P043 Comparison of sleep position classification between neck and abdominal placement in late pregnancy

BACKGROUND: Going to sleep in the supine position during pregnancy is associated with an increased risk of stillbirth, however objective sleep position data are needed to verify the mechanisms of this relationship. Sleep position measurement devices are typically worn at the neck or chest, but abdomen position is more important for assessing impact of the gravid uterus on inferior vena cava compression. This study aimed to compare sleep position measured at the neck versus the abdomen in late pregnancy. METHODS: Twenty women in the third-trimester of pregnancy wore the Night Shift Sleep Positioner with both the neck band and abdominal band for one night. Position classified as left, supine, right, prone and upright was recorded in 30-second epochs and compared across device locations. RESULTS: There was substantial agreement between the neck and abdomen for determination of all sleep positions with 88% concordance on an epoch-by-epoch basis (κ = .797 [SE .006], p<.001). However, agreement was only fair (κ = .407 [SE .007], p < .001) for supine versus non-supine positioning, with a trend for more supine sleep using the neck device compared to the abdomen (47.5 [16.3,80.5] vs 19.0 [6.8,83.8] minutes, median difference =7.3 [0.5,39.3], p=.12). The average absolute supine difference across device locations was 30.8 minutes [4.0,65.3]. CONCLUSION: Position measurement at the neck and abdomen has considerable concordance on an epoch-by-epoch basis, however agreement was reduced when comparing supine position only. Site of sleep position measurement in pregnancy has implications for assessing supine positioning, intervention success and stillbirth risk.