Reproductive Medicine Associates of New Jersey’s (RMANJ) Dr. Jason Franasiak, who leads RMANJ’s Marlton fertility center, recently published a study showing that embryos that develop slowly would benefit from Frozen Embryo Transfer (FET).
The study, published in the fertility journal Human Reproduction Open, showed that embryos that take a little more time to reach the blastulation stage have poorer sustained implantation rates than embryos that develop at the normal rate when transferred via Fresh Embryo Transfer.
But when those slowly-blastulating embryos were transferred via FET, their implantation rates were equivalent to their normally-blastulating counterparts – likely because they benefited from endometrial synchrony.
“When normal and slow blastulating embryos were frozen, they had identical outcomes,” Dr. Franasiak said. “This suggests that a lack of synchrony between a slowly-developing embryo and a woman’s endometrial lining may be a big factor in poor outcomes for slowly-blastulating embryos in fresh cycles.”
“By using Frozen Embryo Transfer, we can better sync up slowly-blastulating embryos with receptivity in the uterus, leading to better outcomes.”
Blastulation, an important early development stage for an embryo, during which it develops a fluid-filled cavity called the blastocoel, usually occurs on day 5 or 6 of embryo growth. In fresh cycles, the embryo is transferred to the uterus when it reaches the blastocyst stage. In frozen cycles, the embryo is frozen at the blastocyst stage, and transferred to the uterus later, at a point when the uterus is potentially more receptive.
It may sound hard to believe, but the uterus is highly-receptive to implantation by an embryo for approximately 24 hours during each ovulation cycle, meaning that the embryo has to be inserted at just the right time to have a chance to implant.
Due to premature elevation in progesterone levels, or to prevent Ovarian Hyperstimulation Syndrome (OHSS) – as well as to give geneticists time to perform genetic testing on the embryo – it became necessary to cryopreserve, or flash freeze, embryos until the time was right to use them. This process became known as FET, which RMANJ’s research showed led to higher implantation rates than fresh embryo transfer.
Now, Dr. Franasiak’s study has shed even more light on FET and its benefits for slowly-blastulating embryos.
Dr. Franasiak’s retrospective study, carried out using patient data from 2009 to 2013, analyzed three embryo groups: day 5 fresh embryo transfers, day 6 fresh embryo transfers and FETs. All three groups included two types of embryos: slowly-blastulating and normally-blastulating. The three groups comprised 3,391 embryos transferred to 1,966 patients.
The results showed that slowly-blastulating embryos had lower sustained implantation rates than normally-blastulating embryos in both day 5 and day 6 fresh transfers. For day 5, the sustained implantation rates were 44% vs. 64% in women under 35 years old and 18% vs. 56% in women 35 years old or older. For day 6, the sustained implantation rates were 52% vs. 63% in women under 35 years old and 32% vs. 48% in women 35 years old or older. Slowly-blastulating embryos transferred via FET, however, had the same sustained implantation rates as normally-blastulating embryos transferred via FET: 57% vs. 60% for women under 35 years old and 37% vs. 42% for women 35 years or older.
“These results will help us better understand and improve the overall success of IVF,” Dr. Franasiak said, “and help more patients achieve their dreams of parenthood.”
RMANJ is a worldwide leader in fertility science, committed to advancing the field one healthy baby at a time. To view our current research projects, click here. To make an appointment with a fertility doctor, click here or call 973.656.2089.