release of the egg at ovulation.

Male factor: When the cause of infertility is attributed to poor sperm quality.

Menopause: The time a woman stops menstruating.

Menstruation: Shedding of the uterine lining by bleeding, which in the absence of pregnancy, normally occurs about once a month.

MESA (Micro Epidydimal Sperm Aspiration): A procedure whereby immature sperm is aspirated from the epidydimis. This is done in cases where the man has had a vasectomy or in men who are born without the vas deferens (the duct that transports sperm from the epidydimis into the ejaculate). Sperm extracted this way can only fertilize the egg if the ICSI procedure is used.

Miscarriage: Spontaneous loss of an embryo or foetus from the womb.

Mumps: Mumps is an acute viral illness and usually presents with inflammation of the salivary glands, particularly the parotid glands (salivary glands near the ears). This illness can also cause inflammation of other tissues, most frequently the covering and substance of the central nervous system (meningoencephalitis), next the pancreas (pancreatitis) and especially after adolescence, the ovary (oophoritis) and the testis (orchitis). The mature testis is particularly susceptible to damage from mumps which can lead to infertility.

Oestrogen: A female sex hormone produced by the ovaries. Oestrogen is responsible for the development of the secondary feminine sex characteristics, which include breasts, rounded hips, and pubic hair. Together with progesterone, oestrogen regulates the changes that occur with each monthly period and prepares the uterus for pregnancy.

OHSS (Ovarian Hyperstimulation Syndrome): A potentially dangerous condition caused by excessive response to fertility drugs.

Oligomenorrhoea: Infrequent periods, usually taken as 2-10 periods per year.

Oligospermia: A low sperm count.

Oocyte: The female reproductive cell (egg).

Oocyte retrieval: When mature eggs are retrieved from the ovaries using a fine needle. The procedure is done vaginally and the needle is guided by ultrasound. Follicular fluid is aspirated and the egg is identified by an embryologist using a microscope.

Ovaries: Sexual glands of the female that produce the hormones oestrogen and progesterone, and in which the eggs develop. There are two ovaries, one on each side of the pelvis.

Ovulation: Discharge of a mature egg, usually at about the midpoint of the menstrual cycle.

Ovulation induction: When fertility drugs, tablets or injections, are used to make a woman ovulate.

Ovum: The egg or reproductive cell from the ovary. This sex cell contains the female's genetic information.

PCO (Poly Cystic Ovaries): A term that describes ovaries that contain lots of little follicles.

PCOS - Poly Cystic Ovarian Syndrome: A condition characterized by a number of features such as lots of little follicles in the ovaries, excessive hair growth, infrequent or no ovulation and irregular or no periods, being overweight and abnormal hormone levels. Women with PCOS often have difficulty conceiving and have increased risk of miscarriage if they do conceive.

Pituitary gland: This gland is stimulated by the hypothalamus and controls all hormonal functions. Located at the base of the brain just below the hypothalamus, it controls many major hormonal factories throughout the body including the gonads (ovaries and testes), the adrenal glands, and the thyroid gland.

Preimplantation Genetic Diagnosis (PGD): Genetic and chromosomal analysis of a cell taken from an embryo before transfer to the uterus.

Primary infertility: This refers to a couple that has never been able to conceive.

Progesterone: Hormone secreted by the corpus luteum of the ovary after ovulation has occurred. It is responsible for preparing the uterus for pregnancy.

Puberty: Adolescence.