Aim: Approximately two-thirds of term vertex fetuses are in the left occiput position in utero. However, little is understood about the physiology of maternal-fetal positioning during pregnancy. It was hypothesized that fetal left occiput positioning is affected by maternal positioning. The present study was designed to investigate the relationship between maternal positioning in late pregnancy and fetal positioning in utero.
Methods: A prospective cohort study was conducted at Ueda Hospital, Kobe, Japan. Eligible women were limited to low-risk pregnancies ending in spontaneous vaginal delivery with singleton vertex fetuses. Information obtained from the mother included the preference of positioning during sleep in the second half of pregnancy. Fetal information recorded after delivery included fetal positioning.
Results: Eighty-one (50.6%) of 160 evaluated women preferred left lateral positioning while 70 (43.8%) women preferred right lateral positioning in the second half of pregnancy. Seventy-seven (51.7%) of 149 evaluated fetuses were in the left occiput position while 72 (48.3%) fetuses were in the right occiput position in utero. Maternal left lateral positioning with fetal left occiput position in utero was the predominant positioning (41 of 149, 27.5%). However, there was no statistical relationship between maternal positioning and fetal occiput positioning in utero.
Conclusion: More women prefer the left lateral position during the second half of pregnancy. More fetuses are in the left occiput in utero during the late stage of pregnancy. However, no statistical relationship was observed between maternal and fetal positioning.