A new study found that pregnant women using their cellphones are disturbing the sleep-and-wake cycles of their fetuses.

According to the American Pregnancy Association, a fetus has developed a sleep-and-wake cycle during the beginning of the third trimester. Fetuses spend up to 95 percent of their time sleeping, either in deep sleep or light sleep.

However, a study conducted by researchers at Wyckoff Heights Medical Center in New York City found that some fetuses are not getting the right amount of sleep because of their mother's constant use of mobile devices. The finding provided insight into how cellphones cause fetal reactions, suggesting that the sleeping fetuses are being awoken from their sleep.

"We wanted to see what these devices can do to the fetus," Dr. Boris Petrikovsky, study co-author and professor of obstetrics and gynecology, and director of maternal and fetal medicine at Wyckoff Heights Medical Center in New York City, told HealthDay News.

"And actually what we figured out is that if you're a baby in-utero [in the womb] and someone wakes you up every hour, you will not be a happy camper. The sound, and perhaps even vibrations, cause a lot of 'startle reflex', which disturbs the normal sleep cycle," he said.

The study involved 28 pregnant women who were all in their third trimester. They were given cellphones that were purposely activated to ring in five-minute intervals. The participants underwent ultrasound screening while the cellphones were ringing to see the fetuses' reactions.

The experiment showed that the fetuses were startled when the cellphones rang. The researchers observed that the fetuses were turning their heads, opening their mouths, and blinking. However, they also seemed to get accustomed to the sounds as weeks passed by.

The researchers admitted that further research is needed because they weren't certain whether the disturbed sleep-and-wake cycles of the fetuses have negative effects on the babies, according to HealthDay News.

"We can't say that this is definitely causing the higher pregnancy risk that has been seen," Petrikovsky added. "But we can say for sure that cycles of normal fetal behavior are definitely disturbed or interrupted by the frequent use of cellphones and beepers."

The study will be presented in the annual meeting of the American Congress of Obstetricians and Gynecologists in San Francisco this week.