Because pregnant women are told to eat extra servings of leafy greens for the folic acid and iron content.
Leafy greens are like the miracle pregnancy food, all the right nutrition, fiber for constipation (a chronic pregnancy issue), doesn’t make you fat and of course to avoid chemical pesticides, you need organic!
Nobody tells you to increase your soy, corn or wheat intake. Potatoes are out permanently as the skins can contain a naturally occurring bio-toxin that may cause spina bifada. Too much seafood - mercury poisoning, blah, blah, blah.
As a former frequently pregnant woman, I know exactly what they tell you and what we tell each other. Spinach, kale, collard, mustard, turnip greens, cabbage, broccoli, brussel sprouts, cooked, raw, chopped, with or with out low fat dressing.
Pregnant women are the ultimate foodies.
Something has to account for the large difference between pregnant and non pregnant women and it’s most likely going to be differences in diet.
That could be, but my only point about the leafy greens is that most are not grown organically, and would not have been grown using Bt. So it's very unlikely more than a very few of the women in the test groups were eating organically grown greens. - They would not have ingested the Bt from the non-organic greens most would have eaten.
Unless Bt has replaced pesticides like Sevin for non-organic farming of greens, then the greens don't answer your question.