Fetal breathing and behavior measured through a double-wall Plexiglas window in sheep

Area of Science:

• Veterinary Science
• Developmental Biology
• Neuroscience

Background:

• Assessing fetal behavior in utero is challenging due to the inability to directly observe the fetus.
• Previous studies lacked direct visualization of intrauterine fetal behavior and sleep states.

Purpose of the Study:

• To investigate and characterize fetal behavior, including sleep patterns, breathing, and swallowing, in ovine fetuses.
• To compare intrauterine fetal behavior with postnatal behavior to identify distinct developmental stages.

Main Methods:

• A Plexiglas window was surgically implanted in the flank of ewes to allow direct observation of fetuses.
• Fetuses were instrumented to measure electrocortical activity (ECoG), breathing, and swallowing.
• Intrauterine behavior was recorded and later compared to postnatal behavior after delivery.

Main Results:

• Ovine fetuses exhibited distinct sleep states: quiet sleep (high-voltage ECoG) and active sleep (low-voltage ECoG).
• Quiet sleep was characterized by minimal movement, rare eye/breathing movements, and absence of swallowing.
• Active sleep involved increased movements, prominent breathing, and swallowing activity.
• Fetal wakefulness, defined by open eyes and purposeful head movements, was observed postnatally but not in utero.

Conclusions:

• Fetal sheep demonstrate organized sleep-wake cycles in utero, differing from postnatal behavioral states.
• The specific definition of wakefulness used postnatally could not be demonstrated in the intrauterine environment.
• Direct observation via surgical window provides novel insights into prenatal behavioral development and sleep physiology.