K.N.
It sounds like you have an allergy to nickel. White gold and 9% gold contain nickel; solid gold (and silver) do not.
I found the following explanation:
"10 to 12% of the female population and 6% of the male population are estimated to be allergic to nickel. In fact the allergy is not caused by nickel itself but by the nickel salts which are formed from perspiration in contact with the piece of jewellery piece or watch. This phenomenon is always accompanied by corrosion of the object."
I suppose it's possible that being pregnant with a particular sex could change the chemicals/hormones in your sweat... which could then increase the nickel salts created when wearing your ring. Or, you might have been previously pregnant at a time of year when you sweat more than now-?
However, if you have developed a dermatits previously, you should consider avoiding all nickel containing metals/objects... Which means you may need to replace your wedding band with a pure gold (or platinum, if you don't want a gold color). Otherwise, your next reaction could be worse... Never know.