Aim: To evaluate the impact of adding L-carnitine (LC) to usual endometrial preparation on endometrial receptivity in women with at least one prior implantation failure during intra-cytoplasmic sperm injection (ICSI)/ frozen embryo transfer (FET) cycles.
Methods: This prospective, double-blinded, placebo-controlled, randomized, parallel group, concealed allocation, superiority trial was conducted at a private specialized IVF center Benha, El-Qalubia, Egypt, between November 2015 and May 2017 .124 infertile couples with at least one prior implantation failure (PIF) in ICSI / FET cycles were allocated to receive usual endometrial preparation plus 3 gm LC /daily until transfer (62) or received placebo (62) plus usual estradiol valerate. Outcomes were endometrial thickness, implantation rate, chemical pregnancy rate, clinical pregnancy rate, ongoing implantation rate, ongoing pregnancy rate, live birth rate and live borne babies rate.
Results: infertile women with at least one prior implantation failure in ICSI/FET cycles co treated with L-Carnitine showed significantly thicker endometrium (mm) 9.8  1.2 in LC vs 8.4  0.7 in non LC with  (95% CI) = 1.4 (1.74, 1.05) and higher chemical pregnancy rate 46 (74.2%) in LC vs 22 (35.4%) in non LC with PP (95% CI) = 38.8 (71.46; 52.96) and RR (95% CI) = 2.09 (1.44, 30.1) and NNT (95% CI) = 3 (2, 5). Also, higher clinical pregnancy rate (34 (54.8%)) in LC vs 14 (22.6%) in non LC with PP (95% CI) = 32.2% (15.13, 46.77) and RR (95% CI) = 2.4 (1.45, 40.5) and NNT (95% CI) = 4 (3 – 7) as well as higher live birth rate, live bone rate of singletons fetus (P < 0.05).
Conclusion: The data showed in this trial support the supplementation of LC to usual endometrial preparation in women with at least one prior implantation failure in ICSI / FET cycles as it improved endometrial receptivity indicated by improved implantation rate, clinical pregnancy rate, live birth rate.