Over a year ago, I summarized what I think is one of the best studies looking at the relationship between caffeine and fertility: http://draimee.org/tag/caffeine/. There is new research that may lead me to change how I talk to my patients about caffeine.
According to a study published recently in the British Journal of Pharmacology, caffeine appears to reduce the muscle activity in the fallopian tubes that carry eggs from the ovary to the uterus. Before you start feeling guilty for your morning cup of coffee, you should realize that the study was conducted in mice, so it’s not certain how these results apply to people.
Many of my patients don’t realize that a sperm cell meets the egg in the fallopian tube. The fallopian tubes are attached to the sides of the uterus. Fertilization actually occurs in the tube and over the course of a few days, the embryo travels down the tube until it lands in the uterus where it will hopefully then implant (stick to the wall of the uterus). So if a fallopian tube can’t do what it needs to do (help transport the embryo into the uterus and nourish the embryo) it will be hard to achieve pregnancy. If we find the same findings in humans as the investigators did with mice we may have to change how we counsel women when they’re trying to conceive.
Concerns about the health effects of coffee and other caffeinated beverages for pregnant women — or those trying to conceive — have been an issue for years. Some studies suggest too much caffeine can increase the risk of miscarriages, while others haven’t found any link. And other research has associated caffeine intake with reduced fertility in women.
These studies are all about statistical links and associations made by surveying women about their coffee drinking habits. There’s no way to definitively conclude that consuming more caffeine directly affects fertility and pregnancy since it’s unethical to randomly assign a group of women to drink coffee just to see whether they will be harmed by it.
A 2003 study that found women whose caffeine intake was under 50 milligrams a day — the amount in less than one cup of brewed coffee — had higher pregnancy rates after undergoing in vitro fertilization compared with those with higher caffeine intakes who also had IVF.
We advise to keep intake to ideally 1 cup per day and no more than 2. But if you can go with decaf, that would be ideal. There are ongoing studies about the relationship between caffeine and infertility so stay tuned.