Researchers from the Fertility Clinic of Aarhus University Hospital in Denmark, who studied nearly 4,000 IVF and ICSI patients, described the adverse impact of coffee consumption as “comparable to the detrimental effect of smoking”.
Results showed that the consumption of five or more cups of coffee a day reduced the clinical pregnancy rate by 50% and the live birth rate by 40%.
“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 Dr Ulrik Schiøler Kesmodel, who led the study.
How the research was conducted
The study, performed in a large public IVF clinic, was a prospective follow-up of 3,959 women having IVF or ICSI as fertility treatment. Information on coffee consumption was gathered at the beginning of treatment (and at the start of each subsequent cycle). The statistical analysis controlled for variables such as female age, female smoking habits and alcohol consumption, cause of infertility, female body mass index, ovarian stimulation, and number of embryos retrieved.
The analysis showed that the “relative risk” of pregnancy was reduced by 50% in those women who reported drinking five or more cups of coffee per day at the start of treatment – and the chance of live birth was reduced by 40% (though this trend was not quite statistically significant). No effect was observed when the patients reported coffee consumption of less than five cups.
“No harmful effects of coffee at lower levels of intake”
Not wishing to worry IVF patients unnecessarily, Dr Kesmodel emphasised that the study found no harmful effects of coffee at lower levels of intake.
This result, he said, “is well in line with previous studies on time-to-pregnancy and miscarriage, which also suggest that, if coffee does have a clinically relevant effect, it is likely to be upwards from a level of four-to-six cups a day.”
Dr Kesmodel concluded that based on the results of the study, it “seems reasonable” that women should not drink more than five cups of coffee a day when having IVF.
