Purpose: In assisted reproductive technology, normal zygotes are bipronuclear (2PN) during fertilization confirmation; however, sometimes, nonpronuclear zygotes (0PN) and monopronuclear zygotes (1PN) are found during routine observations.
Methods: To elucidate the clinical usefulness of in vitro-fertilized embryos, we investigated the rates of clinical pregnancy, live birth, miscarriage, and congenital abnormality after transfer of frozen-thawed 1PN- and 0PN-derived single blastocysts at Denentoshi Ladies Clinic, Kanagawa, Japan.
Results: The rates of pregnancy and live birth for 1PN-derived blastocysts obtained by conventional in vitro fertilization were 37.5% and 27.1%, respectively, which was not significantly different from those for 2PN-derived blastocysts; however, the rates for 0PN-derived blastocysts were significantly lower. The pregnancy and live birth rates for 0PN-derived embryos obtained by intracytoplasmic sperm injection (ICSI) were 45.7% and 34.8%, respectively, which was not significantly different from those for 2PN-derived blastocysts; however, the rates for 1PN-derived blastocysts were significantly lower (4.0% for both) than those for 2PN- and 0PN-derived blastocysts. No congenital abnormalities were found in infants resulting from transfer of 0PN- or 1PN-derived blastocysts.
Conclusions: Both 1PN- and 0PN-derived blastocysts can be used for embryo transfer; however, care should be taken in making decisions about 1PN-derived blastocysts, especially if they are obtained by ICSI.
Keywords: abnormal fertilization; clinical outcomes; frozen‐thawed blastocyst transfer; monopronuclear zygotes; nonpronuclear zygotes.