1. Dizygotic twin delivery following in vitro fertilization and transfer of thawed blastocysts cryopreserved at day 6 and 7 
E.Scott Sills, M.D., Cindy L Sweitzer, B.S., Paula C Morton, B.S., Mark Perloe, M.D., Carolyn R Kaplan, M.D., Michael J Tucker, Ph.D. 
Fertility and Sterility 
Volume 79, Issue 2, Pages (February 2003)
DOI: /S (02)

2. FIGURE 1
Post-thaw photomicrograph of three blastocysts cryopreserved on days 6 and 7, all of which implanted after embryo transfer. Following assisted hatching, blastocysts are reexpanding, with one actively hatching just before ultrasound-guided transfer (scale = 100 micron). The patient subsequently delivered dizygotic (female/female) twins.
Sills. Births after day 6 and 7 blastocyst cryopreservation. Fertil Steril 2003.
Fertility and Sterility  , DOI: ( /S (02) )