We have 2 Day 3 frozen embryos. Should we do a Day 3 transfer ? or a Day 5 transfer ?

A patient send me this email

Hi , We are trying our best to absorb the emotional trauma after going thru 1st failed IVF cycle.  We have gone for ICSI . All 5 eggs fertilised all are of grade A . The lab took 3 of them to blastocyst stage. 2 reached Day 5 and were transferred in a frozen cycle. Unfortunately this resulted in a BFN. We are left with 2 day 3 8-cell grade A embryos, and we are going for FET this month.. Should we try to take them to blasto stage , or should we transfer them as day 3 embryos. We are very confused now and upset - please help , as I love reading your articles.. 

I feel you should grow them to Day 5 before transferring. Yes, there is a risk they may stop growing in vitro, which means you may end up with no embryos to transfer, but if the embryos are going to arrest, it's best they do so in the lab, rather than in your wife's uterus ! What's the point of making your wife go through a traumatic 2ww  ?

Best of luck !