Well, they do a lot of research on herbs and such, so, they do know what they are speaking. That was just one article, they are numerous ones out there and they all say the same thing. Naturally, ALL foods should be eaten in moderation and when possible, in the organic state with no pesticides, etc.
With due respects, the statement by the American Botanical Council is meaningless. It is also irresponsible. It reminds be of the 1930's advertisements to drink radioactive water because it's "good for you". Then again there are agricultural interests at stake. There are also those who believe the earth is flat and the moon is made of green cheese.
A better question would be to assess the seriousness of the risk. In reality, it is minimal. I would not be concerned about eating a single meal. Just don't eat the skins.
The role of nightshades in inducing birth defects in livestock and experimental animals is a known fact. It must be remembered that these animals are fed large quantities of nightshades. To produce "sheep's eye" requires an almost exclusive diet of potato skins.
In addition, the toxins are in the skins, which are not normally eaten when consuming plantains.
Millions of people around the world consume the skins of nightshades, but there has never been a systemic study with control groups. There have been such studies with animals, and the incidence of birth defects is well-substantiated. The risk increases with the quantity of toxin.
For that reason tomatoes have been selectively bred to reduce drastically the toxins in the skins. This in turn makes the tomato more vulnerable to insects and the use of more insecticides.
An article on plantain by the American Botanical Council written in 2000 states that there are no restrictions known for use during pregnancy or lactation and no known interactions with drugs. (“Plantain.” American Botanical Council, p. 3)
That is an excellent question.
Some forms of plantain are nightshades. Nightshades contain a neurotoxin which is mutagenic in the outer skins. Nature developed these toxins to kill insects that try to eat the plant. If sheep are fed large quantietes of potato skins, for example, the offspring sometimes develop a birth defect involving a single eye.
That being said, modern agricultural methods have developed plants which have much lower doses of toxin. The tomato of 1750, for example, contained more toxins in the skin than the tomato of 2010. That was why in traditional recipes the tomatos were skinned (peeled) before using in sauce.
The toxins are primarily within in the skins and not within the interior of the plant, however prudence would suggest that nightshades be avoided during pregnancy.