Deliveries of normal healthy babies from embryos originating from oocytes showing the presence of smooth endoplasmic reticulum aggregates

Abstract

Should oocytes showing the presence of smooth endoplasmic reticulum aggregates (SER) be considered for embryo transfer? The present study shows that embryos derived from metaphase II oocyte with visible SER (SER+MII) have the capacity to develop normally and may lead to newborns with no major malformations. It has been reported that the presence of SER in the cytoplasm of oocytes has a negative impact on embryo development, and is associated with a decreased clinical outcome and an increased risk of congenital anomalies. Therefore, it has been recommended that embryos derived from SER-positive oocytes should not be transferred. Consecutive ICSI cycles with at least one SER+MII oocyte were retrospectively analyzed regarding embryological and pregnancy outcome and compared with ICSI cycles showing only oocytes without SER (SER-MII). In total, 394 SER-positive (SER+) cycles and 6845 SER-negative (SER-) cycles were analyzed. The Student's t-test, one-way analysis of variance test and χ(2) test were used for statistical analysis. P value of <0.05 was considered statistically significant. Comparable fertilization rates were observed in SER+ (76.2%) and SER- (73.5%) cycles. In case of blastocyst culture, the cycle efficiency was lower in SER+ than in SER- cycles (mean 42.2 versus 62.8%, P < 0.001). The pregnancy and clinical pregnancy (CP) rates per embryo transfer (ET) were comparable for SER+ and SER- cycles (37.6 versus 37.8% and 33.0 versus 32.4%, respectively). In the SER+ cycles, the fertilization rates of SER+MII and SER-MII (72.9 versus 77.0%), as well as the capacity to develop into good-quality embryos on Days 3 (62.3 versus 63.7%) and 5 (45.4 versus 47.4%), were similar. In the 364 SER+ cycles, the ETs were subdivided in: ET with only SER+MII (n = 31; 8.5%), ET with only SER-MII (n = 235; 64.5%) and ET with mixed SER+ and SER-MII (n = 98; 26.9%). The pregnancy (25.8, 37.4 and 41.8%, respectively) and CP rates (22.6, 32.4 and 37.9%, respectively) were not different between the three subgroups. Among the cycles with known outcome, there was no difference in the rate of major malformations between SER+ cycles (5.3%) and SER- cycles (2.1%). Moreover, no major malformations were reported from the live borns definitely originating from SER+MII embryos. In addition, three newborns, from single ET with frozen-thawed embryos originating from SER+MII oocytes, were delivered and presented no major malformation. Taking into account the previous publications and our neonatal data, a follow-up of the children born after ET with embryos originating from SER+ cycles is encouraged. More studies should be performed to investigate the origin and effect of SER aggregates on the molecular status of oocytes and embryos. No external funding was either sought or obtained for this study and there are no potential competing interests. Not applicable.