A new study of 4,000 women found that those who reported drinking five or more cups of coffee a day at the start of IVF treatment reduced their chance of success by 50 percent. The Danish researchers described heavy coffee drinking as being "comparable to the detrimental effect of smoking."
The study was presented Tuesday, July 3, at the annual meeting of the European Society of Human Reproduction and Embryology in Istanbul by Ulrik Schiøler Kesmodel from the Fertility Clinic of Aarhus University Hospital in Denmark.
Results showed that the consumption of five or more cups of coffee a day reduced the clinical pregnancy rate by 50 percent. Information on coffee consumption was gathered at the beginning of treatment (and at the start of each subsequent cycle). No effect was observed when the subjects reported coffee consumption of less than five cups.
"Although we were not surprised that coffee consumption appears to affect pregnancy rates in IVF, we were surprised at the magnitude of the effect," said Kesmodel in a release.
Most experts agree that moderate amounts of caffeine -- less than 300 milligrams (mg) a day, or the amount in 16 ounces (473 ml) of brewed coffee -- don't appear to affect a woman's fertility. But one study did find that 200 mg or more of caffeine a day raise your risk of miscarriage.