Pregnant and nursing women who consume caffeine aren't causing their babies to wake up at night, a new study says.

The study involved 885 infants born in 2004 in Brazil, and the results showed that while babies of moms who were heavy consumers of caffeine were slightly more likely to wake frequently during the night compared with babies of moms who drank much less caffeine, the effect was small enough that it may have been due to chance differences between the groups.

"Maternal caffeine consumption, even in large amounts during gestation and lactation, had no consequences on sleep of the infant at 3 months of age," the researchers wrote in their conclusion.

The findings are published online today (April 2) in the journal Pediatrics.

Previous studies have linked heavy caffeine consumption during pregnancy with an increased risk of miscarriage, though findings have been mixed. According to guidelines from the American Academy of Pediatrics, caffeine is safe for breast-feeding women in moderate amounts (defined as two to three cups of coffee a day).

During infancy, nighttime waking is common. The researchers looked to see whether heavy caffeine consumption by women during their pregnancy and after giving birth was linked with more frequent night waking in babies.

For their study, the researchers at the Federal University of Pelotas interviewed mothers shortly after they gave birth, and examined their babies. Three months later, the mothers were interviewed again about their babies' sleep habits over the previous 15 days.

Those babies who woke more than three times a night, on average, were considered to have frequent night wakings. The researchers also collected samples of coffee from the women's houses to measure the caffeine content.

Nearly 20 percent of the mothers were heavy consumers of caffeine, meaning they drank more than 300 milligrams per day (the equivalent of about three or four cups of home-brewed coffee) daily, and about 14 percent of the babies woke three or more times, on average, during the night.

The reason there was no link between moms' caffeine habits and babies waking up at night is not clear, but it may be that babies born to mothers who heavily consume caffeine develop tolerance to it, according to the study.

Still, differences in people's sensitivity to the stimulant are not well-understood, the researchers said. Genetics and the development of tolerance may both a role in the extent to which caffeine disrupts sleep.

"This study revealed that prevalence of caffeine consumption is almost universal during pregnancy," the researchers noted. Only one woman in the study reported no caffeine consumption during pregnancy.

Pass it on: Caffeine consumption by pregnant women and nursing mother's doesn't contribute to their babies waking up at night.

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