Critical evaluation of methods for electron microscopy of cervical mucus

The ultrastructure of cervical mucus has been studied by scanning (SEM) and transmission (TEM) electron microscopy. The images differ according to the methods used for preparation; different patterns were found in the same sample when the freeze-drying and critical point-drying methods were used for SEM. When using TEM, the specimen appeared more homogeneous, with fine fibrils and granules. This accords with the theory that the cervical mucus consists of a randomly entangled fibrillar network. Electron microscopy of cervical mucus requires preparation procedures which involve considerable risk of creating artefacts. In our experience the TEM technique produces fewer artefacts and therefore gives pictures more true to the in vivo situation.