A small study of 73 women from North Middlesex Hospital in London found that artificial insemination was over three times as successful when using the second of two sperm samples collected within the same one-hour period. This strategy led to a 20.5 percent pregnancy rate, compared to the usual 6 percent rate for the intrauterine insemination method studied, according to results presented at the annual European Society of Human Reproduction and Embryology meeting. So what could this mean for your sex life?
Since this scenario mimics having sex more than once within an hour, the study's lead author, Gulam Bahadur, D.Phil., a fertility specialist, told The Daily Mail that "it would be reasonable to assume the same effect would apply to men trying to conceive naturally." In other words, you now have an excuse (not that you needed one to begin with) to ditch your evening plans and spend the night in bed if you're looking to increase your chances of getting pregnant.
This all comes with the caveat that ejaculating twice within an hour is not possible for every guy, so obviously this technique has its limitations. However, human reproduction scientist Jackson Kirkman-Brown, M.B.E., P.hD., told The Daily Mail that the spike in pregnancies with the second sample was likely due to the higher quality of younger sperm, which would imply that waiting less time between sessions is more effective even if you can't get it down to one hour.
These results would also imply that if you're not looking to conceive, sex marathons may present more of a pregnancy risk than one-time sessions — which isn't surprising. There's something to be said for going at it all night (or, to be more realistic, a couple times in one night), but, as always, protection is key if you're not looking to get pregnant.