Embryo freezing and thawing

CARE embryologists have been freezing and thawing embryos for over 20 years, our latest look at thaw cycles this year has shown some great results. 2720 embryos were thawed in 2018 ... and 97% thawed successfully, CAREs best year! The outcomes from these also look good, with a 41% clinical pregnancy rate for all patient ages. Fantastic!


So how do we do it?

Our embryos are frozen on special straws which are stored in vessels containing liquid nitrogen. This keeps embryos at extremely low temperatures of -196 C. This low temperature ensures there is no biological activity meaning the embryos can be stored for many years without deteriorating.

The embryologist pipettes the embryo onto the tip of a special straw before it is plunged into liquid nitrogen. The embryos are only a tenth of a millimetre in size, so we use a microscope and a steady hand to help us. At CARE we use a freeze method called vitrificationwhich we believe has helped to improve our freeze/thaw success over recent years.



To thaw an embryo, the process is essentially reversed. The straw tip is plunged from the liquid nitrogen into a warmed solution. The embryo floats off the tip and is moved into different solutions until it has recovered, sometimes ‘expanded’, before it is returned to an incubator. The embryo can be transferred to a patient the same day.



In this video George, an embryologist in Nottingham, is thawing an embryo. He is moving the embryo between solutions using a very fine pipette. It takes about 20 minutes, but I have made some edits! 



At CARE we have 1000's of embryos stored for patients and we understand just how precious they are. Our frozen embryos are kept in dedicated secure areas and each straw labelled with a unique bar code as well as names, date of birth etc. All vessels are fitted with 24-hour alarms and are checked regularly by trained embryologists. So safer than safe!


Did you know frozen embryos can be moved between clinics? CARE has safely received 100s of frozen embryos from all over the UK and the World. CARE can assist in the process of moving frozen embryos, sperm or eggs to its clinics. We work with a number of specialist couriers to make it an easy and safe procedure. Our embryologists liaise with other clinics to ensure all the original screening, consent and freezing records are passed on.

Please contact CARE to find out more if this is something you are interested in.

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