If you’ve ever undergone an embryo transfer during a round of in vitro fertilization (IVF), you’ve probably felt like you’re made of glass – that you don’t want to do anything that could risk the embryo (or embryos) implanting and growing into a healthy baby. In short, in this situation, a miscarriage is obviously what a woman fears most.
While a lot to do with miscarriage is simply a mystery, a new study reported in Reproductive BioMedicine Online has shed some light on what increases the chances of a lost pregnancy following an embryo transfer during IVF. Researchers looked at data from nearly 53,000 pregnancies in Australia and New Zealand between 2004 and 2008 and found that while a woman’s age and her obstetric history (meaning, especially, if she's miscarried before) are most important in estimating miscarriage risk, the scientists noted that “the transfer of fresh embryos is associated with fewer miscarriages than the transfer of frozen-embryos,” wrote ScienceDaily.com, in a report on the study.
Other findings from the study: Women were less likely to miscarry if they had transferred one embryo, versus two, and also had better odds for avoiding a miscarriage during a frozen-embryo transfer when an embryo was frozen early in its development.
This led the researchers to propose that more doctors might try transferring fresh embryos at the blastocyst stage (when the embryo is the hollow ball of cells that begins to form around days 4 to 6 following fertilization) and freezing embryos that have reached the cleavage stage, in which the cells in the embryo divide and create new cells at about days 2 to 4 after fertilization, to reduce the chances of miscarriage. Whether this approach would in fact lower miscarriage rates needs to be studied, though.