AbstractAfter 36 weeks gestation the placenta has a distinct echographic appearance which is characterized by rounded transonic areas measuring 1.5 to 4.5 cm. in diameter. Anatomic and histologic study of seven placentas with this echographic appearance has snown no abnormalities or characteristic findings. The recognition of the mature placenta is of clinical use in the determination of dysmaturity and growth retardation, where a single fetal head measurement may be misleading. The changes in the internal consistency of the placenta are most easily identified with a real‐time, water bath, linear scanner (Siemens Vidoson) but may also be seen with a compound contact scanner if non‐storage recording is emplo