When is it the sperm’s fault? the incidence of low fertilization in matched donor egg cycles

The allocation of donor frozen oocytes may involve several couples, allowing for the same lot of donor oocytes to be inseminated by different sperm populations. Donor egg banks provide eggs from the same women's retrieval to different laboratories. This leads to the same egg lots being inseminated by different males. The objective of this study was to use data from this clinical scenario to identify the incidence of true paternally related poor fertilization. Donor egg cases from a single donor egg bank where 4 or more oocytes underwent ICSI were selected from a large university affiliated private clinic between April 2014 to August 2021. Cases with ≤ 40% fertilization rate were identified, and 26 cases were then matched to the same donor egg lot that was utilized with different sperm in other clinics to ascertain what the concordant egg fertilization rates were. The number of oocytes and fertilization rates from the one clinic with low fertilization rates were compared with the remaining clinics for each egg lot case. Paired t-tests were used to compare each single poor fertilization rate case with its same donor oocyte lot from other clinics. Overall 200 cases were identified from one donor egg bank for analysis. Of those 200 cases 43 (21.5%) had a ≤ 40% fertilization rate and 20 (10.0%) had a ≤ 30% fertilization rate. In 26 matched cases from the same egg lot all concordant cases had high fertilization rates. The mean (± SD) of egg number and fertilization rates for Donors from the one clinic and matched egg lots are shown in Table 1. The overall fertilization rate from the low fertilization patients compared to their egg lot counterparts using other sperm were significantly different. In donor egg cases, at least 26 cases experienced a low fertilization rate, which was confirmed to be sperm related when matched with cases using the same donor egg lot but a different sperm source. This indicates that more emphasis on male factor infertility is needed in the field instead of the reflex to always attribute infertility to an egg problem.