2. Materials and methods A cross-sectional prospective surveillance study was conducted be- tween July 1, 2009, and June 30, 2010, at 27 referral obstetric units locat- ed throughout Brazil. An investigator and a coordinator were present at each center.
2. Materials and methodsA cross-sectional prospective surveillance study was conducted be-tween July 1, 2009, and June 30, 2010, at 27 referral obstetric units locat-ed throughout Brazil. An investigator and a coordinator were present ateach center.