Dominant maternal sleep position influences site of placental implantation

The objective of this study was to determine if maternal sleeping position around the time of implantation influences eventual placental implantation site. Between November 1997 and April 1999, women with singleton pregnancies between gestational ages of 15 and 20 weeks presenting for ultrasound examinations were prospectively queried regarding their usual position of sleep during early gestation. Dominant position of sleep was noted as prone, supine, right side, or left side. At ultrasound examination, placental location was categorized as (1) fundal, (2) left high, (3) right high, (4) anterior high, (5) posterior high, (6) anterior low, (7) posterior low, (8) right low, (9) left low, or (10) central low. During the 18 months of this study, data were obtained from 1,500 patients. At the time of conception, front or prone sleeping was the most common (497 of 1,500, 33.1%), followed by right side (439 of 1,500, 29.3%) and left side (360 of 1,500, 24%), with the back being the least frequent position of sleep (204 of 1,500, 13.6%). Women who usually slept supine at the time of conception and implantation were significantly more likely to have a high or fundal placental location compared with those who usually slept in the prone position (p = 0.041). In addition, women who slept exclusively on their right side early in pregnancy were significantly more likely to have a right-sided placental location compared with women who slept exclusively on their left side (p = 0.025). The data from this investigation indicate that sleeping position early in gestation may influence the ultimate placental implantation site.