Influence of embryo culture medium (G5 and HTF) on pregnancy and perinatal outcome after IVF: a multicenter RCT.

Study Question: Does embryo culture medium influence pregnancy and perinatal outcome in IVF?

Summary Answer: Embryo culture media used in IVF affect treatment efficacy and the birthweight of newborns.

What Is Known Already: A wide variety of culture media for human preimplantation embryos in IVF/ICSI treatments currently exists. It is unknown which medium is best in terms of clinical outcomes. Furthermore, it has been suggested that the culture medium used for the in vitro culture of embryos affects birthweight, but this has never been demonstrated by large randomized trials.

Study Design, Size, Duration: We conducted a multicenter, double-blind RCT comparing the use of HTF and G5 embryo culture media in IVF. Between July 2010 and May 2012, 836 couples (419 in the HTF group and 417 in the G5 group) were included. The allocated medium (1:1 allocation) was used in all treatment cycles a couple received within 1 year after randomization, including possible transfers with frozen-thawed embryos. The primary outcome was live birth rate.

Participants/materials, Setting, Methods: Couples that were scheduled for an IVF or an ICSI treatment at one of the six participating centers in the Netherlands or their affiliated clinics.

Main Results And The Role Of Chance: The live birth rate was higher, albeit nonsignificantly, in couples assigned to G5 than in couples assigned to HTF (44.1% (184/417) versus 37.9% (159/419); RR: 1.2; 95% confidence interval (CI): 0.99-1.37; P = 0.08). Number of utilizable embryos per cycle (2.8 ± 2.3 versus 2.3 ± 1.8; P < 0.001), implantation rate after fresh embryo transfer (20.2 versus 15.3%; P < 0.001) and clinical pregnancy rate (47.7 versus 40.1%; RR: 1.2; 95% CI: 1.02-1.39; P = 0.03) were significantly higher for couples assigned to G5 compared with those assigned to HTF. Of the 383 live born children in this trial, birthweight data from 380 children (300 singletons (G5: 163, HTF: 137) and 80 twin children (G5: 38, HTF: 42)) were retrieved. Birthweight was significantly lower in the G5 group compared with the HTF group, with a mean difference of 158 g (95% CI: 42-275 g; P = 0.008). More singletons were born preterm in the G5 group (8.6% (14/163) versus 2.2% (3/137), but singleton birthweight adjusted for gestational age and gender (z-score) was also lower in the G5 than in the HTF group (-0.13 ± 0.08 versus 0.17 ± 0.08; P = 0.008).

Limitations, Reasons For Caution: This study was powered to detect a 10% difference in live births while a smaller difference could still be clinically relevant. The effect of other culture media on perinatal outcome remains to be determined.

Wider Implications Of The Findings: Embryo culture media used in IVF affect not only treatment efficacy but also perinatal outcome. This suggests that the millions of human embryos that are cultured in vitro each year are sensitive to their environment. These findings should lead to increased awareness, mechanistic studies and legislative adaptations to protect IVF offspring during the first few days of their existence.

Study Funding/competing Interests: This project was partly funded by The NutsOhra foundation (Grant 1203-061) and March of Dimes (Grant 6-FY13-153). The authors declare no conflict of interest.

Trial Registration Number: NTR1979 (Netherlands Trial Registry).

Trial Registration Date: 1 September 2009.

Date Of First Patient's Enrolment: 18 July 2010.