Soluble HLA-G is an independent factor for the prediction of pregnancy outcome after ART: a German multi-centre study

Soluble HLA-G (sHLA-G) has been suggested as a non-invasive marker for embryo selection to improve pregnancy rates after assisted reproduction technique (ART). Our study aimed at the identification of parameters influencing the detection of sHLA-G in embryo cultures (ECs) and at the prognostic relevance of sHLA-G in a multi-centre study.

In total 4212 EC from 2364 cycles were randomly collected from 29 German ART centres and analysed for sHLA-G by Luminex-based technology.

Among test and culture conditions, only the cleavage stage of the embryo was identified as an independent factor for sHLA-G detection (P < 0.001). Overall, sHLA-G was significantly associated with pregnancy after ART [P < 0.001; odds ratio: 2.0 (95% CI: 1.7-2.4)], suggesting that sHLA-G testing might improve the pregnancy rate from 30 to 40%. Importantly, the sHLA-G status of embryos could be associated with pregnancy after single embryo transfer [P = 0.002; odds ratio: 3.3 (95% CI: 1.5-6.8)] doubling the probability of pregnancy rate to 26% after sHLA-G testing. The patient's age, number of transferred embryos, morphological grading [EXP(B): 4.3 (95% CI: 2.1-8.9)] of embryos and sHLA-G status [EXP(B): 2.3 (95% CI: 1.8-3.1)] were independent predictors of pregnancy, with the latter two being most powerful.

This study provides significant evidence that the morphological scoring system is still the best strategy for the selection of embryos but that sHLA-G might be considered as a second parameter if a choice has to be made between embryos of morphologically equal quality.