Rocking, holding, feeding or otherwise fussing over a baby at bedtime may make the infant more likely to wake up during the night, researchers reported Friday.

A study of 122 mothers and their babies in Burlington, Mass., showed infants who had parents present when they fell asleep were significantly more likely to be troubled by frequent waking at night than those whose parents were not present at bedtime.About one-third of the mothers reported that a parent was routinely present when the baby went to sleep, while two-thirds said there was no parent around.

Overall, the babies, who ranged in age from 8 to 12 months, averaged about four "wakings" per week.

However, infants whose parents were present averaged about six "wakings" per week, compared with about three wakings per week among babies with no parent present at bedtime.

In addition, the prevalence of "frequent" waking at night - defined as seven or more waking incidents per week - was much higher among babies whose parents were present at bedtime, about 40 percent compared to 22 percent for those without a parent present.

The researchers from Boston City Hospital, Boston University School of Medicine and Public Health and Lahey Clinic Medical Center in Burlington, said waking at night is considered normal during a baby's first six months, but after then it is often regarded as a problem.

The researchers speculated that having parents around when a baby goes to sleep "establishes a learned association between parental presence and falling asleep."

Consequently, when a baby enters a natural period of rapid eye movement and arousal during the sleep cycle, the infant may be unable to return to deep sleep without a parent's presence because he or she has never learned to fall asleep alone.

Reporting in the journal Pediatrics, the researchers said their findings may have important practical implications "because if night waking is learned, then it may be unlearned . . . or even prevented."