Declining Trends in Conception Rates in Recent Birth Cohorts of Native Danish Women: A Possible Role of Deteriorating Male Reproductive Health

Wolfgang Lutz, T.K. Jensen, T. Sobotka, M.A. Hansen, A.T. Pedersen, N.E. Skakkebæk

Publication: Scientific journalJournal articlepeer-review


Recent findings of poor semen quality among at least 20% of normal young
men in Denmark prompted us to use unique Danish registers on births and
induced abortions to evaluate a possible effect of the poor male fecundity on
pregnancy rates among their presumed partners – the younger cohorts of
women. We have analysed data from the Danish birth and abortion registries as
well as the Danish registry for assisted reproduction (ART) and defined a total
natural conception rate (TNCR), which is equal to fertility rate plus induced
abortion rate minus ART conception rate. A unique personal identification
number allowed the linkage of these databases. Our database included 706 270
native Danish women born between 1960 and 1980. We used projections to estimate
the fertility of the later cohorts of women who had not yet finished their
reproduction. We found that younger cohorts had progressively lower TNCR
and that in terms of their total fertility rate, the declining TNCR is compensated
by an increasing use of ART. Our hypothesis of an ongoing birth cohort-related
decline in fecundity was also supported by our finding of increasing and substantial
use of ART in the management of infertility of relatively young couples
in the later cohorts. Furthermore, the lower rates of induced abortion among
the younger birth cohorts, often viewed as a success of health education
programs, may not be fully explained by improved use of contraception. It
seems more likely that decreased fecundity because of widespread poor semen
quality among younger cohorts of otherwise normal men may explain some of
the observed decline in conception rates. This may imply increasing reproductive
health problems and lower fertility in the future, which is difficult to reverse
in the short term. The current and projected widespread use of ART in
Denmark may be a sign of such an emerging public health problem.
Original languageEnglish
Pages (from-to)81 - 89
JournalInternational Journal of Andrology
Issue number2
Publication statusPublished - 1 Nov 2008

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