Aetiology and management of the secondary brow

The finding that a brow presenting within the pelvic cavity in the mento-anterior position during the second stage of labour could be easily and safely delivered by means of Kielland's forceps rotation and extraction led to a search for the cause of this rare phenomenon since normally brows are associated with non-engagement of the head. A personal series of six cases, collected over 39 years, were studied. Particular attention was paid to pelvic size and shape with detailed X-ray pelvimetry being obtained in the puerperium from the latter three patients. In all cases the pelvises were found to be commodious and, in the three where X-ray pelvimetries were taken, they were found to be anthropoid in shape, which is known to favour the occipito-posterior position. Past and subsequent pregnancies conducted by the author were in every instance associated with an occipito-posterior position, and a mechanism of labour for secondary brow presentations until impasse occurred was suggested. It was concluded that the condition only occurred when the pelvis was roomy and anthropoid in shape, and, for those experienced in their use, Kielland's forceps rotation and extraction was preferable to caesarean section. Furthermore, aficionados of the ventouse were warned to avoid attempting delivery with that instrument for such would be doomed to failure.