Entry of a sperm cell into an egg: their "marriage". The egg is activated by this event, so that: (1) "cortical granules" are expelled that stop further sperm binding to the egg; (2) the second division of meiosis is completed, with expulsion of the second polar body; and (3) the machinery of the egg is got going, which will form pronuclei of the male and female chromosomes prior to syngamy.

IVF, or fertilisation of the egg (the secondary oocyte) by a sperm (a spermatozoon) in vitro, i.e. in the laboratory. Necessary if the fallopian tubes are diseased or missing; useful if sperm fertilising capacity is doubtful, because evidence of fertilisation can be seen before the egg is transferred as an embryo.

The point at which the wide ampulla of the fallopian tube meets the narrow isthmus. The place where fertilisation of the egg by a sperm cell normally takes place.

A group of medical treatments ranging from assisted insemination (IUI) to in vitro fertilisation (IVF), including its technical variants (such as GIFT, ICSI and PGD, and with the following common characteristics: (1) they are aimed at increasing the chance of pregnancy each month, thus overcoming the medical disability of infertility; (2) there is little or no "spillover" of therapeutic effect beyond the cycle or month in which treatment is invoked; and (3) there is some form of procedural intervention, with sperm, eggs or embryos spending some time outside of the body. It's not necessary for there to be stimulation of the ovaries (superovulation) for multiple development of follicles.

An in vitro fertilisation manipulation in which a small opening is made in the zona pellucida of the early embryo to help the blastocyst emerge prior to implantation. Formerly carried out by judicious use of an enzyme to dissolve the zona (but risking damage to the embryo), leading IVF programs use a microlaser.

Stage of development of the early embryo that has undergone blastulation, in which a fluid-filled cavity forms in the formerly solid ball of cells (the morula), about 5 days after fertilisation. For the first time, a distinction can be made between a sheet of cells to one side, which will form the embryo proper, termed the inner cell mass, and the remaining, peripheral cells that constitute the trophectoderm, which -- after the blastocyst "hatches" through the zona pellucida and undergoes implantation -- will form the trophoblast. An old-fashioned term for an inevitable miscarriage, meaning that the ovum (in its classical sense for professional embryologists) has not developed normally after fertilisation, there being present just the supporting tissues and no embryo. The term is descriptive, it has no diagnostic value as to the cause of the miscarriage.

A GnRH-antagonist made by Serono. Approved for women undergoing in vitro fertilisation), with good results when started on day 7 of the cycle, after 5 or 6 days' Gonal-F in suppressing the LH surge; the dosage, however, appears to be critical, to avoid over-suppressing natural luteinising hormone. Marketed as Cetrotide.

The act of becoming pregnant. Traditionally, the fertilisation of the egg (the oocyte) by a sperm (the spermatozoon) and the beginning of the growth of the embryo [Butterworths Medical Dictionary]. Since the advent of in vitro fertilisation, conception is said to have occurred only if the conceptus has undergone successful implantation, as evidenced by a positive pregnancy test. See also conception rate and pregnancy.

The product of conception from fertilisation.

Congenital (present from birth) absence of the two vasa deferentia, which conduct sperm from the testes to the ejaculate; hence a cause of obstructive azoospermia. Because the vas deferens is usually affected on both sides, the word "bilateral" is often inserted, as CBAVD. Infertility is inevitable, but can be overcome using in vitro fertilisation with testicular sperm extraction. The cause, however, is usually the presence among the man's genes of one of the serious alleles for the genetic disease cystic fibrosis (which, having recessive inheritance, results when there are two such alleles present); it can also come about when there are one or two of the less serious abnormal alleles for this condition. The more common of the abnormal alleles should therefore be screened for (using a specially set up polymerase chain reaction on white blood cells): should an abnormal allele be present (delta F508 is the most common seriously abnormal one), the woman should be screened too, to predict the chance of cystic fibrosis occurring in the offspring.

The fluid in which cells or tissues, including eggs, sperm and embryos, are grown. It consists of water, salts and nutrients. Different media have turned out best for different purposes. In the early days of in vitro fertilisation, several different media seemed to produce equal results: examples included Ham's F10, Whittingham's T6. Quinn's medium (said to be based on human tubal fluid, though in reality different to the fluid in the fallopian tube) produced better results than the first generation media. Today's third generation media, or stage specific media, give superior results and are used increasingly. Plural: culture media.

A form of collaborative reproduction comparable in some ways to sperm donation (see donor insemination), but different in that eggs for donation are much harder to obtain physically than ejaculated sperm are; generally the egg donor undergoes all the steps needed for in vitro fertilisation up to the stage of egg retrieval.

A biopsy, or removal of one or two cells, from an early IVF embryo for preimplantation genetic diagnosis after in vitro fertilisation.

(ET) Procedure by which the embryo is placed in the uterus or into the fallopian tube after in vitro fertilisation.

Elective single embryo transfer. Choosing to have just one embryo transferred after in vitro fertilisation even though there is more than one embryo that is suitable; the other suitable embryos are frozen and stored. A strategy to increase the chance of taking home a baby by minimising the risk of multiple pregnancy, which carries a higher risk of miscarriage and stillbirths.

Also "fimbriated end": the open, outside end of the fallopian tube in contact with the surface of the ovary, from which it "picks up" the ovulated egg from the ruptured follicle. It's composed of delicate fimbriae -- finger-like projections of the tube lined by cells with tiny hairs (cilia), which beat towards the inside of the tube, carrying the sticky cumulus mass containing the egg into the ampulla before fertilisation. Easily damaged by infection (salpingitis) or careless surgery, after which it may be blocked, resulting in a hydrosalpinx, or have its correct movement inhibited by adhesions.

An operation for sterilisation or "tubal ligation" in which the fimbrial end of each fallopian tube is removed. It has a higher failure rate than most other sterilisation operations on the tubes and it also is more difficult to reverse if the woman intends to regain fertility. It can result in a hydrosalpinx, which can jeopardise success with in vitro fertilisation, and the microsurgery operation to reverse it, salpingostomy, is much less often followed by pregnancy than tubal anastomosis operations are.

An assisted conception procedure in which unfertilised eggs plus sperm (i.e. gametes) are transferred to the fallopian tube, so that fertilisation occurs in the normal place. Because in vitro fertilisation is avoided, for some people GIFT is more morally acceptable than IVF is. The disadvantages are that laparoscopy is required and that for the pregnancy rate to be comparable to IVF too many eggs need to be transferred, risking high multiple pregnancy.

A GnRH-antagonist made by Organon. The first to be FDA approved for women undergoing in vitro fertilisation), with good results when started on day 7 of the cycle, after 5 or 6 days FSH in suppressing the LH surge; the dosage, however, appears to be critical, to avoid over-suppressing natural luteinising hormone. Marketed as Antagon in the US and as Orgalutran elsewhere.

Distinct from the somatic cells that compose most of the body's tissues and organs, germ cells form the eggs and sperm that will form the next generation. Early germ cells are diploid and replicate by mitosis, but during their development they enter meiosis (for eggs this occurs before birth, for sperm it occurs after puberty), so that at the time of fertilisation the contributing sperm and egg are haploid.

A form of collaborative reproduction in which the woman who is the surrogate for the intended pregnancy receives embryos from the commissioning infertile couple, who have undergone in vitro fertilisation, then, by becoming pregnant, carries (or 'gestates') the pregnancy, gives birth, and then gives up the baby to the baby's genetic parents. In principle the practice can be done for altruistic or commercial reasons.

(hPG) A mixture of follicle stimulating hormone (FSH) and luteinising hormone (LH) extracted directly from pituitary glands obtained at autopsies; not used in Australia or elsewhere since 1986, when it was shown that Creutzfeldt-Jakob disease (CJD), a deadly form of dementia, had been transmitted from its use, presumably due to contaminating and infected brain tissue. Before 1986 it had been used mostly for ovulation induction in women with amenorrhea (absent periods) for which other hormones or drugs had not been effective, although sporadic instances of its use for in vitro fertilisation are known in Australia. No new cases of CJD have been reported among former users of hPG since the early 1990s.

A hydatidiform mole in which there is no embryo or fetus. The size of the uterus is often larger than expected from the date of the last menstrual period, often with a high level of serum hCG; there may be bleeding; and there is a classic abnormal appearance on transvaginal ultrasound. Caused by pregnancy following abnormal fertilisation in which the oocyte is 'empty', that is it loses its pronucleus, and either (1) the male pronucleus from a single fertilising sperm doubles (the karyotype of the mole is then always 46,XX, because 46,YY is immediately lethal) or (2) there are two male pronuclei from two fertilising sperm (in which case the karyotype is either 46,XX or 46,XY). Treatment is by vacuum curettage, but there is a persisting danger of cancer (choriocarcinoma) and specialist medical follow-up is essential.

Blockage of the outer, or fimbrial end of the fallopian tube, usually as a result of chronic salpingitis (but also sometimes from peritubal adhesions, from a salpingotomy or partial salpingectomy for a tubal pregnancy, or from fimbriectomy), resulting in its distension by watery contents. An untreated hydrosalpinx (even if only one tube is affected and the other tube is normal) can cause infertility and failure to conceive even with in vitro fertilisation.

The proportion of transferred embryos in an in vitro fertilisation procedure that produce a gestational sac visible on transvaginal ultrasound. Unlike for the conception rate and the pregnancy rate, twins (with separate sacs) are counted separately. An important index of a clinic's success rate with IVF because it reflects embryo quality independently of the number of embryos transferred.

Latin for 'in glass', meaning 'in the laboratory'. (In actual fact, these days, it's usually 'in plastic'!) See also in vitro fertilisation.

Maturation in the laboratory of the egg (as a primary oocyte) obtained from an immature tertiary follicle until it becomes a secondary oocyte competent to be fertilised by sperm using in vitro fertilisation. The smaller the follicle, the lower the proportion of eggs that mature successfully. ICSI can be used to increase the proportion of eggs that will fertilise, but the embryos on average do no better, and so no advantage is conferred by ICSI in this situation.

(LMP) The normal period immediately preceding conception. For convenience, obstetricians calculate the duration of a pregnancy as starting with this date, even though of course it does not truly begin until fertilisation (or, some would say, implantation).

Early experience with superovulation for in vitro fertilisation, particularly at the original US program in Norfolk VA, saw women patients classified into three classes of responders, depending on how many eggs were obtained at egg retrieval. Poorer than usual outcomes could occur with either a low response or a high response (the high responders generally have polycystic ovaries, with a risk of ovarian hyperstimulation syndrome (OHSS). Many maneuvers have been used to try and retrieve more eggs among low responders, such as starting high dose FSH on day 1, the adding of growth hormone, the avoidance of GnRH-agonists etc., all generally without improving the results. Day 3 serum FSH levels can be high in low responders, indicating a depletion of eggs in the ovaries.

A process similar to mitosis in which two successive divisions of a diploid cell's nucleus result in four 'daughter' cells, each with a haploid number of chromosomes. Unlike mitosis, each chromosome therefore duplicates just once (before the beginning of meiosis). Meiosis in humans (and other higher animals) takes place only among the germ cells (oogonia and spermatogonia, which will have been multiplying by mitosis. By differentiating into, respectively, primary oocytes or primary spermatocytes, each with 92 chromatids, meiosis commences. With completion of the first meiotic division the products (including secondary oocytes and spermatocytes) each contain 46 chromosomes. With completion of the second meiotic division the haploid number (23) of chromosomes, suitable for fertilisation, is reached. In the testis, meiosis and the production of new sperm cells (spermatozoa) can continue throughout life, but in the ovary all egg cells that survive commence meiosis about 20 weeks before birth, spending the remaining time (up to 50 years or more) locked up in primordial follicles as primary oocytes. Whereas a primary spermatocyte gives rise to four haploid sperm cells, a primary oocyte produces just one secondary oocyte (the spare 46 chromosomes are dumped into the first polar body just before ovulation), and then one egg cell (the spare 23 chromosomes are dumped into the second polar body after fertilisation).

Oral anti-diabetic drug that improves many aspects of the polycystic ovary syndrome, including lowering of androgens, serum LH, insulin levels and weight, in combination with a low calorie diet; improves development of ovarian follicles and ovulation, as well as responsiveness to clomiphene or gonadotropins if ovulation induction or in vitro fertilisation is necessary.

(MESA) Using microsurgery to dissect the epididymis or rete testis (or sometimes the tubules of the testis itself -- see also testicular sperm extraction) to find motile sperm cells suitable to be aspirated, isolated and prepared for an in vitro fertilisation procedure, usually involving sperm microinjection, especially intracytoplasmic sperm insertion.

Azoospermia caused by low sperm production rates in the testis, including maturation arrest. Can often be overcome with testicular sperm extraction (TESE) followed by in vitro fertilisation utilising intracytoplasmic sperm insertion (ICSI).

A new term for the normal cessation of female fertility up to 10 years before the menopause, being apparent in some women after the age of 33 and most women by 45. Different from the perimenopause, which occurs as egg numbers fall far enough to cause shortening of the menstrual cycle, particularly the follicular phase, and accompanied by elevation of serum FSH when measured during menstruation. If pregnancies are attempted through the oopausal transition, a woman who has had no prior reproductive disturbance will typically experience recurrent miscarriages before developing otherwise unexplained infertility, manifesting in the IVF lab sequentially with unexplained implantation failure of apparently satisfactory embryos, then, in turn, a decreased rate of forming blastocysts, defective cleavage, and then failure of fertilisation. There is no known method of overcoming its effects short of egg donation, except for some hope that the procedure of cytoplasmic transfer might be helpful.

The use of drugs to stimulate the development of follicles in the ovaries to undergo ovulation, such as clomiphene, various preparations containing follicle stimulating hormone (FSH), and human chorionic gonadotropin (hCG). The two main situations for it are: in the treatment of infertility due to anovulation typically when there is oligomenorrhea or amenorrhea; and for superovulation in assisted conception (e.g. in vitro fertilisation and gamete intrafallopian transfer)

The female germ cell, or egg, from the earliest stage (the oogonium in the fetus), through its release from the follicle (ovulation), and (to professional embryologists) through fertilisation up to and sometimes beyond the stage of implantation. Plural: ova.

Can occur when an egg (as a secondary oocyte) undergoes activation (by itself, with some non-specific stimulus, or through fertilisation by a sperm) and starts to divide (it undergoes cleavage), but the male chromosomes are not incorporated and the egg remains haploid; its further development will soon stop, probably well before implantation. Can be the cause of apparent (but false) late fertilisation in the IVF lab.

A tiny, compact packet of excess chromosomes discarded first by the primary oocyte as it becomes a secondary oocyte just before ovulation -- the first polar body, with 46 chromosomes; and second by the secondary oocyte immediately after fertilisation (or after activation by other means) -- the second polar body, with 23 chromosomes. The polar bodies lie in the perivitelline space. The chromosome content of each polar body can be tested as part of a preimplantation diagnosis maneuver to infer whether the corresponding oocyte has an aneuploidy: an extra chromosome in the polar body means a chromosome not enough in the oocyte, and vice versa; this is called polar body analysis.

fertilisation of an egg (a secondary oocyte) by more than one sperm (spermatozoon). In in vitro fertilisation, more common if eggs are recovered that are either immature or overly mature. Evident later, with the appearance of more than two pronuclei. In natural conditions, a cause of a polyploid state in the embryo. Another name for it is polyspermic fertilisation.

(PROST) A form of assisted conception in which in vitro fertilisation (IVF) is used to produce fertilisation of one or more recovered eggs (oocytes). Useful if the potential fertilising ability of sperm (spermatozoa) is in doubt. Transfer is made on the day after egg retrieval and IVF, before the fertilised egg divides (it's at the pronuclear stage); the transfer is made to the fallopian tube to obtain advantages similar to gamete intrafallopian transfer (GIFT) and is made possible by laparoscopy (with anesthesia) or, less successfully, by transvaginal ultrasound (without anesthesia). Synonymous with zygote intrafallopian transfer (ZIFT).

A visible 'blob' (or vacuole) -- there are usually two of them -- inside an egg that has undergone fertilisation or activation by other means, and enclosing the chromosomes from the oocyte (the female pronucleus) and from the sperm (the male pronucleus). Plural: pronuclei. If three pronuclei are observed, the chances are that two sperm have entered the egg (polyspermy).

Ejaculation in which semen, instead of spurting out from the penis during male orgasm, spills upwards into the bladder. Usually has a medically important cause, which requires investigation. Treatment can be successful by isolating spermatozoa from the urine and carrying out some form of assisted conception, such as assisted insemination or in vitro fertilisation.

The form of the oocyte, or egg, produced from the primary oocyte late in the life of the maturing follicle, just before ovulation. The egg stays at this stage until fertilisation by a sperm cell (spermatozoon).

Replication of a diploid organism after combination of haploid male and female gametes, each of which has been produced through the process of meiosis, thus assuring a reassortment of the alleles present among the two parents, in the form of a new, unique, individual genome. Preserved with in vitro fertilisation despite the absence of sexual intercourse. The opposite to cloning.

The result of a reaction of the immune system against sperm cells (spermatozoa) and, by limiting the ability of sperm to show motility, a contributory (or occasionally the only) cause of infertility. Can be present in serum, in cervical mucus or in semen. Can be agglutinating (which make sperm stick in clumps), immobilising (which cripple sperm particularly effectively and kill them), or coating, which interfere with sperm attachment to the zona pellucida of the egg (the secondary oocyte), preventing fertilisation. The screening test for sperm antibodies involves immunobeads.

If fertilisation is the 'marriage' between egg and sperm then syngamy is its 'consummation', as the male and female pronuclei come together for the respective haploid sets of chromosomes to combine into a diploid set. An event of legislative importance in the conservative Australian state of Victoria, after which permission for embryo research becomes much harder to obtain, whatever the views of the couple concerned or an ethics committee might be.

(TESE) Dissection into the testis itself, in men with azoospermia due to maturation arrest, to recover (by 'teasing out') immature sperm cells from the (often small) fraction of testicular tubules there which still contain such cells. The sperm cells are used for in vitro fertilisation using intracytoplasmic sperm insertion (ICSI).

A state of 69 chromosomes, or three times the haploid number, most commonly caused by fertilisation of the egg with two sperm; the embryo that results can develop as far as a fetus, but is doomed to miscarry. The trophoblast of the placenta often undergoes partial changes of a hydatidiform mole. The noun form for this adjective is triploidy (the state of being triploid).

(TEST) A variation of zygote intrafallopian transfer (ZIFT) in which, usually a day after when ZIFT (or PROST) would be carried out, cleaving embryos (at a two-cell to four-cell stage) are transferred to the fallopian tube as part of an in vitro fertilisation program.

Vasectomy reversal, the operation for reversing a sterilisation operation (a vasectomy) in a man involving removal of the blocked part of each vas deferens, in the upper part of the scrotum, and joining by microsurgery one cut end or the vas to the other cut end. Generally not as successful at returning fertility as the equivalent operation in women (tubal anastomosis): the development of sperm antibodies increases with the length of time since sterilisation and limits the effective sperm count after the reversal. Many clinics now carry out cryostorage of some sperm obtained at vasectomy reversal so that if pregnancy does not happen, or azoospermia persists, in vitro fertilisation (IVF) can be carried out with ICSI without requiring a later operation (for MESA) on the man. MESA with ICSI and IVF can be used as an alternative to vasovasostomy.

(ZIFT) A form of assisted conception in which in vitro fertilisation (IVF) is used to produce fertilisation; transfer is made on the day after egg retrieval and IVF, before the fertilised egg divides (it's at the zygote, or pronuclear stage). Useful if the potential fertilising ability of sperm is in doubt. The transfer is made to the fallopian tube to obtain advantages similar to gamete intrafallopian transfer (GIFT) and is made possible by laparoscopy (with anesthesia) or by transvaginal ultrasound (without anesthesia). Synonymous with pronuclear-stage transfer (PROST).