It is true...the risk goes up. It is higher when allergies already run in the family. Variation is the key. Any nut can be turned into a butter. Sesame and hemp butter taste good. A body craves what it knows. Figure out the main nutrition value of peanut butter and try other things that have the same nutrients in it. That will usually stave the cravings. I had gestational diabetes last pregnancy...hoping not to get it this pregnancy, but I am eating as if I did. This has some good info on vegan protien sources.
You can't just create an allergy just by eating something over and over. There has to be an underlying issue that triggers the allergy: ie gut health. In most food allergies, there is an unhealthy gut environment and when you introduce foods that have high risk of allergy (for various reasons) the larger particles are absorbed into the blood stream through holes in the gut and that triggers an allergic response. Could start off mild and turn anaphylactic with successive exposure. But in utero you aren't going to create an allergy. There's also a major diff between an allergy and a sensitivity. My 19mo DD has a major sensitivity to oats - gluten free or not, she breaks out in hives and turns red head to toe - but does NOT produce antibodies against the oats. So no, eating copious amounts of peanut butter in pregnancy will not create a food allergy.
Peanuts contain aflatoxin. A toxic mold. Google it and you may choose to eliminate it from you and your family's diet. People who crave peanut butter typically have a protein deficiency. Whey protein can help get through the cravings and also support a healthy pregnancy. Whey protein is also very good for the breast feeding mother and supports hormonal balance after birth. Don't take my word on any of this. Google or wikipedia Aflatoxin. Good luck!
Craving peanut butter when you are low on protein isn't a pathology-- it's just as natural as craving ANY high protein food when you are low on protein, or craving sweets when you have low blood sugar. Don't buy into this fear-mongering business about aflatoxin. I did look it up, and it looks like it require large amounts to create acute symptoms, and most humans are highly tolerant.
My feelings are that if you go down the road of eliminating and avoiding everything that *might* hurt you, I can't imagine that results would be a life worth living. I focus on the Big Toxins that we KNOW are harmful, and leave it at that.
As for me, peanut butter, apples and yogurt were the only wholesome foods I could regularly stomach in the first trimester, and my caregivers have been pleased to hear these remain staples of my diet.