[Vacuum extractors: description, mechanics, indications and contra-indications].

The vacuum extractor, as opposed to other instruments, does not increase the fetal head diameter for vaginal delivery. Introduced half a century ago, this device is today widely used in many countries probably because of a learning-curve which is acquired quicker than for the forceps. Major benefits obtained are the flexion of the fetal head provided that the cup is correctly placed, and the compulsory rotation induced that is most useful in the conversion of occiput posterior or transverse to anterior positions. The limitations reside in the need for maternal effort at expulsion and in the fact that it is unsuitable for face presentations. Moreover, like other instruments, the vacuum extractor can be harmful and even dangerous to the mother and her fetus. Therefore, its indications and contra-indications must be respected, and its operative use mastered with as much precision as for the forceps.