Women who drink eight or more cups of coffee daily while pregnant are at risk for spontaneous abortion and stillbirth, Danish researchers report. In their study, they found that fetal death was twice as likely among heavy coffee drinkers relative to pregnant women who did not drink coffee.

Adjusting for other risk factors weakened the association somewhat, but heavy coffee drinkers remained at 59 percent greater risk of fetal death, Dr. Bodil Hammer Bech of the University of Aarhus and colleagues report.

Women who drank four to seven cups daily had a 33 percent increased risk of fetal death.

“Due to our findings and previous studies we think it is reasonable to apply the precaution principle and advise pregnant women to abstain from drinking more than 3 cups of coffee per day,” said Bech. Denmark currently has an official policy warning women to restrict their coffee intake to three cups or less daily.

While a number of studies have linked coffee drinking to undesirable pregnancy outcomes, and there are plausible physiological mechanisms by which caffeine might harm a fetus, the risks of coffee drinking in pregnancy have been questioned, Bech and colleagues explain in the American Journal of Epidemiology.

To investigate, they surveyed 88,482 women enrolled in the Danish National Birth Cohort, among whom there were 1,102 fetal deaths. The women were interviewed about coffee intake and potentially confounding factors, such as alcohol consumption and smoking, at approximately 16 weeks’ gestation.

Among the women, 55.4 percent reported drinking no coffee during pregnancy, while 31.4 percent drank one-half to three cups daily. Thirteen percent of the women drank more than three cups of coffee daily, while 3.4 percent drank eight or more cups a day.

After adjustment, the researchers found, women who drank one-half to three cups a day had a 3 percent increased risk of fetal death; those who consumed four to seven cups had a 33 percent increased risk; and those who drank eight or more cups had a 59 percent greater risk of fetal death. The association was strongest for fetal deaths after 20 weeks gestation.

The researchers found no link between tea or cola consumption and fetal death, suggesting that caffeine may not be the exposure of interest. “Coffee contains a number of chemical compounds,” Bech noted. “Further studies should try to disentangle a caffeine effect from a non-caffeine effect.”

SOURCE: American Journal of Epidemiology, November 15, 2005.