Senior Embryologist at Pacific Fertility Center to Present Paper at the Pacific Coast Reproductive Society’s Annual Meeting in March 2015

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Confirming earlier mouse model observations, the paper details for the first time how hardening of the human ovum’s membrane after vitrification may affect embryo hatching and clinical pregnancy rates.

The Pacific Coast Reproductive Society has accepted a Pacific Fertility Center (PFC) paper for oral presentation at its 63rd Annual Meeting, which runs from March 11-15, 2015, in Rancho Mirage, CA. The paper is entitled “Timing of Blastocyst Hatching after Vitrification and Warming: Impact on Clinical Pregnancy Rate.” Out of 100 submissions, it is one of eight selected for oral presentation.

A strong membrane (zona pellucida-ZP) forms around the ovum during development in the ovary. Previous evidence suggested that freezing (vitrification) alters the properties of this membrane, possibly warranting its removal prior to frozen embryo transfer (FET) in certain cases.

“We conducted this study to characterize the response of the zona pellucida to blastocyst expansion after warming and to develop an algorithm to predict implantation potential,” said Sergio Vaccari, PhD, lead author and senior embryologist at PFC. The blastocyst is a thin-walled hollow structure in early embryonic development.

Finding that the elasticity of the ZP was significantly reduced after vitrification, the researchers photographed blastocysts immediately after warming, as well as one and two hours later. To develop an algorithm for viability, they compared the blastocysts’ volume changes to transfer outcomes. It is common practice in ART clinics to make one small hole in the ZP, immediately prior to a frozen embryo transfer. Embryos with small holes had trouble hatching and were trapped inside for 6–48 hours or failed to escape altogether, despite re-expansion that appeared normal.

However, embryos that expanded in volume by at least 20 percent in the first hour and/or 50 percent within two hours produced a significantly higher clinical pregnancy rate. Making a large opening in the ZP allowed embryos to hatch completely within four hours.

Based on this work, the researchers suggest that some frozen embryos may benefit from ZP removal after warming and before transfer, especially given that some embryos were observed trapped inside the ZP despite exhibiting good rates of re-expansion.

About Pacific Fertility Center
Pacific Fertility Center is an international destination for male and female fertility treatment and care. It provides an extensive array of fertility treatment options ranging from intrauterine insemination (IUI), intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF) to cutting-edge technology such as vitrification and genetic testing of embryos. For more information: http://www.pacificfertilitycenter.com.

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Media Contact
Renee H. Scudder, MS
415-249-3662
scudder(at)pacificfertility(dot)com

Pacific Fertility Center
55 Francisco Street, Fifth Floor
San Francisco, CA 94133

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