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 percent were considered heavy consumers of at least 300 milligrams a day. Just over 14 percent 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.