Grants include NIH 5T32HD040135-12 (J.S.R.), R01 HD065435 (K.H.M.), NIH T32 HD049305 (J.L.S.) and ACOG Research Grant (M.B.S.). The authors report no conflicts of interest.

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Purpose Implantation failure is a major limiting factor of successful in vitro fertilization (IVF). The objective of this study was to determine if endometrial mechanical stimulation (EMS) by endometrial biopsy in the luteal phase of the cycle prior to embryo transfer (ET) improves clinical outcomes in an unselected subfertile population. Methods Double-blind, randomized controlled trial of EMS versus sham biopsy and odds of clinical pregnancy after IVF and embryo transfer. Secondary outcomes included spontaneous miscarriage and live birth. Results One hundred women enrolled and were randomized from 2013 to 2017. Enrollment was terminated after futility analysis showed no difference in clinical pregnancy between EMS versus control, 47.2% vs 61.7% (OR 0.55, 95% CI 0.25-1.23, p = 0.15). There were no significant differences between women who underwent EMS and those who did not in terms of positive pregnancy test 54.7% vs 63.8% (OR 0.69, 95% CI 0.31-1.53, p = 0.36), miscarriage 7.5% vs 2.1% (OR 3.76 95% CI 0.41-34.85, p = 0.22), or live birth 43.4% vs 61.7% (OR 0.48 95% CI 0.21-1.06, p = 0.07). Conclusions EMS in the luteal phase of the cycle preceding embryo transfer does not improve clinical outcomes in an unselected subfertile population and may result in a lower live birth rate. We caution the routine use of EMS in an unselected population.

Successful embryonic implantation is the result of a receptive endometrium, a functional embryo at the blastocyst stage and a synchronized dialog between maternal and embryonic tissues. Successful implantation requires the endometrium to undergo steroid-dependent change during each menstrual cycle, exhibiting a short period of embryonic receptivity known as the window of implantation. The term ''endometrial receptivity'' was introduced to define the state of the endometrium during the window of implantation. It refers to the ability of the endometrium to undergo changes that will allow the blastocyst to attach, penetrate, and induce localized changes in the endometrial stroma. These changes are metabolically demanding, and glucose metabolism has been proven to be important for the preparation of the endometrium for embryo implantation. Obesity and polycystic ovary syndrome (PCOS) represent 2 common metabolic disorders that are associated with subfertility. The aim of this review is to summarize the effect of obesity and PCOS on endometrial receptivity at the time of implantation. Focus will be on metabolic alterations that regulate decidualization, including glucose metabolism, hyperinsulinemia, and hyperandrogenism.

Embryo implantation and development requires the endometrial stromal cells (ESCs) to undergo decidualization. This differentiation process requires glucose utilization, and blockade of the pentose phosphate pathway inhibits decidualization of ESCs both in vitro and in vivo. Glucose and fatty acids are energy substrates for many cell types, and fatty acid beta-oxidation is critical for embryo implantation. Here, we investigated whether beta-oxidation is required for decidualization of ESCs. As assessed by marker gene expression, decidualization of human primary ESCs was blocked by reducing activity of carnitine calmitoyltransferase I, the rate-limiting enzyme in beta-oxidation, either by short hairpin RNA-mediated silencing or by treatment with the inhibitor etomoxir. Ranolazine (RAN), a partial beta-oxidation inhibitor, blocked early decidualization of a human ESC line. However, decidualization resumed after several days, most likely due to a compensatory up-regulation of GLUT1 expression and an increase in glucose metabolism. Simultaneous inhibition of the beta-oxidation pathway with RAN and the pentose phosphate pathway with glucosamine (GlcN) impaired in vitro decidualization of human ESCs more strongly than inhibition of either pathway alone. These findings were confirmed in murine ESCs in vitro, and exposure to RAN plus GlcN inhibited decidualization in vivo in a deciduoma model. Finally, intrauterine implantation of time-release RAN and GlcN pellets reduced pup number. Importantly, pup number returned to normal after the end of the pellet-active period. This work indicates that both fatty acids and glucose metabolism pathways are important for ESC decidualization, and suggests novel pathways to target for the design of future nonhormonal contraceptives.