The comparison between short-term fertilization and conventional fertilization in in vitro fertilization treatment: a propensity score matching study

Short-term IVF (S-IVF) is a fertilization approach to co-incubate the sperm and oocyte for a short duration and denude the cumulus cells afterwards. The S-IVF combined with early rescue intracytoplasmic sperm injection (ICSI) strategy can reduce the occurrence of both total fertilization failure (TFF) and the lower fertilization rate (<30%). However, there is still no consensus regarding the use of S-IVF. This study aimed to compare short-term in vitro fertilization (S-IVF) with conventional in vitro fertilization (C-IVF) in terms of fertilization, embryo developmental potential, and clinical outcomes. We used propensity score matching (PSM) to construct a 1:5 cohort of S-IVF and C-IVF cycles and compared fertilization, embryo developmental potential, and clinical outcomes between the two groups. We screened 68 S-IVF and 340 C-IVF patients (each in their first ART cycle—so cycle and patient numbers are identical) by baseline characteristics. The primary outcome was the fertilization rate, and the secondary outcomes were the pregnancy rate and abortion rate in cohort. The results showed that the C-IVF group had a higher fertilization rate [84% vs. 78%, p < 0.05], two-pronucleus (2PN) rate [67% vs. 60%, p < 0.05], and one-pronucleus (1PN) rate [5% vs. 3%, p < 0.05] compared with the S-IVF group. Furthermore, in the C-IVF group, the zero-pronucleus (0PN) rate was lower than in the S-IVF group (11% vs. 20%, mean difference -9 percentage points, 95% CI -12.5 to -5.5, p < 0.001). The good-quality blastocyst rate was numerically higher in the C-IVF group than in the S-IVF group, but the difference was not statistically significant. There was no significant difference in pregnancy rate or abortion rate in cohort between the two groups (early abortion rate among clinical pregnancies: 15.1% [14/93] in C-IVF versus 13.0% [3/23] in S-IVF, p = 1.000). In conclusion, C-IVF had a higher fertilization rate, 2PN rate, and 1PN rate but a lower 0PN rate compared with S-IVF, while there was no difference in embryo development and clinical outcomes.