embryo selection

[biology_06er]

Hi,

I've been reading about analyzing culture medium with regards to embryo selection using technqiues such as metabolmoics and I'm kinda confused...so I read that what they did was they compared the media of successful and not-succesful pregnancies and compared the spectra to see the differences etc...so this is done AFTER the pregnancy has occured...if it was to be used before embryo selection how would one go about testing...would they simply test all the media (like say take a drop or two of media) that the embryos are developing in-in vitro and then implant the "good ones"??

Hope you get where I'm going with this question,
Thanks,
b_06er