Vandenberghe G., Vierin A., Bloemenkamp K., Berlage S., Colmorn L., Deneux-Tharaux C., Donati S., Gissler M., Knight M., Langhoff-Roos J., Lindqvist PG., Maier B., van Roosmalen J., Zwart J., Roelens K., INOSS (the International Network of Obstetrics Survey Systems) None.