Clinical efficacy of hyaluronate-containing embryo transfer medium in IVF/ICSI treatment cycles: a cohort study

Abstract

Study question: Does the duration of embryo exposure to hyaluronic acid (HA) enriched medium improve the rate of live birth events (LBEs)?

Summary answer: The use of embryo transfer (ET) medium rich in HA improves LBE (a singleton or twin live birth) regardless of the duration of exposure evaluated in this study, but does not alter gestation or birthweight (BW).

What is known already: HA-enriched medium is routinely used for ET in ART to facilitate implantation, despite inconclusive evidence on safety and efficacy.

Study design size duration: A cohort study was performed evaluating clinical treatment outcomes before and after HA-enriched ET medium was introduced into routine clinical practice. In total, 3391 fresh ET procedures were performed using low HA and HA-rich medium in women undergoing publicly funded IVF/ICSI treatment cycles between May 2011 and April 2015 were included in this cohort study.

Participants/materials setting methods: A total of 1018 ET performed using low HA medium were compared with 1198, and 1175 ET following exposure to HA-rich medium for 2-4 h (long HA exposure) or for 10-30 min (short HA exposure), respectively. A multiple logistic regression analysis was used to compare clinical outcomes including BW, gestational age and sex ratios between groups, whilst adjusting for patient age, previous attempt, incubator type and the number of embryos transferred.

Main results and the role of chance: The use of HA-rich medium for ET was positively and significantly associated with improved clinical pregnancy rate and LBE, for both exposure durations: long HA (odds ratio (OR) = 1.21, 95% CI: 0.99-1.48), short HA (OR = 1.32, 95% CI: 1.02-1.72) and pooled OR = 1.26, 95% CI: 1.03-1.54, relative to the use of low HA medium. A comparative analysis of the risks of early pregnancy loss following long HA exposure (OR = 0.76, 95% CI: 0.54-1.06), short HA exposure (OR = 0.84, 95% CI: 0.54-1.30) and late miscarriage (OR = 0.88, 95% CI: 0.51-1.53) (OR = 1.41, 95% CI 0.72-2.77), were lower and not statistically significant. Similarly, ordinary regression analysis of the differences in BW at both HA exposures; pooled OR = -0.9 (-117.1 to 115.3), and adjusted BW between both HA cohorts; pooled OR = -13.8 (-106.1 to 78.6) did not show any differences. However, a difference in gestational age (pooled OR -0.3 (-3.4 to 2.9)) and sex ratio (pooled OR 1.43 (0.95-2.15)) were observed but these were not statistically significant relative to low HA medium.

Limitations reasons for caution: The strength of a randomized treatment allocation was not available in this evaluation study, therefore effects of unmeasured or unknown confounding variables cannot be ruled out.

Wider implications of the findings: The result of this large cohort study strengthens the case for using HA-rich medium routinely at transfer, while adding the important clinical information that duration of exposure may not be critical. The composition and effects of commercial IVF culture media on success rate and safety remains a major controversy despite increasing calls for transparency and evidence-based practice in ART. Nonetheless, the lack of differences in BW and gestational age observed in this study were reassuring. However, an appraisal of clinical outcomes and appropriate research investigations are required for the continuous evaluation of efficacy and safety of HA.

Study funding/competing interests: T.A. is funded by a Clinical Doctoral Research Fellowship (CDRF) grant (reference: ICA-CDRF-2015-01-068) from the National Institute for Health Research (NIHR). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health. The authors declare no conflict of interest.

Keywords: birthweight; clinical pregnancy; embryo culture media; embryo transfer; hyaluronate-containing medium; live birth event; safety.

© The Author(s) 2021. Published by Oxford University Press on behalf of European Society of Human Reproduction and Embryology.

Figures

Figure 1.

Study design with changes in clinical practice. The diagram shows patient allocation and corresponding changes in the type of incubator, O2 level and embryo transfer (ET) media. ‘Box + K-system’ refer to embryos that were initially cultured in the conventional style box incubator up to day 3 before transfer into K-systems incubator for blastocyst culture. HA, hyaluronic acid.

Figure 2.

A flow-chart illustrating the embryo culture system. Fertilization checks were performed on day 1 (D1) between 16 and 18 h after insemination by conventional IVF or ICSI. Normal fertilized (2PN) oocytes were allocated to either a K-system (G185) or Embryoscope incubator based on space availability. Pronuclear stage embryos were cultured in G1+ medium until day 3 (D3). In cases where only one or two embryos are available, ET was performed on day 2. Embryos cultured in the conventional style box incubator and K-system were graded morphologically under a stereomicroscope at, approximately, post-insemination/injection on day 2 (44 ± 1 h), D3 (68 ± 1 h), D5 (116 ± 2 h) and D6 (140 ± 1 h). In the Embryoscope, morphological grading of embryos was performed at the same time-points by examining the time-lapse images. On D3, embryos were selected for replacement, for cryopreservation or for extended culture to the blastocyst stage: the latter were transferred to new culture dishes or Embryoscope slides containing G2+ medium for further culture to day 6. On day 5, the highest quality blastocysts were selected for either single embryo transfer (SET) or double embryo transfer (DET). Cryopreservation was by slow freezing (SF) for cleavage on D3 and vitrification (VIT) for blastocyst stage embryos. TLI, time lapse incubator **Embryoscope incubator timelapse assessment, *stereomicroscope assessment.