Researchers say the results show that crying may represent a fifth, previously unknown behavioral state for human fetuses. Previously recognized behaviors in unborn fetuses include quiet sleep , active state, quiet awake, and active awake.

Video-recorded ultrasound images of third trimester fetuses show that they appeared startled in response to a low-decibel noise played on the mother's abdomen and display crying behavior, such as opening their mouths, depressing their tongues, and taking several irregular breaths before exhaling and settling back down again.

New research shows that fetuses may learn to express their displeasure by crying silently while still in the womb as early as in the 28th week of pregnancy .

Sept. 13, 2005 -- A baby's first cry may happen in the womb long before its arrival in the delivery room.

Babies May Cry in Womb

In a report published in the current issue of the Archives of Disease in Childhood, researchers describe stumbling upon the finding while researching the effects of tobacco and cocaine on pregnancy for another purpose.

In that study, researchers observed the response of third-trimester fetuses of mothers who used cigarettes or cocaine during pregnancy to a soft sound played on the mother's abdomen.

During the course of the study, they found that several of the fetuses appeared to cry in response to the disruption.

For example, one video clip shows a female fetus turning her head, opening her mouth, depressing her tongue, and letting out a single short breath followed by a deep inhalation and exhalation in response to the sound. Then the fetus tightens her chest and lets out three quick breaths accompanied by a quivering chin and increasing head tilt.

Researchers say this crying response was found in 10 fetuses belonging to four mothers who smoked cigarettes during pregnancy, three who smoked and used cocaine, and three who neither smoked nor used cocaine, suggesting that these behaviors are not specific to tobacco or cocaine exposure.

They say documenting crying behavior in third-trimester fetuses may have developmental implications because crying is a complex behavior that requires coordination of various motor systems. It also requires reception of a stimulus, recognizing it as negative, and incorporating an appropriate response.