Feb. 20, 2003 -- Overindulging in coffee and caffeine during pregnancy can pose significant risks to an unborn baby. A new study shows pregnant women who drink more than eight cups of coffee a day are more than twice as likely to suffer a stillbirth compared with women who don't drink coffee during pregnancy.
Researchers say exposure to caffeine during pregnancy has already been linked to an increased risk of spontaneous abortion and low birth weight, and animal studies have suggested that large amounts of caffeine raise the risk of stillbirth in monkeys. But until now it hasn't been clear what role caffeine alone plays in stillbirth risk because other lifestyle factors associated with heavy coffee drinking, such as smoking or drinking alcohol, may also increase the risk of stillbirth or infant death within the first year of life.
To examine these effects, Danish researchers looked the medical history, smoking habits, and alcohol and coffee consumption of 18,478 pregnant women during 1989-96 and compared these records with the rates of stillbirth (delivery of a dead fetus after 28 weeks gestation) and infant death within a year after birth.
They found the risk of stillbirth actually decreased slightly among women who drank one to three cups of coffee per day, but then increased with the number of cups of coffee per day the woman drank during pregnancy.
"Compared with women who did not drink any coffee, women who drank four to seven cups a day had an 80% increased risk of stillbirth, and women who drank eight or more cups a day a 300% increased risk," write researcher Kirsten Wisborg, of the perinatal epidemiological research unit at Aarhus University Hospital in Aarhus, Denmark, and colleagues.
Their findings appear in the Feb. 22 issue of the British Medical Journal.
Researchers say women with a high intake of coffee were also more likely to have a high intake of alcohol and be smokers. Once they adjusted for smoking habits and alcohol drinking during pregnancy, the risk of stillbirth associated with coffee consumption decreased slightly to about a 40% increase in risk for those who drank four to seven cups of coffee per day and a 220% increase in risk among those who drank more than eight cups a day.
After these adjustments, the study also found no significant link between coffee consumption and the risk of infant death within the first year of life.
Overall, the researchers say that when it comes to increasing stillbirth risk, their study suggests that there is a threshold effect around four to seven cups of coffee per day. They say there did not seem to be one single reason that could explain the increased risk of stillbirth found among women who consumed large amounts of coffee.
SOURCE: British Medical Journal, Feb. 23, 2003.