Infertility that is not 'absolute', or 'complete infertility' -- that is, there is a chance of pregnancy: it is not sterility (these last 3 terms are synonyms) -- but the chance of getting pregnant each month (fecundability or monthly fertility) is reduced. More or less definite causes can include oligospermia, polycystic ovary syndrome and other causes of oligomenorrhea, endometriosis, peritubal adhesions, fibroids (especially submucous fibroids) and increased age, especially of the woman. Synonymous with relative infertility.

One of the two most important variables (the other is time left for conception) that determines the chance of still getting pregnant naturally in subfertility, including unexplained infertility. The longer the duration of infertility, the smaller the chance each month as time goes on. See also fecundability and time to pregnancy.

Technical speak for the monthly chance of pregnancy, or monthly fertility rate, either for an individual (measured over time) or for a population (the number of conceptions occurring in one month). For any individual with unexplained infertility and in milder cases of subfertility, chiefly determined by the duration of infertility (or, in cases of secondary infertility, in which past fecundability is being estimated, determined by time to pregnancy). Once calculated this way, an estimate of the chance of still getting pregnant naturally (as opposed to undergoing assisted conception) will chiefly be determined by the time left for conception.

A reproductive strategy where survival of a species is optimised by placing a premium on individual survival despite fluctuations of the environment. Favors large animals (and large animals favor this strategy) -- animals that get pregnant more than once and the offspring of which require postnatal care before sexual maturity is reached. Spacing of pregnancy is important for survival of mother and offspring, and thus favors the evolution of a genetic basis for subfertility. The opposite reproductive strategy to r-selection. The word comes from the environment's Karrying capacity.

Synonymous with subfertility.

(SCSA) A measurement of the proportion of sperm cells that have damaged DNA. Fewer than 15% is consistent with normal fertility; 15%-30% can result in subfertility; and more than 30% may cause sterility or recurrent miscarriage.

One of the two most important variables that determine the chance of still getting pregnant naturally in subfertility and unexplained infertility (the other is duration of infertility). The longer the time still available the better the chance that, sooner or later, pregnancy will happen. Broadly limited by the female partner's age, but personal circumstances and ambitions within the biologically available timeframe might shorten it, leading to a decision to seek treatment with assisted conception.

An estimate of likely fertility in secondary infertility, where the time it took to get pregnant the first time is used as a very approximate guide to what might be expected next time round. Of limited usefulness, but if it took a long time to get pregnant the first time it will typically take at least as long next time. Achieving a pregnancy does not usually itself permanently cure subfertility.