Delays during Reproduction and Their Effects on the Embryo and Fetus

Embryos generated using testicular spermatozoa have higher developmental potential than those obtained using epididymal spermatozoa in men with obstructive azoospermia

“…In addition, unlike under physiological conditions, a blocked epididymal environment can be hostile due to the presence of the remnants of millions of sperm cells. This can further accentuate sperm aging involving, among others, potentially detrimental changes in the nucleus (9,11,12). On the other hand, the obstruction has not been shown to affect the migration of the maturing spermatozoa into the seminiferous tubules from where they are extracted during the biopsy.…”

An Advantage for Young Sperm in the House CricketAcheta domesticus

“…However, one aspect of an ejaculate that is rarely examined is the possibility that the age of sperm in it affects the likelihood of reproductive success. Young sperm cells have several advantages over their older "siblings": they have a higher fertilization ability (Lanman 1968;Tarín et al 2000), the zygotes they produce have higher survival rates (Lanman 1968;Siva-Jothy 2000;Tarín et al 2000), and they have an advantage under sperm competition (Roche et al 1968). All three of these young sperm advantages may favor traits that prevent the transfer, storage, or use of aged sperm by both genders (Siva-Jothy 2000) and are consistent with phenomena such as the regular expulsion of sperm from the male genital tract independent of copulation (Baker and Bellis 1993; Thomsen et al 2003).…”

Prenatal mortality and genetic wastage in man

“…They also demonstrate an increase of heteroploidyincluding both polyploidy and aneuploidy. Several other similar studies have been made in other species (Lanman, 1968b). It may be recalled that embryonic mortality, chromosome anomalies and also menstrual irregularity increase with age, and intrafollicular over-ripening of the oocyte may be important in the effect of age on the risk of heteroploidy.…”

“…It has been shown experimentally in several species that if mating is deliberately -delayed until after ovulation there is an increased embryonic mortality (Beatty, 1957;Lanman, 1968b). This lethal effect of oocyte ageing due to delayed fertilization is partly due to failure of the limitation of sperm penetration, allowing polyspermy to occur with the production of non-viable polyploid zygotes.…”

“…This may occur within the male tract, and may be associated with decreased coital frequency; or it may occur within the female tract if insemination precedes ovulation (Lanman, 1968a;Bishop, 1970). The evidence is controversial, but sperm ageing undoubtedly reduces the chance of successful fertilization.…”