Effect of parity, gravidity, previous miscarriage, and age on risk of Down's syndrome: population based study.

We thank Christina Kelekun and Karen Wells for data entry and verification. The heads of the cytogenetic laboratories of England and Wales and the Association of Clinical Cytogeneticists provide continued support and data. Contributors: EA was the grant holder and director of research and contributed in discussion and to the drafting of the manuscript; she is guarantor for the study. RGI was responsible for the development and efficiency of the coding and data entry for the register from 1989 to 1997. DM was project coordinator and cytogeneticist for the register with responsibility for analysing the data and writing the manuscript. Funding: The register was initially funded by the Medical Research Council; since 1994 it has been funded by North and South Thames NHS Research and Development. Conflict of interest: None.