PRENATAL HEAD POSITION FROM 12-38 WEEKS .2. THE EFFECTS OF FETAL ORIENTATION AND PLACENTAL LOCALIZATION

The possible influence of placental localization and fetal orientation on a predominant fetal head position was studied longitudinally in 10 uncomplicated pregnancies from 12 to 38 weeks by means of real-time u ltrasound. Throughout gestation, when the fetal vertebral column was o rientated to the left side of the mother, head positions to the right and in midline were seen most frequently, whereas a vertebral column t o the right was more often associated with a head left position and a head position in midline. These findings support the suggestion that w hen the fetal vertebral column is in a lateral orientation relative to the mother, one side of the fetal head is more likely to be restricte d by the pelvis and backbone of the-mother. However, the orientation o f the fetal vertebral column does not seem to be a determining factor as the incidence of lateralized head positions increased with age, whi le the incidence of a vertebral column to the right or left side of th e mother remained unchanged, No associations were found between the lo calization of the placenta and either head position or fetal lie.