Research Article
Obstetrics.
Br Med J (Clin Res Ed) 1982; 285 doi: https://doi.org/10.1136/bmj.285.6356.1711 (Published 11 December 1982) Cite this as: Br Med J (Clin Res Ed) 1982;285:1711This is a PDF-only article. The first page of the PDF of this article appears above.