Abstract: Objective：To study the distribution of nanobacteria (NB) and explore an appropriate tissue as the source for detection of placental calcification infected with nanobacteria. Methods：The calcified placental tissues and umbilical cord blood from 20 pregnant women for isolation and culture of NB, and normal placental tissues were used as controls. The morphological identification of NB was performed with Gram and alizarin red staining and scanning electron microscope (SEM), transmission electron microscope (TEM). Results：The precipitates were corresponding to the characteristics of NB. The isolation rate of NB was 65% (13/20) in the specimens of calcified placental tissues and 80% (16/20) in the cord blood, and both of them were higher than that in normal placental tissues (10%) with a significantly statistical difference (chi-square values were 12.07 and 9.09 respectively, P<0.01), but there was no significant difference for the positive isolation rate of NB between the umbilical cord blood and calcified placental tissues (chi-square value was 1.33, P＞0.05). The shape of NB isolated from calcified placental tissue and umbilical cord blood under oil lens was spherical or rhabdoid with burr edge, and was globoid with size of 80-500 nm and staining of Gram-negative, Alizarin Red-positive under electron microscope. Conclusion：Nanobacteria infection may be relevant with placental calcification. The specimens from umbilical cord blood should be more suitable for detecting NB in calcified placental tissues.