To investigate the effect of smooth endoplasmic reticulum clusters (SERC) in human oocytes on the embryo development and pregnancy outcomes during intracytoplasmic sperm injection (ICSI) cycles and discuss the reason for it and the value of SERC-positive [SERC(+)] embryos.

Seven hundred and sixty-eight ICSI cycles during January 2014 to December 2015 were retrospectively analyzed and were divided into two groups: 681 cycles in which no SERC occurred in any M_II oocyte as group A, while 87 cycles in which at least one M_II oocyte was found with SERC in each cycle as group B. The concentrations of estradiol (E₂), progesterone (P) and luteinizing hormone (LH) as well as thickness of endometrium were measured on hCG injection day. Comparisons were made on the patients' age, disease course, the concentrations of basal hormones, dosage of Gn used, duration of stimulation, the number of oocytes retrieved, fertilization rates, good-quality embryo rates, available blastocyst rates, the occurrence of polycystic ovary syndrome (PCOS) patients, occurrence rate of moderate and severe ovarian hyperstimulation sydrome(OHSS), clinical pregnancy rate per cycle, implantation rate, miscarriage rate, live-birth rate and malformation rate. Group B was further divided into three subgroups: group SERC(+) (n=7) with all SERC(+) oocytes, group SERC(+/-) (n=14) consisting of one SERC(+) oocyte and one SERC(-) oocyte, group SERC(-) (n=25) with all SERC(-) oocytes. The comparison of fertilization rates, good-quality embryo rate and available blastocyst rate were made among these three subgroups.

The concentration of E₂ in group B [(2 976.6±1 246.3) ng/L] was significantly higher than that in group A [(2 323.4±871.4) ng/L] (P<0.05), while no significant differences were found on endometrium thickness as well as the concentrations of P and LH (P>0.05). Additionally, there were significantly lower fertilization rates (65.9%), good-quality embryo rate (28.6%) and available blastocyst rates (44.2%) (P<0.05), a significantly higher dosage of Gn used [(2 643.6±1 087.5) IU] (P<0.05) in group B than those in group A (74.9%, 33.4% and 50.4%) [(2 256.6±976.4) IU], while no significant difference on the age, disease course, duration of stimulation, the number of oocytes retrieved, the occurrence of PCOS patients, occurrence rate of moderate and severe OHSS, clinical pregnancy rate per cycle, implantation rate, miscarriage rate, live-birth rate and malformation rate (P>0.05) were found. Furthermore, within group B, the fertilization rate (59.6%) and available blastocyst rate (35.7%) from SERC(+) oocytes was significantly lower than that from SERC(-) oocytes (68.6%, 48.1%) (P<0.01).

During ICSI cycles, SERC in human oocytes adversely influence the early embryo development, but can develop into a healthy baby.

Oocyte; Smooth endoplasmic reticulum; Intracytoplasmic sperm injection (ICSI)