Tests on mice have shown why drinking coffee reduces the chances of women getting pregnant.
A study published in the British Journal of Pharmacology this week explained that caffeine reduces muscle activity in the Fallopian tubes which 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,” said Sean Ward, a professor from the University of Nevada-Reno School of Medicine, who also authored the study.
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, Mr. 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.
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,” Mr. Ward said.
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,” Mr. Ward said.
It could also increase 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.