Anonymous wrote:I'm not OP but I am interested in the explanation.
The research on sex imbalance in IVF has established that it exists, but is only able to guess at the explanation. For OE IVF, there is a 1 to 1.3 chance of conceiving a boy. For DE IVF, there is a 1 to 1.9 chance of conceiving a boy. The best explanation is that the selection criteria for how embryos are chosen for transfer causes the slight imbalance. The cells of male and female embryos divide at slightly different rates. Since a male embryo has slightly less genetic material to replicate, the cells divide slightly faster. So, by day 5 or 6, when the doctor is deciding which embryo to transfer, it is a little more likely that a male embryo will have the greatest number of cells. Since the cells of younger eggs divide faster in general, the imbalance is a little greater in DE IVF than in the overall OE IVF pool since, in general, the age of a donor is younger than the age of a woman doing IVF with her own eggs. It is also more common to do an eSET (elective single embryo transfer) with DE, so you are often choosing just the fastest doubling embryo instead of the fastest 2 or 3 embryos, increasing the importance of doubling time as a significant factor.
Our genetic counselor gave us the studies when we were doing DE IVF, but I think a Google search will easily pull up the actual studies if you are interested.