. Author manuscript; available in PMC: 2013 Aug 16.
Published in final edited form as: Obstet Gynecol. 2010 Dec;116(6):1257–1264. doi: 10.1097/AOG.0b013e3181fb540f
© 2010 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams & Wilkins.