What are the disadvantages of using PGD?
Yes, there are some.
PGD will add about $3,000 to the cost of an IVF cycle. Your cost may vary depending if you test only for sex determination, or add additional testing for chromosomal abnormality as well (see types of PGD testing.)
Unfortunately, some embryos will not survive the cell biopsy, and will perish after the procedure. A perfectly healthy embryo that may have implanted, without undergoing PGD, is instead lost. If you wind up with very few embryos, it may be recommended to skip PGD, because you could turn out to have no embryos to survive the cell biopsy.
Misdiagnosis with PGD
This does not refer to gender, but in diagnosing embryos as chromosomally normal or abnormal. PGD has about a 2% "false normal" rate, meaning that an embryo identified as normal may actually have an abnormality; and a 5% "false abnormal" rate, meaning that an embryo identified as abnormal, and discarded, was in fact normal.
Many people are opposed to the use of PGD for the use of sex selection, because healthy, normal embryos are discarded just for being the "wrong" sex. PGD's inventor, Mark Hughes, says he developed the technique to prevent disease, and "the last time I checked, your gender is not a disease."
See: Gender Selection Ethics.