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Zeinab Kazemianpour: That Heart-Stopping Moment During Embryo Warming

Zeinab Kazemianpour/LinkedIn

Nov 9, 2026, 16:48

Zeinab Kazemianpour: That Heart-Stopping Moment During Embryo Warming

Zeinab Kazemianpour, Clinical Embryologist at Nikan Hospital, shared on LinkedIn:

“That heart-stopping moment during embryo warming: When bubbles make your embryo disappear!

Every clinical embryologist knows this moment.

You transfer the Cryotop from liquid nitrogen (LN₂) into the pre-warmed thawing solution (TS/T1) at 37°C.

Instead of watching the embryo gently detach from the Cryotop, bubbles suddenly appear, the liquid starts moving, and your embryo disappears from the field of view.

Now comes the stressful part: searching the center-well dish while the 1-minute timer is ticking!

But what causes this sudden bubbling?

Several factors may contribute:

Residual liquid nitrogen: Small amounts of LN₂ remaining on the Cryotop may rapidly vaporize upon contact with the warming solution, potentially contributing to bubble formation and local fluid movement.
Temperature and solution gradients: Differences between the vitrification solution (VS), containing DMSO, ethylene glycol, and sucrose, and the warming solution (TS), containing sucrose, together with the sudden temperature change, may contribute to fluid movement during immersion.
Air bubbles: Small air bubbles associated with Cryotop handling or immersion may also affect visibility during warming.

How can we minimize the risk of losing the embryo from view?

Follow the manufacturer’s instructions for Cryotop immersion and handling.
Prepare your stereomicroscope and focus on the dish before starting the warming procedure.
Observe the Cryotop carefully during immersion and avoid unnecessary movements.
If the embryo disappears from view, carefully inspect the Cryotop and surrounding dish before proceeding.

The most stressful part isn’t always the warming itself – it’s that moment when you can’t see your embryo.

Every laboratory develops its own practical techniques through experience.

What is your go-to technique for minimizing bubbles and keeping the embryo in view during T1 warming?

Let’s share our laboratory experiences in the comments!”

Zeinab Kazemianpour: That Heart-Stopping Moment During Embryo Warming