Is human fecundity declining?

Abstract

Summary The decreasing trends in fertility rates in many industrialized countries are now so dramatic that they deserve much more scientific attention. Although social and behavioural factors undoubtedly play a major role for these trends, it seems premature, and not based on solid information, to conclude that these trends can be ascribed to social and behavioural changes alone. There is evidence to suspect that changing lifestyle and increasing environmental exposures, e.g. to endocrine disrupters, are behind the trends in occurrence of male reproductive health problems, including testis cancer, undescended testis and poor semen quality. These biological factors may also contribute to the extremely low fertility rates. However, the necessary research is complex and requires non-traditional collaboration between demographers, epidemiologists, clinicians, biologists, wild life researchers, geneticists and molecular biologists. This research effort can hardly be carried out without major support from governments and granting agencies making it possible to fund collaborative projects within novel research networks of scientists.

A data‐driven search for semen‐related phenotypes in conception delay

“…With increasing concern about the impact of endocrine disrupting chemicals on male fecundity, particularly in light of a large fraction of male infertility attributed to such exposure (Hauser et al ., 2015), coupled with evolving biomarkers of male fecundity (Isobe, 2012; Kovac et al ., 2013), environment‐wide association study (EWAS) approaches offer options for identifying predictors of male fecundity and fertility. Novel approaches are needed if we are to understand the relatively high prevalence of male infertility in some populations (Louis et al ., 2013), reported declines in sperm morphology (Rolland et al ., 2013) and more generalized concerns about declining human fecundity (Skakkebaek et al ., 2006; te Velde et al ., 2010). …”

Expressing urine from a gel disposable diaper for biomonitoring using phthalates as an example

“…diethylhexyl phthalate, dibutyl phthalate, and butyl benzyl phthalate) results in many changes in the male reproductive tract, such as decreased anogenital distance, hypospadias, cryptorchidism, disturbed development of prostate, epididymis, vas deferens, and seminal vesicles, retained nipples, and decreased sperm production (Mylchreest et al, 1998(Mylchreest et al, , 1999(Mylchreest et al, , 2000(Mylchreest et al, , 2002Gray et al, 2000;Kavlock et al, 2002a,b,c,d,e;Lottrup et al, 2006;Skakkebaek et al, 2006;Weisbach et al, 2006). The critical window for all of these effects is the latter half of gestation (days 12-21), which is the time during which male sexual differentiation occurs (Mylchreest et al, 1999).…”

“…45X/46XY and androgen insensitivity) also have high risk of testicular cancer, often combined with cryptorchidism and hypospadias (Savage & Lowe, 1990). It has been proposed that all these human disorders (testicular germ cell cancer, cryptorchidism, hypospadias, and low sperm counts) have common origins in fetal life, and thus they all represent different symptoms of the same underlying entity called testicular dysgenesis syndrome (Aarskog, 1970;Scully, 1981;Sharpe & Skakkebaek, 1993;Skakkebaek et al, 2001Skakkebaek et al, , 2006Sharpe, 2003;Asklund et al, 2004). Since the testicular and other changes in dibutyl phthalate-exposed rats have also been reported in human testicular dysgenesis syndrome, it has been proposed that in utero exposure of the rat to dibutyl phthalate is a possible model for studying human testicular dysgenesis syndrome (Fisher et al, 2003).…”

Calcium- and integrin-binding protein-1 is down-regulated in the sperm of patients with oligoasthenozoospermia

“…Infertility is a worldwide reproductive health problem that affects about 15 % of couples [1], and the marked decrease in fertility rates in many industrialized countries demand further scientific attention [2]. Half of infertility cases are due to male factors, and 75 % of such cases are idiopathic [3].…”