Chance -- expressed as a ratio, proportion or percentage. If the word is unqualified, it usually means absolute risk (the actual risk in a group of the population), in contrast to relative risk (which measures one person's risk compared with another person's).

Your actual chance of having something or being affected by something (so it does not usually mean "absolutely" in the sense of "one hundred percent", as in absolute infertility). Usually given as a ratio, proportion or percentage: for example, the (absolute) risk of having at least some visible endometriosis for a woman in her 40s is about 20 in 100, or 20 percent; the chance or the risk of pregnancy each month for a normal young couple (normal fecundability) is also about 20 percent, usually expressed as 0.2 (i.e. as a proportion); the risk of a woman developing cancer of the ovaries by the time she reaches her seventies, in North America, Europe or Australia, is about 1-in-90 (or about 1.1%).

The chance of having something or being affected by something compared with people in a comparable situation. Usually given as a ratio, a proportion or a percentage as in the chance of having endometriosis; if your sister has it, you have a relative risk of 7:1 -- or seven times the risk -- compared with the general population of women of the same age; your relative risk of developing cancer of the ovaries if you've accumulated 10 years on the oral contraceptive pill is 1:5, 0.2 or 20.

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.

Bleeding (usually irregular and light, i.e. 'spotting') while on the birth control pill (the oral contraceptive pill) or while taking a progestogen. With regard to the pill, it is common (and of no sinister importance) in the first few months of pill use; but if it happens after many months' satisfactory use of the pill then it can signal: (1) interference with the efficacy of the pill (i.e. a risk of ovulation and pregnancy) by an illness with diarrhea, simultaneously taking antibiotics, or a drug interaction (taking additional medications that speed up the pill's metabolism; or (2) coexisting pathology of the cervix or the uterus. Unexplained or persistent breakthrough bleeding means you should see your physician.

An ectopic pregnancy located in the wall of the cervix. A particularly dangerous condition because of the risk of uncontrollable bleeding.

Traditionally, any miscarriage revealed to be complete upon careful inspection of the expelled pregnancy tissue (the "products of conception", meaning that a uterine curettage was not necessary to avoid the risk of retained tissue causing more bleeding or infection. Nowadays we can distinguish a complete from an incomplete miscarriage (and whether or not a curettage should be done) with a transvaginal ultrasound, which can reveal significant retained tissue.

A serious genetic disease (with a recessive inheritance pattern) characterised by a major disturbance of the body's mucus secretions, and thus a cause of incapacitating disease of the lungs. Important in our context because the heterozygous (or carrier) state in men can manifest with azoospermia due to congenital absence of the vasa deferentia -- the infertility of which is nowadays able to be overcome with testicular sperm extraction and ICSI, thus risking inadvertent transmission.

Due to trisomy 21. Chromosome 21 is the smallest of the "autosomes" (the non-sex chromosomes): trisomies of the other autosomes tend to be lethal at an earlier stage of embryonic or fetal development, and so are seen much more rarely. Diagnosis of Down's syndrome requires a karyotype, obtainable from pregnancy tissue by chorionic villus sampling (CVS) or amniocentesis. Screening for increased risk in pregnancy can be performed by triple screen or by looking for nuchal translucency at transvaginal ultrasound.

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.

(ERT) The therapeutic use of estrogen to stop the effects of menopause after the ovaries have been removed or have stopped functioning. If the uterus is still present the hormone regimen must include at least 11 days' progestogen usage each month, or there will be a risk of endometrial hyperplasia and hence endometrial cancer.

A trisomy with a karyotype of 47,XYY -- i.e. a male with an extra Y-chromosome. Affected men tend to be tall. Surveys of penal institutions have indicated a higher than expected frequency, implying that affected men are at increased risk of being criminals. This assertion is controversial.

A controversial and emotionally hazardous way of dealing with a higher-order multiple pregnancy (such as quadruplets, quintuplets, or higher) in which, all the embryos or fetuses are at risk of being lost before viability. The technique involves carrying out transvaginal ultrasound and injecting a lethal substance (such as air or a solution of potassium) into the visibly beating heart of one or more of the embryos, so reducing the number of surviving embryos to three, two or one. Generally regarded as a more stressful procedure than even an induced abortion, both for the person undergoing the operation and for the ultrasound doctor asked to do it. Few people regard the availability of fetal reduction to mean that the greatest care does not need to be taken to avoid higher-order multiple pregnancies in assisted conception programs. There's a hazard: loss of the remaining fetuses from miscarriage; but the risk of this, with an experienced ultrasound doctor or fetal medicine specialist, is low.

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.

Generic name for Dimetriose, a drug used in the treatment of endometriosis that inhibits ovulation and blocks the action of both estrogen and progesterone; risks and side effects are similar to danazol; it is usually taken just twice weekly, by mouth.

An event, usually unwanted, sometimes in the sense of a penalty. Unlike risk, which has a number attached to it (it's quantitative), a hazard is 'yes' or 'no': it's either realised, or experienced, or it's not; although one hazard can be worse to experience than another, you can't put a figure on it (it's said to be qualitative).

A naturally occurring 'anticoagulant', or substance that stops blood from clotting. Used in medicine generally to prevent or to treat thrombosis, and sometimes in pregnancy to reduce the risk of miscarriage in someone who has had recurrent miscarriages by improving blood flow in the placenta. Administered by injection under the skin.

A "minimally invasive" surgical operation at which instruments are passed through the wall of the abdomen: (1) for the diagnosis of abnormalities of the abdominal or pelvic organs (such as the fallopian tubes, ovaries and uterus) and to diagnose endometriosis; or (2) therapeutically, to reach the fallopian tubes for certain assisted conception procedures (see gamete intrafallopian transfer and zygote intrafallopian transfer). Carries the risks of surgery (damage to internal organs, hemorrhage, infection) and the risks of general anesthesia.

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.

(LPD) A luteal phase that is shorter than optimal for a fertilised egg to undergo implantation. Very likely if the luteal phase is shorter than normal (11 to 16 days), but not all luteal phases within this range are innocent. Often caused by a prior defect of the follicular phase or of the development of the ovulating tertiary follicle (the preovulatory follicle) and hence there can be a defect of the egg itself (if ovulation has actually occurred) or there can be a luteinised unruptured follicle -- any of which will either increase the risk of miscarriage or will prevent pregnancy altogether for that cycle. Synonymous with luteal phase insufficiency.

A miscarriage that should have happened but hasn't. As a result, the pregnancy tissue in the uterus gets tougher and more difficult to get out with a uterine curettage -- which is the only treatment for it, but risks producing intrauterine adhesions. The pregnancy test can stay positive for many weeks or even months.

Identical or monozygotic twins in which the split has occurred after formation of the blastocyst, so that the twins share the same gestational sac (or amniotic cavity). There is a much higher risk of complications than in the more usual situation where twins do not share the same sac, because the fetuses or the umbilical cords can get tangled up.

Mitochondrial DNA. The small amount of DNA found in the mitochondria. mtDNA is the genetic code for 13 proteins involved in metabolism. Because mtDNA is much less stable than the DNA in the chromosomes (where the huge bulk of genetic code is stored), mutations accumulate with time at a greater rate than that for chromosomal DNA -- and eventually limit how well a particular cell or tissue can function with increasing age. Because all of the mtDNA you have you inherited from your mother (you derive your mitochondria from the egg you came from), we could have an explanation: (1) why all eggs are formed before birth (so the mitochondria don't have to keep on dividing too often and risking genetic errors); and (2) why miscarriages and infertility get commoner with age (as the egg's several thousand mitochondria begin to succumb to genetic errors).

A measurement done at transvaginal ultrasound of tissue in the neck of the fetus; if excessive, it implies a substantially increased risk that the fetus is affected by Down syndrome and Turner syndrome.

A syndrome occurring in late pregnancy marked by an increase in blood pressure, swelling of the ankles by fluid, and the appearance of albumin in the urine, associated with reduced blood flow to the placenta, therefore putting the fetus at risk of death, or stillbirth, and putting the mother at risk of complications from high blood pressure, convulsions (eclampsia), kidney failure, liver failure and death. Treated with drugs to lower the blood pressure and to prevent convulsions, while expediting the delivery of the baby.

The use of somatic cell nuclear transfer or embryo splitting to secure pregnancy and a new individual intended to be virtually genetically identical to the person who donated the cell nucleus used or genetically identical to siblings resulting from embryo splitting (which in effect is the intentional creation of identical twins, or triplets etc.). Practiced in animals, especially farm animals. Considered ethically abhorrent because of strong ethical arguments within the fields of deontological ethics (including a duty not to intentionally violate the biological principle of sexual reproduction involving genetic reassortment and individual difference), teleological ethics (including the very high risk of severe birth defects with SCNT) and utilitarian ethics (where arguments are based on considerations by and for society generally).

Measurement of alpha fetoprotein in blood serum. High levels can indicate a birth defect involving the brain or spinal cord, such as anencephaly or spina bifida (confirmed if amniocentesis shows high AFP levels in the amniotic fluid). Low levels can indicate an increased risk of Down syndrome (or trisomy 21), trisomy 18 and, occasionally, Klinefelter syndrome, signaling the need for a karyotype of the fetus's tissues by chorionic villus sampling (CVS) or amniocentesis.

A general term used by obstetricians or pediatricians to refer to a fetus or newborn baby that seems smaller than it should be for the assumed duration of the pregnancy so far. The three main causes are a genetic abnormality of the fetus; insufficient nutrition for an otherwise normal fetus; and an incorrect calculation of the dates, maybe because ovulation and conception took place later than the usual two weeks after the last menstrual period. Recent research shows that women with infertility might be at higher risk of small-for-dates babies when they do get pregnant.

A point at which statistics indicate that a set of measurements or observations does not just actually differ from normal (i.e. it's abnormal) or from a control group, but that the observed difference is unlikely (typically less than a 1-in-20 risk) to have come about just by the effects of chance (we then say that there is a P-value -- for Probability -- of less than 0.05 ... which is what 1-in-20 is when expressed as a proportion). Footnote: One logical follow-on from this is that if you study 20 different variables for such statistical significance the odds are that one will have a P-value less than 0.05, just by the expectations of chance! In practice, when multiple observations like this are being made statisticians will put a tougher criterion on what is 'statistically significant', such as P less than 0.02 or 0.01. For academic legitimacy, P values should be set before looking at the data, not afterward.

Intentional induction of multiple ovulations at once, using injections of follicle stimulating hormone and human chorionic gonadotropin, for assisted conception. Inevitably there is a risk of multiple pregnancy unless egg retrieval is performed.

A state of intersex in which the karyotype is male (i.e. 46,XY), the gonads are testes (hence also male), but the body is completely unresponsive to testosterone and to its metabolite dihydrotestosterone, so it develops in the female way, with a normal vulva and vagina apparent at birth, and with normal development of the breasts at puberty. Because the testes still secrete anti-Mullerian hormone, there's no uterus. Invariably these children are raised as girls, normal except for their primary amenorrhea and their infertility. Specialist medical supervision is needed, because there is an increased risk of cancer in the abnormal gonads. Synonymous with androgen insensitivity syndrome (complete form).

An increase in the tendency of the blood to clot, as in 'thrombosis'. In primitive, evolutionary times, a survival advantage for women giving birth, when loss of blood would on average be less, but exacting a price in terms of increased risk of stroke or venous thrombosis. The thrombophilias are implicated in disturbances of pregnancy, including recurrent miscarriage and stillbirth.

Twisting of an organ on its vascular pedicle, risking necrosis. Can happen to the testis in boys, especially after an injury to the scrotum, or to the ovary and fallopian tube, either spontaneously during adolescence or when enlargement from superovulation has produced ovarian hyperstimulation syndrome (OHSS). An operation to untwist it can save the affected organ, if carried out quickly enough.

A screen for congenital abnormalities of the fetus done on the mother's blood serum during pregnancy to look for fetal trisomy, including Down syndrome. The original test comprised measurements of (1) serum alpha fetoprotein (decreased in the trisomies), (2) serum hCG (increased in trisomy 21, decreased in trisomy 18), and (3) serum estriol (decreased in trisomy 21, increased in trisomy 18). Note that only 60% of pregnancies with Down syndrome will be revealed by a triple test. Refinements have taken place, with 'free beta' (part of the hCG molecule) replacing hCG itself, and with the addition of PAPP-A replacing estriol, increasing the sensitivity and specificity of the test. Further gains in sensitivity and specificity comes from adding an ultrasound test for nuchal translucency. Even so, false positive tests are possible, which will be resolved only by performing CVS or amniocentesis, and so also are false negative tests, which means that CVS and amniocentesis should still be considered in otherwise high-risk situations.