Erratum to: Arch Gynecol ObstetDOI 10.1007/s00404-010-1636-5The authors regret that a typographic mistake occurred inthe ‘‘Materials and methods’’ section of online publishedarticle. Instead of‘‘According to our prior analysis (N-Query advisor,Statcon, Witzenhausen, Germany), 33 patients in each armof the study were needed in order to achieve a power of80% with an a = 0.05.’’The correct sentence is‘‘According to our prior analysis (N-Query advisor,Statcon, Witzenhausen, Germany), 30 patients in each armof the study were needed in order to achieve a power of80% with an a = 0.05.’’