Caffeine delays conception?

Let’s see if I can do this with some, ahem, decorum… do couples trying to get pregnant get to have more fun if the woman drinks lots of coffee, tea or cola?

University of Nevada School of Medicine researchers report in the British Journal of Pharmacology that,

Caffeine reduces muscle activity in the Fallopian tubes that carry eggs from a woman’s ovaries to her womb. “Our experiments were conducted in mice, but this finding goes a long way towards explaining why drinking caffeinated drinks can reduce a woman’s chance of becoming pregnant.”

The researchers go on to explain in their media release that,

Human eggs are microscopically small, but need to travel to a woman’s womb if she is going to have a successful pregnancy. Although the process is essential for a successful pregnancy, scientists know little about how eggs move through the muscular Fallopian tubes. It was generally assumed that tiny hair-like projections, called cilia, in the lining of the tubes, waft eggs along assisted by muscle contractions in the tube walls.

By studying tubes from mice, Professor Ward and his team discovered that caffeine stops the actions of specialised pacemaker cells in the wall of the tubes. These cells coordinate tube contractions so that when they are inhibited, eggs can’t move down the tubes. In fact these muscle contractions play a bigger role than the beating cilia in moving the egg towards the womb. “This provides an intriguing explanation as to why women with high caffeine consumption often take longer to conceive than women who do not consume caffeine,” says Professor Ward.

Discovering the link between caffeine consumption and reduced fertility has benefits. “As well as potentially helping women who are finding it difficult to get pregnant, a better understanding of the way Fallopian tubes work will help doctors treat pelvic inflammation and sexually-transmitted disease more successfully,” says Professor Ward. It could also increase our understanding of what causes ectopic pregnancy, an extremely painful and potentially life-threatening situation in which embryos get stuck and start developing inside a woman’s Fallopian tube.

So does this research explain why caffeinated women take longer to conceive? Is there any evidence that, in fact, hyper-caffeinated women take longer to conceive in the first place?

First and contrary to the researchers claim, this experiment was not “conducted in mice.”

In fact, the mice were killed and their oviducts were then removed, segmented, frozen in liquid nitrogen, pinned to a recording chamber, and exposed to a caffeine solution to measure changes in transmembrane electrical potential.

Re-read the media release (above) and see if you think the researchers fairly describe what they did.

Past the fact that this experiment doesn’t necessarily explain any phenomena that occurs in living mice, might it have any relevance to humans?

The researchers claim it is, citing two 1990s-era epidemiological studies reporting that caffeine-consuming women take longer to conceive:

• In the 1993 American Journal of Epidemiology study “Association of Delayed Conception with Caffeine Consumption“, women who consumed more than three cups of coffee per day reportedly were more than twice as likely to experience a delay in conception of one year or more. But as the data are suspect — e.g., caffeine intake was assessed once by self-report, data about how hard and/or correctly the women tried to get pregnant were not collected, and the only confounding risk factors considered were method of birth control used, parity, and number of cigarettes per day — this study doesn’t truly associate caffeine consumption or delay in conception with anything except wishful thinking.
• In the 1997 American Journal of Epidemiology study ““Caffeine intake and delayed conception: a European multicenter study on infertility and subfecundity. European Study Group on Infertility Subfecundity”, the associations are weak and or nonsignificant even for women drinking more than the equivalent of 5 cups of coffee per day.
• In the 1998 Reproductive Toxicology study “Caffeine intake and fecundability: a follow-up study among 430 Danish couples planning their first pregnancy“, nothing of statistical significance was reported among the couples.

So to answer the question posed at the outset, there is no credible or compelling evidence that women’s caffeine consumption will extend pre-conception sex life.