When thinking about it a little more it didn't surprise me that reproductive organs would contain the ligand, since they are known to express the receptors:
"With respect to reproductive organs, cannabinoid receptors and/or endocannabinoids have been detected in the pituitary gland, testis, Leydig cells, epididymis, prostate, sperm cells, ovary, uterus, oviduct, preimplantation embryo, placenta, embryo, fetus and neonates"
It is thought that in sperm, the anandamide prevents the acrosome reaction, therefore preventing the sperm from activating before it reaches the female tract and also preventing polyspermy during fertilization. The question is, how much anadamide (AEA) is there in reproductive biological fluids?
"We detected AEA, OEA, and PEA in human seminal plasma, mid-cycle oviductal fluid, and follicular fluid analyzed by HPLC/MS"
And the sequela, how much of that stuff do you need to feel a buzz?
"Oral administration of AEA and 2-AG to mice can produce psychotropic effects, suggesting that these endocannabinoids reach the brain ( Di Marzo et al., 1998)."
A quick survey of the literature suggest that 5.8mg/kg is the ED50 of AEA to impair working memory performance (i.e. get a mouse high). So a rough approximation of the dose of milk for an infant to feel the effects is 20,209 L of milk, or for a woman to get high of seminal fluid she would need to chug a good 62,142 L. Notice that calculating the converse would be morally reprehensible.
I suppose the fact that it's so dilute is a good thing for the baby since: "Newborn humans, that had been exposed to marijuana prenatally, exhibit increased tremors, exaggerated responses to stimulation, and spend less time sleeping quietly ( Fried and Smith, 2001).".... but it fails to explain why babies have such munchies...