Joffe M
Department of Epidemiology and Public Health, Imperial College School of Medicine, London, UK.
Lancet. 2000 Jun 3;355(9219):1961-5. doi: 10.1016/S0140-6736(00)02328-X.
There is evidence of a decline in semen quality in some countries, including Britain, in recent decades. This retrospective cohort study examined the hypothesis that biological fertility had also declined. The trend in couple fertility was assessed by means of time to pregnancy (TTP--a sensitive and validated measure of fertility.
A representative sample of the British population aged 16-59 years was surveyed. TTP was obtained for all births conceived after unprotected intercourse that began during 1961-93, excluding contraceptive failures. The sample size was 1540.
In contrast to the original hypothesis, this study found that fertility has increased; the rising trend was accompanied by slight dips during 1976-80 and 1986-90. These results were consistent between male and female respondents, and undiminished by adjustment for possible confounding factors. A stronger and more consistent relation was found with the year when unprotected intercourse started (a period effect) than with the year of birth of either partner (a birth cohort effect).
The findings could not be explained by trends in age at first birth, increased treatment of subfertility, or changes in oral contraceptive use. If a decline in male fertility has occurred, it has been more than compensated for by a countervailing increase in couple fertility.
有证据表明，近几十年来，包括英国在内的一些国家精液质量有所下降。这项回顾性队列研究检验了生物生育能力也已下降这一假设。通过受孕时间（TTP，一种敏感且经过验证的生育能力衡量指标）评估夫妇生育能力的趋势。
对年龄在16 - 59岁的英国人群进行了一项代表性抽样调查。获取了1961 - 1993年期间开始的未采取避孕措施性交后所有出生案例的受孕时间，不包括避孕失败情况。样本量为1540。
与最初的假设相反，本研究发现生育能力有所提高；上升趋势在1976 - 1980年和1986 - 1990年期间伴有轻微下降。男性和女性受访者的结果一致，且在对可能的混杂因素进行调整后并未减弱。与未采取避孕措施性交开始的年份（时期效应）相比，与任何一方的出生年份（出生队列效应）之间的关系更强且更一致。
这些发现无法用初产年龄趋势、不育治疗增加或口服避孕药使用变化来解释。如果男性生育能力确实出现了下降，那么夫妇生育能力的相应增加已对其进行了更多的补偿。
