Lechatchilah one should be careful not to interrupt between the birchas erusin and the act of kiddushin. Because of this, R’ Moshe Sternbuch (Shu”t Teshuvos V’Hanhagos 4:287 s.k. 8) writes that the chosson should designate witnesses before the birchas erusin, to avoid making unnecessary interruptions between the berachah and the act of kiddushin. And some say that it is also best that the mesedar kiddushin asks the chosson the questions he asks about the ring and the witnesses before the birchas erusin (Tel Talpiyos, Kovetz 64, pg. 60).
Although lechatchilah one should avoid making unnecessary interruptions between the birchas erusin and act of kiddushin, the Shu”t Noda B’Yehudah (Even HaEzer, siman 81) speaks out clearly that even if there is an interruption unrelated to the act of kiddushin, we don’t repeat the birchas erusin.
