Group 1 ( GPG+P 4 ; n = 330 ) , received gonadotrophin-releasing hormone ( GnRH ) I/M on Day 0 , a progesterone ( P4 ) - releasing intravaginal device from Days 0-7 , prostaglandin F2 ( PGF ) I/M on Day 7 and a second dose of GnRH at the time of FTAI on Day 9 .