thanks for this interesting question! Diatomaceous earth is a compound made mostly of fossilized remains of hard shelled algae. It has a powderlike consistency. It is used mostly for the treatment of parasites, yeast, and intestinal concerns. There are different grades of diatomaceous earth, in the food grade it is comprised mostly of amorphous silica which is the safe type. Other lower grades may contain the type of silica that can cause silicosis. Most of the earth you buy at the health food store is the higher quality food grade and thus is quite safe from what we know. It is not well absorbed in the body and appears to be mostly excreted through the stool, having most of its action in the intestine.
As to using it in pregnancy, currently there isn't any evidence for diatomaceous earth in the perinatal period. When it comes to IVF and pregnancy I always try to err on the side of caution and because it does contain silica it might be best to avoid it while going through cycles/pregnancy.
I hope that this is helpful and good luck with your cycle!