Not just Pre-Implantation Genetic Screening, but also post-screening genetic manipulation of the embryo, inserting non-native sequences (making mathematical and musical intelligence more probable). Also, the fate of the unused zygotes.
Please pardon the video quality, this resolution is as-is on the DVD. The footage was never cleaned up for release by the makers, and this take was not used in the theatrical version - IMHO, a wise choice, as it changes the emotional significance of what is being done.
"Keep in mind, this child is still you - simply the best of you. You could conceive naturally a thousand times, and never get such a result."