Long Cut Straw Provides Stable the Rates of Survival, Pregnancy and Live Birth for Vitrification of Human Blasotcysts

Abstract

Most of the commercial devices for vitrification are directly immersed into the warming solution (WS) for increasing of warming rate. However, the previous modified cut standard straw (MCS) which has reported is difficult to immerse into the WS. The aim of this study was to investigate whether the long cut straw (LCS) could be useful as a stable tool for vitrified-warmed human blastocysts. A total of 138 vitrified-warmed cycles were performed between November 2013 and November 2014 (exclusion criteria: women ≥38 years old, poor responder, surgical retrieval sperm, and severe male factor). The artificial shrinkage was conducted using 29-gauge needles. Ethylene glycol and dimethyl sulfoxide (7.5% and 15% (v/v)) were used as cryoprotectants. Freezing and warming were conducted using the LCS tool. The cap of LCS was removed using the forceps in the liquid nitrogen (LN₂) and then directly immersed into the first WS for 1 min at 37℃ (1 M sucrose). Only re-expanded blastocysts were transferred after it was cultured in sequential media for 18-20 h. A total of 294 blastocysts were warmed, and all were recovered (100%). Two hundred eighty-five embryos were survived (96.9%). The vitrifiedwarmed blastocysts of all patients were transferred without any cancellation. We were able to achieve a reasonable implantation (24.2%), following by clinical pregnancy (36.2%), which then continued to ongoing pregnancy (36.2%), and live birth (31.2%). Using LCS is achieved the acceptable rates of survival, pregnancy and live birth. Therefore, the LCS could be considered as a stable and simple tool for human embryo vitrificaton.

Keywords: Clinical outcomes; Human blastocysts; Long cut straw; Survival; Vitrification.

Fig. 1. Vitrification-warming of blastocysts using the long cut straw (LCS) and structure.

(A) Shape of the cap and cutting part. (B) Shape of the LCS. (C) Loading method. (D) Loaded blastocysts on the cutting part of the LCS with a minimum volume (×40). Red allow: Blastocyst.

Fig. 2. Vitrification-warming of embryos using the modified cut standard straw (MCS) and structure.

(A) Shape of the MCS. (B) Warming of embryos in the MCS by holding the MCS with bare hands. (C) Loaded embryos on the tip of the MCS with a minimum volume of vitrification solution (×40). (Lim et al., 2013).

Fig. 3. Comparison of the modified cut standard straw (MCS) and the Long Cut Straw (LCS) after warming.

Schematic structure of the MCS (A) and the LCS (B). (C) Image of suction warmed-blastocysts after warming into the MCS as capillary action. (D) Image of warmed-blastocysts after warming using the LCS, (a) Embryos are loaded onto the straw.

Fig. 4. Schematic diagram of loading process using the Long Cut Straw (LCS).

(A) Load the blastocyst on the distal end of the LCS. (B) Aspirate the blastocyst around VS #2 (<0.1 μL) using pipette.