Contraceptive failure in the United States: a critical review of the literature

The overall goal of this paper is to provide for the first time a comprehensive critical review of the literature on contraceptive failure in developed countries, primarily the United States. The first two sections of our paper lay the groundwork for a critical assessment of the extensive body of studies on this subject, by systematically exploring the concepts and measurement of contraceptive efficacy and the methodological pitfalls that snare many investigators and compromise their results. The next two sections focus on results in the literature. First we provide a method-by-method critique of the available studies and then we summarize our conclusions in a single table that provides efficacy information necessary for women and couples to make an informed choice of a method of contraception. We close with a set of substantive observations and also a set of methodological recommendations intended to improve the quality and comparability of findings from future research.     

Zinc feeding and fertility of male rats

Supplementation of the diet of adult male rats with 4,000 ppm zinc as ZnSO4 for 30 to 32 days increased the zinc content in the testis and sperm by 25 and 18 per cent respectively, but did not change the same in accessory reproductive tissues, e.g. epididymis, seminal vesicle and prostate. The incidence of conception from mating between normal females and zinc fed males was lower as compared to mating between normal females and control males. This observation indicated reduced fertility of the males resulting from additional zinc ingestion. Motility of the sperm collected from the epididymis (tail) of the zinc treated rats was found to be inhibited. It has been suggested that excess zinc in the sperm was responsible for their poor motility and hence a reduced fertilising capacity.