Author Contributions: Drs Pasupathy and Smith had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Pasupathy, Wood, Smith.
Acquisition of data: Pell, Fleming.
Analysis and interpretation of data: Pasupathy, Wood, Pell, Smith.
Drafting of the manuscript: Pasupathy, Wood, Smith.
Critical revision of the manuscript for important intellectual content: Pasupathy, Wood, Pell, Fleming, Smith.
Statistical analysis: Pasupathy, Wood, Smith.
Obtained funding: Pasupathy, Wood, Smith.
Administrative, technical, or material support: Smith.
Study supervision: Wood, Smith.
Financial Disclosures: None reported.
Funding/Support: Dr Pasupathy is a recipient of a Clinical Research Training Fellowship awarded by the Medical Research Council and Royal College of Obstetricians and Gynaecologists (Florence and William-Blair Bell Memorial Fellowship Fund).
Role of the Sponsor: The funding source had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript.
Previous Presentation: Presented at the 28th Annual Scientific Meeting of the Society of Maternal Fetal Medicine; February 2, 2008; Dallas, Texas.