Ultrasonographic findings of placenta lacunae and a lack of a clear zone in cases with placenta previa and normal placenta

Objectives: To evaluate whether the frequencies of placenta lacunae and lack of a clear zone are higher in cases of placenta previa compared with those without it. Methods: Ultrasonographic findings just before delivery, including placenta lacunae and lack of a clear zone were prospectively evaluated in consecutive subjects. After collection, a case-control study with 1:5 matched pairs was conducted. The frequencies of ultrasonographic findings were analyzed in cases with placenta previa and normal placenta. Results: Seventy cases with placenta previa and 350 cases with normal placentas were observed. Five and zero cases with abnormal placental adherence were observed in cases with placenta previa and normal placenta, respectively. Lack of a clear zone was observed in 60 and 1.5% of cases with and without the placental adherence (p = 0.001). Placenta lacunae and lack of a clear zone were observed in 31.4 and 9.7% of cases with and without placenta previa [odds ratio (OR) 4.2]. Lack of a clear zone was observed in 5.7 and 0.9% of cases with and without placenta previa (OR 7.0). Conclusions: Placenta lacunae and lack of a clear zone are frequently observed in placenta previa even when there is no adherence of the placenta.