P30.03: Ultrasonographic findings of placenta lacunae and lack of clear zone were frequently observed in placenta previa compared with normal placenta

It is well known placenta lacunae and lack of clear zone are ultrasonographic findings detecting for adherence of the placenta in placenta previa. However, these findings are occasionally observed in normal placentas. The purpose of the present study is to evaluate appearance of these findings in placenta previa compared with normal placenta. Ultrasonographic findings, including placenta lacunae and lack of clear zone, were prospectively observed in 70 cases with placenta previa. Similar to placenta previa, these findings were observed in cases with normal placentation. All subjects were delivered in our hospital between 2007 and 2009. A case-control study with 1:5 (350 controls) matched pairs was conducted to investigate these ultrasonographic findings. Each pair was matched for maternal age and frequencies of these findings were evaluated between placenta previas and controls. Placenta lacunae were observed in 31.4% and 9.7% cases with placenta previa and normal placenta (OR 4.2, 95% CI 2.3–7.9). Lack of clear zone were observed in 5.7% and 0.9% cases with placenta previa and normal placenta (OR 7.0, 95% CI 1.5–32.0). In cases with placenta previa 5 cases with adherence of the placenta were observed. Lack of clear zone were frequently observed in cases with adherences of the placenta compared to cases without them (60% vs. 1.5%; P = 0.001) in placenta previa, though frequency of placenta lacunae was not significantly different between with and without adherences of the placenta (60% vs. 29.2%). Similar to previous studies, lack of clear zone were strongly associated with adherence of the placenta. However, we should be aware of the fact that placenta lacunae and lack of clear zone were frequently observed in placenta previa even if adherences of the placenta were not complicated.