Does using 2 vials of sperm per Intrauterine Insemination (IUI) attempt increase the chance of pregnancy?

Question

I read on https://community.cryobank.com/discussion/3305/how-many-vials-per-iui that some reproductive endocrinologists (RE) recommend to use 2 vials of sperm per Intrauterine Insemination (IUI) attempt to increase the chance of pregnancy, for example:

Do they always use 1 per IUI? I had read somewhere that if you wanted to use 2 to increase your chances, that was an option-?

and

My RE only uses 1 vial per IUI but I have heard of other places that use 2. I don't know if it is an option but you could definitely discuss it with your doc to see what he/she prefers.

Does using 2 vials of sperm per Intrauterine Insemination (IUI) attempt increase the chance of pregnancy?

Answer 1

No, according to https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4149942/ "Single and double donor sperm intrauterine insemination cycles: Does double IUI increase clinical pregnancy rates?":

Single and double donor IUI cycles had similar clinical pregnancy rates. This large data set did not demonstrate a benefit to routine double IUI in donor sperm cycles.

Their introduction gives an interesting overview of the previous literature on that matter:

Few studies have evaluated double IUI with donor sperm. These studies have been limited by small sample sizes and provide conflicting results. The first study to evaluate a double IUI regimen was performed by Khalifa et al. and demonstrated no benefit to double IUI (12). In contrast, Matilsky et al. demonstrated higher pregnancy rates using double IUI with frozen thawed donor sperm. The double IUI clinical pregnancy rate was 17.9% per cycle versus 5% per cycle with single IUI (13). More recently, Chavkin et al. conducted a retrospective study of 333 donor insemination cycles. Pregnancy rates over 3 cycles were 10.2% for single IUI compared to 13.7% for double IUI (p=0.47) (14). While the results were not statistically significant, the authors concluded that there may be a benefit to a second insemination.