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Frozen Embryos Beat Fresh Ones for IVF

Women undergoing IVF who have had embryos fail to implant are almost twice as successful using frozen ones than fresh ones, according to a study published in The Australian and New Zealand Journal of Obstetrics and Gynaecology (

The study followed 84 patients who underwent 140 IVF cycles to identify success rates by comparing the two different types of transfers (frozen versus fresh) with recurring unsuccessful cycles. “We found the birth rate for frozen and thawed embryos was 39%, compared to 20% for fresh embryos,” said Prof Roger Hart of the University of Western Australia’s Division of Obstetrics and Gynaecology.

The study excluded any correctable factors present within the woman that may have limited the embryo implanting, and then undertook preimplantation genetic screening of embryos on the third day to ensure there were no abnormalities. “We examined the chromosomal status of the embryo, as unfortunately the most common reason an embryo does not implant is because it is chromosomally abnormal,” Hart said.

“The study results demonstrate that a frozen embryo implantation is more successful than transferring the embryo straight after the biopsy in a fresh IVF cycle, as the environment within the uterus is more ‘normal’ in a subsequent natural cycle than during an IVF cycle where the hormone levels are often very high.”

Hart said there were also other factors that impacted the success of the cycle. “The success of the transfer was much less if the woman was significantly overweight, if there were a lower number of cells present within the embryo at the time of biopsy, and if the pregnancy hormone level was lower at the time of the pregnancy test,” he said. “Women under the age of 35 also have higher success rates.”

The study also showed that biopsing an embryo after 3 days could impair growth, which suggested that the more advanced an embryo was at the time of biopsy, the more it would withstand the biopsy process. “One of the things to draw from this study is that some women should opt for a frozen embryo transfer over a fresh IVF cycle, which may help improve the implantation potential of the embryo,” Hart said.