Fetal movement signals and maternal artifacts.

<p>The heavy blue lines at the bottom indicate fetal movement identified by the automated analysis software. The heavy red lines indicate rejections. The two upper lines show maternal movement. The two lower lines show fetal movement. For each pair, the upper line is from the accelerometer after passing the filters, and the lower line is the modification (integral). One grid mark indicates one second with 20 or 60 seconds per screen. <b>A:</b> This shows fetal movement and the influence of the maternal heartbeat in the FM channel (29 yrs, 32 gestational weeks). Since there is no movement by the mother, the signals on the FM channel are recorded as fetal movement. <b>B:</b> This shows maternal movement influencing the fetal movement channel. In this case (29 yrs, 32 gestational weeks), the signals on the FM channel include both maternal and fetal movements, so the maternal movement is excluded by the software. <b>C:</b> This shows periodic leg movements by a mother (26 yrs, 24 gestational weeks) and their influence on the fetal signal. Here the mother (upper two lines) has periodic leg movement at intervals of 20 to 40 seconds. The screen shows 60 seconds. Two (thigh) movements are seen in the top line for the mother. They influence the abdomen through vibration, reflected in the modified signal (integral) shown in the second line. In cases such as this, the mother's body movement signals can be removed by the analysis software.