First clinical study comparing the G-Series™ culture media G-1™ and G-2™ with G-TL™

G-TLis a medium developed for undisturbed embryo culture in time-lapse systems. Below follows a summary of the first published clinical study comparing G-TL and the G-Series sequential media G-1 and G-2.

G-TL is designed for embryo culture in time-lapse systems and does not require medium change. The aim of this study was to investigate if G-TL supports embryo development equally well as the sequential embryo culture media. The study was designed as a prospective, randomised, double blinded trial and was performed in four independent clinics, two in Sweden and two in the United States.

Pronuclear stage sibling embryos were prospectively randomised to compare embryo development in the Primo Vision time-lapse system. Zygotes randomised to the G-1/G-2 group underwent medium change on day three while the embryos of the G-TL group were cultured continuously without medium change until day 5/6.

The primary endpoint was percentage good quality blastocysts (GQB) on day 5 per randomised patient. Secondary endpoints were percentage of good quality embryos on day 3, blastocyst utilisation rate and total blastocyst rate per 2PN embryo.

Embryos were morphologically assessed using the Alpha/ESHRE consensus scoring system on day 3 and day 5/6. A GQB was defined as 2:2:2 or better. The couple needed at least 6 normally fertilised embryos to be included in the study. A total of 1356 zygotes from 128 patients were used.

Ammonium build up is a concern in uninterrupted embryo culture. Therefore, ammonium concentration was measured in the culture medium with or without human embryos cultured at +37⁰ for 144 hours. Results for primary and secondary endpoints are displayed in Figure 1.

There was no difference between media systems for the primary endpoint. Regarding the secondary endpoints, a difference was seen in the rate of good quality embryos (GQE) on day 3. 


Figure 1. Embryo development data of primary and secondary end points. *p<0.0005 The difference on day 3 could also be seen by time-lapse.

Time-lapse analysis revealed that the embryos in the G-TL group needed an average of 1h30 longer to complete the third cleavage cycle. This difference was significant but later during embryo development it disappeared completely resulting in similar numbers of GQB on day 5 as well as utilisation rate. Results on embryo kinetics can be found in Figure 2.


Figure 2. Time-lapse profiles of sibling embryos cultured in the two different culture media systems.

The ammonium level was higher in G-1/G-2 before embryo culture or exposure to +37⁰C than in G-TL. This difference remained also after embryo culture but the ammonium levels were well below limits reported to have an impact on embryo development.

In conclusion, with the largest prospective randomised sibling embryo study to date that has compared a medium for undisturbed embryo culture and sequential media from the same manufacturer (Vitrolife) using time-lapse; the two media systems are equivalent in relation to blastocyst quality and rate.

REF: Hardarson T, et al: Fertil Steril. 2015 Dec;104(6):1452-9.e1-4. doi: 10.1016/j.fertnstert.2015.08.037. Epub 2015 Sep 25.