. Author manuscript; available in PMC: 2012 Nov 28.
Published in final edited form as: Obstet Gynecol. 2012 Jul;120(1):83–90. doi: 10.1097/AOG.0b013e318258fbde
© 2012 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams & Wilkins.