Some epidemiologic studies have suggested that the ingestion of CAFFEINE increases the risk of spontaneous abortion but the results have been inconsistent. Fetal loss is strongly related to tobacco smoking and heavy consumption of alcohol. The risk of spontaneous abortion was rather strongly proved to be associated with CAFFEINE intake. Records of smoking and CAFFEINE drinking were analysed as potential confounding variables in this study.About half of spontaneous abortions are chromosomal ones. This diversity allows application of two criteria to assess causality: (1) an association specific to a particular type of loss and (2) the time of exposure conception with pathogenesis. Exposure to CAFFEINE after conception cannot cause aberrations.In this control study case, 562 women with spontaneous abortion, all of 6 to 12 completed weeks of gestational age were considered and compared with 953 women with the same gestational age of no abortion. The relation between CAFFEINE consumption as well as spontaneous abortion and chromosomal aberrations search looked for any odds ratios for fetal loss was calculated for both high and moderate CAFFEINE consumption. Multivariate analysis was used to estimate the relative risks associated with the results. Among nonsmokers, more spontaneous abortions occurred in women who ingested at least 100mg of CAFFEINE per day than in women who ingested less than 100mg per day, with an increase in risk related to the amount ingested.Among smokers, CAFFEINE ingestion was not associated with an excessive of spontaneous abortion. When the analyses were stratified according to the results of karyotyping, the ingestion of moderate or high levels of CAFFEINE was found to be associated with an excessive risk of spontaneous abortion when the fetus had a normal or unknown karyotype but not during the fetal karyotype abnormality.These data suggest that CAFFEINE may be the responsible agent for fetal loss. Products such as coffee, tea, chocolate and cola beverages contain CAFFEINE. Therefore, it seems of value to inform both the scientific community and the consumer of the potential effects of excessive CAFFEINE consumption, particularly by pregnant women. This research documents an increased risk of spontaneous abortion associated with CAFFEINE consumption during pregnancy. However, overwhelming evidence indicates that CAFFEINE is not a human teratogen. More research is needed before unambiguous statements on the effects of CAFFEINE on pregnancy outcome variables can be made. Does the relation between fetal loss and CAFFEINE intake takes effect before pregnancy?