Degenerative spondylolisthesis is most common at the L4/L5 level and in women.

There are several possible reasons for its predilection at this site, but there is no satisfactory explanation for the predominance in women.

We considered that pregnancy was a possible influence.

We reviewed the records and radiographs of 949 women and 120 men aged 50 years and over who had attended a spinal surgeon for low back pain over a five-year period.

We found that women who had borne children had a significantly higher incidence of degenerative spondylolisthesis than nulliparous women (28% v 16.7% ; p=0.043).

The men had a 7.5% incidence, significantly less than nulliparous women (p=0.031).

Our results suggest that pregnancy is an important factor in the aetiology of degenerative spondylolisthesis.