The ageing gamete in relation to birth control failures and Down syndrome

Abstract

Some indirect relationships between contraception failures and offspring with a pathological condition are reviewed, and a causal connection between them is suggested. This hypothesis is supported by the decreasing incidence of Down syndrome (DS) in general in recent years, and the increase among the younger maternal age categories as well as the effect of birth order. A more than doubled incidence of DS children among young Catholic mothers and the fact that conceptions of children with DS are preceded by unusually long periods of abstinence are emphasised and discussed. These data offer circumstantial evidence that the conceptions that occur despite application of the so called "natural" family planning methods in particular are at high risk. The impact of reproductive biological failures ("nature") and of reproductive behaviour ("nurture") on the human gametes can be disentangled by thorough studies of the epidemiology of major and minor congenital anomalies.

Twinning, nonrighthandedness, and fusion malformations: Evidence for heritable causal elements held in common

“…The conditions imposed in those animal studies favor twinning, males, chromosome anomalies, malformations, and prenatal death. The most comparable conditions so far identified in humans produce the same range of effects [Guerrero, 1974;Guerrero and Rojas, 1975;Harlap et al, 1985;Jongbloet, 1983Jongbloet, , 1984Jongbloet, , 1985Jongbloet et al, 1982;Jongbloet and Vrieze, 19851. It may help at this point to remember that the human lacks the stringent physiological limits on female sexual receptivity that protect other mammals from fertilization of overripe gametes.…”

A temporary increase of down syndrome among births of young mothers in Norway: An effect of risk unrelated to maternal age?

“…More young people may have used the "rhythm technique" to prevent conception in the period in question. This possibility is related to the so-called preovulatory overripeness ovopathy hypothesis [Jongbloet, 1985;Jongbloet and Vrieze, 19851, which is based on the observation that disomic ova have an atypical ovulation pattern. However, this explanation does not seem likely, since more effective contraceptive methods are available.…”

“…Estimated proportion of Down syndrome c a m among liveborn in Norway according to model 2 (two-wgrnent model), during 1973-1984, 1985-1986 Table 111, final model uterine selection may have been disturbed. Some investigators have hypothesized that the high proportions of Down syndrome among older mothers may be caused by a deficiency in a natural tendency to abort affected fetuses [Erickson, 1978;Sved and Sandler, 19811. Lamson and Hook [ 19801 fitted two independent segments of linear curves to the logarithm of the maternal age-specific proportions of Down syndrome.…”

“…Despite the fact that some of these cases are probably reported to the registry, they do account for the drop in the risk of Down syndrome in the 40-44 years group in recent years. Thus, the truncation of the data at 38 years of maternal age for 1985-1986and 1987seems warranted. Baird and Sadovnick [1988 recently reviewed 18 reports on secular trends in maternal age specific Down syndrome rates.…”

Aging gametes in relation to incidence, gender, and twinning in Down syndrome

“…The significantly increased incidence of DS in the religious population independent of maternal age confirms the findings of previous studies on this population [Harlap, 1974;Sharav, 19851. The finding of a higher rate of DS in the religious populations both Catholic and orthodox Jewish has been hypothesized to be compatible with delayed fertilization [Jongbloet, 1985;Sharav, 19851. Thus the finding in the Jerusalem DS population of 2 additional factors, a higher incidence of males and twinning, which have also been shown to be associated with delayed fertilization, provides additional circumstantial evidence in support of this hypothesis.…”