Healthy Monozygotic Twins Born from a Vitrified Blastocyst Derived from a Vitrified Oocyte, and a Highly Efficient Vitrification for Freezing Human Oocytes and Blastsocysts

We used simplified oocyte/embryo vitrification and warming protocols (Irvine Scientific) combined with vitristraws (SciTech Invention) to freeze and thaw human oocytes and blastsocysts. Throughout the year of 2014, twelve recipients were transferred embryos developed from vitrified donor oocytes, and fourteen recipients were transferred embryos developed from fresh donor oocytes at the North Carolina center for reproductive medicine (NCCRM). There were no statistically significant differences in donor age (25.9 ± 3.6 vs 24.9 ± 3.2) and recipient age (43.0 ± 5.4 vs 41.4 ± 6.8), fertilization rates (86.2% vs 87.0%), blastocyst development rates (50.0% vs 53.8%), number of embryo transferred (1.7 ± 0.8 vs 1.9 ± 0.4), clinical pregnancy rates per transfer (75.0% vs 71.4%) and live birth rates per transfer (66.7% vs 57.1%) between vitrified and fresh oocyte cycles, respectively. The results demonstrate that vitrification techniques can be used to cryopreserve human oocytes for future use. We are also reporting the live birth of healthy monozygotic twins resulted from a re-vitrified blastocyst derived from a vitrified oocyte. Oocytes from a 30-year-old donor were vitrified in vitristraws. Seven out of eight oocytes survived after thawing on November 16, 2013. Those seven oocytes were inseminated by intracytoplasmic sperm injection (ICSI) at about 2 hours post thawing. All seven oocytes were tested as fertilized by pronuclear check at 18 hours after ICSI. Those fertilized oocytes showed normal cleavage on day 2 and day 3. Four of them developed to blastsocysts by culturing in continuous single culture medium in a tri-gas incubator for 5 days. Two blastsocysts were transferred to a 43-year-old recipient, but that did not result in a pregnancy. The other two blastsocysts were re-vitrified in a vitristraw. The re-vitrified blastsocysts were thawed and then transferred to the same recipient on May 8, 2014. The patient achieved a normal pregnancy on her second transfer. On June 14, 2014, an ultrasound scan detected two heartbeats in one gestational sac. Two healthy monozygotic boys (weighing 2466g and 2353g) were born on January 13, 2015. To our knowledge, this is the first report of monozygotic twins born from an embryo by twice vitrification at oocyte and blastocyst stage.