Male biological clock is ticking
Scientists from Bristol and Brunel Universites believe that they have shown evidence for a male “biological clock.”
The study, described in Human Reproduction (2000; 15(8):1703-8), showed that conception takes longer when the man is older, irrespective of his partner's age. Out of 8000 pregnancies studied, 74% were conceived in under six months, 14% in the second six months, and 12% after more than a year. After adjustment for independent variables it was found that women with older partners were significantly less likely to conceive in under six or 12 months. It is not apparent from the study whether the conception took longer because older men's sperm was less fertile or because older men have intercourse less frequently.
The researchers used questionnaires to analyse families who had babies in 1991 and 1992 in the Avon Health Authority. The questionnaires completed by both partners were designed to evaluate the effects of specific