The effect of maternal posture, meals and time of day on fetal movements.

During the last 3 to 4 months of their pregnancies, six healthy mothers provided a daily record of their own activity together with the amount of fetal movement. Fetal movement increased throughout most of the daytime to reach a peak in the evening. The mothers detected most movement when they were lying, less when they were sitting and least when they were standing. Later in the day the mothers were less likely to be standing and more likely to be sitting; when fetal movement was measured with the mother in the sitting posture, more movement occurred as the day progressed. Mealtimes did not have any effect upon movement. Some implications of these findings, both for the assessment of fetal well-being and for theories of the development of circadian rhythms in the infant, are discussed.