The UK's Human Fertilisation and Embryology Authority has published documentation that more women who are 40 years of age and older are making use of fertility treatment.
The stats show a ten-fold boom from 1991 to 2006.
In this related article for The Guardian, there's evidence of some ongoing debate about how fertility treatment is or should be presented as a solution for women of "advanced maternal age" (a term none too pleasing to the ear...)
Agreement seems to be that the increase in older mama-wanna-be's is not so much a result of new or better technology, but of things like financial ability to afford treatment coupled with an apparently growing number of women who are making the conscious life choices -- like putting off motherhood for careers, etc. -- that wind up impacting their fertility negatively.