Sonography of the transverse fetal lie

Two hundred thirty-five patients with transverse fetal lies incidentally discovered by sonography at more than 20 weeks of gestation were followed to term. The overall persistence of this malposition was 6.0%, ranging from 2.6% in the 20-25 week group to 11.8% in the 36-40 week group. Low implantation or placenta previa was seen in 29.3% overall and 35.7% of cases that persisted to term. Other potentially predisposing anatomic factors were encountered infrequently. Most incidentally discovered transverse fetal lies seem to be fortuitous and transient, but the likelihood of persistence increases as term approaches.