The fetus is in a transverse lie when its longitudinal axis is perpendicular to the long axis of the uterus. A transverse lie can occur in either of two configurations:
●The curvature of the fetal spine is oriented upward (also called "back-up" or dorsosuperior), in which case the fetal small parts present at the cervix.
●The curvature of the fetal spine is oriented downward (also called "back-down" or dorsoinferior), such that the fetal shoulder presents at the cervix (figure 1).
Transverse fetal lie occurs in approximately one in 300 deliveries [1,2]. In contrast, the fetus is often found in a transverse lie when ultrasound examination is performed early in gestation .
Most fetuses in transverse lie early in pregnancy convert to a cephalic (or breech) presentation by term. The later in pregnancy the transverse lie is diagnosed, the more likely it is to persist. This was illustrated in a series of 235 patients with transverse fetal lie incidentally discovered by sonography at more than 20 weeks gestation . When the diagnosis was first made between 20 to 25 weeks of gestation, 2.6 percent persisted as transverse lie at term. By comparison, when the diagnosis was first made at 36 to 40 weeks, 11.8 percent persisted to the time of delivery.