To the Editor: Approximately 40% to 50% of all human conceptions are lost before 20 weeks of gestation.1 Recent animal studies suggest that the endocannabinoid anandamide (N-arachidonoyl-ethanolamine) is critical for both the synchronous development of the blastocyst and the endometrium in preparation for implantation, with low anandamide levels essential for successful implantation.2 Plasma anandamide levels are regulated by fatty acid amide hydrolase (FAAH),
the enzyme (up-regulated by progesterone) that metabolizes anandamide into arachidonic acid and ethanolamine.3 Increased FAAH expression and lower anandamide levels have been demonstrated at the implantation site and low FAAH expression and high anandamide levels at the interimplantation site prior to successful implantation.2 Levels of FAAH in peripheral blood mononuclear cells from uncomplicated early pregnancies were significantly lower in women who subsequently miscarried.4 In women undergoing in vitro fertilization and embryo transfer, high plasma anandamide level at 6 weeks after embryo transfer was associated with failure to achieve an ongoing pregnancy.5 We therefore investigated whether plasma anandamide levels could predict outcome in women presenting with threatened miscarriage.
Plasma Anandamide Concentration and Pregnancy Outcome in Women With Threatened Miscarriage. JAMA. 2008;299(10):1135–1136. doi:10.1001/jama.299.10.1135
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