A baby's sleep may not suffer just because its mother likes a daily cup or two of coffee, according to a Brazilian study based on nearly 900 new mothers.
Studies over the years have come to mixed conclusions on whether caffeine during pregnancy was linked to increased risk of miscarriage or premature birth, but more recent studies have failed to show any heightened risk.
Not much was known, however, about whether caffeine during pregnancy or breastfeeding might disturb new babies' sleep - until the current study, published in Pediatrics.
The findings by Ina Santos and colleagues at Federal University of Pelotas, in Brazil, do not endorse heavy caffeine intake during pregnancy or breastfeeding, experts said, but are in line with research suggesting modest amounts may not pose a danger.
"Caffeine consumption during pregnancy and by nursing mothers seems not to have consequences on sleep of infants at the age of three months," wrote Santos and her colleagues.
The team interviewed 885 new mothers about caffeine intake and infants' sleep habits at the age of three months.
All but one said they drank caffeinated beverages during pregnancy. About 20% were considered heavy consumers of at least 300 milligrams a day. Just over 14% reported a heavy caffeine intake three months after giving birth.
Two hundred mg is about the amount in a 12-oz cup of coffee.
Overall, the researchers found no clear link between caffeine intake and the likelihood of reporting infant sleep problems.
Almost 15% of mothers said their three-month-old woke up more than three times each night, which was considered "frequent." But the odds were not statistically greater for the mothers who were heavy caffeine consumers.
"I think this report adds to the growing body of literature suggesting that moderate caffeine consumption during pregnancy is generally safe," said William Barth, chief of maternal-fetal medicine at Massachusetts General Hospital in Boston.
Barth, who was not involved in the study, chaired the committee at the American College of Obstetricians and Gynecologists (ACOG) that in 2010 wrote a report saying that 200 mg of caffeine a day probably did not carry pregnancy risks.
He said the bottom line for women is that moderate caffeine intake, up to a cup or two of coffee per day, seems safe during pregnancy, but that it is currently not known if there are adverse effects of higher levels of caffeine consumption.
As for breastfeeding, it is generally thought that 300 mg of caffeine or less each day is okay, said Lauren Hanley, an obstetrician at Massachusetts General.
That is the case for healthy, full-term babies, at least.
But preterm infants and newborns metabolize caffeine more slowly and may be more sensitive to the small amount of caffeine that passes into breast milk.
And studies suggest that high amounts of caffeine during breastfeeding - "much higher" than 300 mg a day - are related to fussiness and poor sleep in babies.