Feasibility of surveillance of changes in human fertility and semen quality*

Abstract

There is concern that male fertility is declining, but this is difficult to study because few men volunteer for studies of semen quality, and recruitment bias may over-represent the subfertile. The Human Reproduction Programme of the World Health Organization developed a protocol for multicentre studies of fertility involving a questionnaire for pregnant women to obtain time to pregnancy (TTP): the number of menstrual cycles taken to conceive. Male characteristics and semen quality will be determined in a subset of the partners. Our aim was to validate the TTP questionnaire, and to examine potential recruitment bias and feasibility of conducting large-scale surveillance of fertility. The questionnaire was administered to 120 pregnant women (16-32 weeks). Validation included internal reliability by consistency of responses, test-re-test reliability by repeat administration (20 women) and accuracy by comparison of gestational age from first antenatal ultrasound and menstrual dates. Internal reliability was high. Agreement between categorical responses on re-testing was very good (k > 0.8). In both the re-test and gestational age analysis, differences in TTP of 1 cycle were found (standard deviation <0.25 cycles). In this small pilot study there was no evidence of recruitment bias. Response rates indicate the feasibility of surveillance of fertility in large maternity centres.

Are volunteers delivering semen samples in fertility studies a biased population?

“…Of course, studies only based on TTP where high participation rates (typically 60-80%) are usually observed do not suffer this disadvantage (Joffe 1997;Stewart et al, 2001;Slama et al, 2004) while not devoid of other sources of bias (Weinberg et al, 1994). However, TTP and semen quality do not provide the same information on the male side of reproductive function (Slama et al, 2004).…”

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“…Such studies evaluating sperm counts over time fail to address whether any deterioration in semen quality, albeit controversial, is accompanied by a reduction in human fertility. This can be measured by assessing changes in the time taken to achieve a pregnancy (29).…”