Researchers in a 2026 meta-analysis combined the results of 9 studies and found that embryos from 0PN zygotes had similar pregnancy outcomes to embryos from normally fertilized (2PN) zygotes, despite being less likely to develop into blastocysts.
Abnormal fertilization
Researchers in a 2026 study found that about 0.4% of blastocysts derived from apparently normal 2PN fertilization were triploid, and although these embryos were more likely to have abnormal polar body extrusion, genetic testing is still the only reliable way to identify them.
A 2025 case report shows that some ICSI-derived 3PN embryos can be rescued by removing the extra female pronucleus, resulting in a healthy live birth, but the technique remains experimental.
A 2025 study found that 0PN zygotes can actually be normally fertilized but missed during the standard 16–18 hour fertilization check, while those that never form pronuclei are likely unfertilized eggs, supporting a slightly earlier check around 16–17 hours and continued culture of 0PNs to the blastocyst stage for confirmation of fertilization.
A 2025 study of women with repeated IVF failure and unexplained infertility found that about 13% had mutations affecting egg or embryo development, mostly in the TUBB8 and PATL2 genes, suggesting that many “unexplained” cases may have underlying genetic causes.
A 2025 meta-analysis found that while 1PN zygotes don’t convert to blastocyst as well and have lower success rates when untested, those confirmed as euploid can lead to healthy births, but extra care is needed to confirm they are truly normal.
This post covers what occurs during normal fertilization and what it means to have an abnormally fertilized zygote (0PN, 1PN, 3PN, 4PN). Using PGT to test these embryos reveals that many have the correct number of chromosome sets and can lead to successful live births.