Except in severely premature fetuses (in which a transverse lie may deliver vaginally), a persistent transverse lie cannot deliver spontaneously, and if uncorrected, impaction takes place (Fig. 26-3A). The shoulder is jammed into the pelvis, the head and breech stay above the inlet, the neck becomes stretched, and progress is arrested.
Spontaneous version takes place occasionally, more often with oblique than with transverse lies. Before or shortly after the onset of labor, the lie changes to a longitudinal one (cephalic or breech), and labor proceeds in the new position. Unfortunately, the chance of spontaneous version occurring is small, too small to warrant more than a very short delay in instituting corrective measures.
Neglected transverse lie results from misdiagnosis or improper treatment. At first, the contractions are of poor quality, and the cervix dilates slowly. Because of the irregularity of the presenting part, the membranes rupture early, and the amniotic fluid escapes rapidly. As the labor pains become stronger, the fetal shoulder is forced into the pelvis, the uterus molds itself around the baby, a state of impaction ensues, and progress is halted. From this impasse, there is one of two outcomes:
Uterine rupture: Labor goes on. The upper part of the uterus becomes shorter and thicker, and the lower segment becomes progressively more stretched and thinned until it ruptures
Uterine inertia: The uterus becomes exhausted, and the contractions cease. Intrauterine sepsis sets in and may be followed by generalized infection
In either event, fetal death is certain and maternal mortality possible. Transverse lies must not be neglected!
Because the presenting part does not fill the inlet, the membranes tend to rupture early and may be followed by prolapse of a fetal arm or the umbilical cord (Figs. 26-3B and C). Both are serious complications necessitating immediate action.