If a kid grows up and has nut allergies (or food allergies of any kind), would it have been possible for that kid to have an allergic reaction if the mother ate that food while the baby is in utero?
Surprisingly, not that much is known about food allergies. My son has been part of the HealthNuts study for the past 3 years where they track 5300 kids with allergies. In those three years, they have reversed some of the previous recommendations. A recent NY Times article discusses some on the latest research into the effect the mothers immune systems has on autism and allergies.
As to your specific question about in utero reactions, I do not think the scientific community has the complete answer yet.