As a procedure that was first performed in 1989, pre-implantation genetic diagnosis (PGD) has been a breakthrough in helping couples at risk of carrying life-threatening genetic diseases to avoid passing such afflictions to their offspring.

PGD can be used only in conjunction with in vitro fertilization (IVF). Because IVF allows examination of an embryo outside the womb, specialists can take sample cells for analysis and possible detection of known genetic diseases or chromosomal abnormalities. This allows genetics experts to identify embryos with irregularities; then the physician can transfer only non-affected embryos for uterine implantation, increasing the probability that couples will have healthy babies.

While PGD has been used in treating women with recurring miscarriages in hopes of identifying embryos with normal chromosome structure and number for implantation, the effectiveness of this approach is a topic of ongoing debate and research.

But the effectiveness of PGD for genetic screening is unquestioned and increasing. Prior to PGD, the diagnosis of genetic disease was limited to testing a fetus through amniocentesis or chorionic villus sampling (CVS), in which cells from the placenta are sampled and tested early in a pregnancy. In contrast, PGD provides a couple with more conclusive information before the embryo becomes a fetus.

A couple who knows the genetic health of an embryo has the tools to make more informed decisions about how to proceed.