Significant differences were elicited when comparing days until HCG injection ( 15.0 1.7 versus 12.0 1.9 , p = 0.91 ) , endometrial thickness ( mm ) ( 8.5 1.9 versus 12.5 1.9 , p < 0.001 ) , serum levels of mid-luteal and midcycle estradiol ( p < 0.001 ; Figure 2 ) , LH ( IU/ml ) ( p < 0.001 ) as well as mid-luteal progesterone ( p < 0.001 ) .