Eye movement activity in normal human fetuses between 24 and 39 weeks of gestation

Rapid eye movement (REM) sleep occurs throughout a relatively large proportion of early development, and normal REM activity appears to be required for healthy brain development. The eye movements (EMs) observed during REM sleep are the most distinctive characteristics of this state. EMs are used as an index of neurological function postnatally, but no specific indices of EM activity exist for fetuses. We aimed to identify and characterize EM activity, particularly EM bursts suggestive of REM periods, in fetuses with a gestational age between 24 and 39 weeks. This cross-sectional study included 84 normal singleton pregnancies. Fetal EMs were monitored using real-time ultrasonography for 60 min and recorded as videos. The videos were manually converted into a time series of EM events, which were then analyzed by piecewise linear regression for various EM characteristics, including EM density, EM burst density, density of EMs in EM bursts, and continuous EM burst time. Two critical points for EM density, EM burst density, and density of EMs in EM bursts were evident at gestation weeks 28–29 and 36–37. Overall EM activity in human fetuses increased until 28–29 weeks of gestation, then again from 36–37 to 38–39 weeks of gestation. These findings may be useful for creating indices of fetal neurological function for prognostic purposes.

快速眼动（REM）睡眠在发育早期占据相对较大的比例，健康的大脑发育似乎需要正常的快速眼动活动。快速眼动睡眠期间观察到的眼动（EMs）是该睡眠状态最具特征性的表现。眼动常被用作产后神经功能的评估指标，但目前尚无针对胎儿的眼动活动特异性评估指标。本研究旨在识别并表征胎龄24至39周胎儿的眼动活动，尤其是提示快速眼动周期的眼动爆发。本横断面研究纳入84例正常单胎妊娠。通过实时超声监测胎儿眼动60分钟并录制视频，研究人员手动将视频转换为眼动事件的时间序列，随后采用分段线性回归分析多项眼动特征，包括眼动密度、眼动爆发密度、眼动爆发内眼动密度及连续眼动爆发时长。结果显示，眼动密度、眼动爆发密度与眼动爆发内眼动密度在胎龄28~29周及36~37周存在两个关键转折点。人类胎儿的整体眼动活动在胎龄28~29周前持续升高，随后在36~37周至38~39周再次呈现上升趋势。上述发现或可用于构建胎儿神经功能评估指标，以服务于预后评估目的。