Could blastocysts derived from abnormal fertilized zygotes be used? A systematic review and meta-analysis

Current guidelines advise against using embryos derived from mono-pronuclei (1PN) or non-pronuclei (0PN) zygotes for clinical purposes. Nevertheless, recent studies have demonstrated that 1PN and 0PN zygotes can lead to healthy births. This study aimed to investigate the pregnancy outcomes of 1PN and 0PN blastocysts.

PubMed, EMBASE, Web of Science and Cochrane databases were searched up to 14 March 2024. Eligible studies enrolled participants transferring 0PN or 1PN blastocysts, with two pronuclei (2PN) blastocysts used as the control. Clinical pregnancy rate, miscarriage rate and live birth rate were the main outcomes. The results were presented as odds ratios (OR) with 95 % confidence intervals (CI) using random-effect models with the Mantel-Haenszel method. Additionally, a stratified analysis was conducted based on the type of fertilization. The Newcastle-Ottawa scale (NOS) was used to evaluate the quality of the included studies.

In total, 270 articles were identified, with 16 ultimately included in the meta-analysis. In total, 57,835 cycles were analysed: 1071 cycles in the 1PN group, 2324 cycles in the 0PN group, and 54,440 cycles in the 2PN group. The results indicated that 1PN or 0PN blastocysts were associated with lower clinical pregnancy rates and live birth rates than 2PN blastocysts. Interestingly, there was no significant difference in live birth rate between 1PN blastocysts and 2PN blastocysts in patients undergoing intracytoplasmic sperm injection (ICSI), nor between 0PN blastocysts and 2PN blastocysts in patients undergoing in-vitro fertilization (IVF).

Careful consideration should be given to the utilization of 1PN and 0PN blastocysts, especially if an improved methodology of non-invasive assessment of fertilization is available. At the very least, 1PN blastocysts in patients undergoing IVF and 0PN blastocysts in patients undergoing ICSI represent viable fertility options for patients facing abnormal fertilization in clinical practice.