Here are the ingredients:
Active Ingredient: Calamine, Zinc Oxide. Inactive ingredients: Bentonite, Magma, Calcium Hydroxide, Glycerin and Purified Water.
The only ingredient I'm unsure about is the calcium hydroxide. Calamine is a mixture of zinc oxide and iron oxide. It's considered safe by most OBs but hasn't been thoroughly tested which is why it's classified as unknown, I believe.
But some sites classify it as an antihistamine, which I don't get. But I also know that Benadryl cream is also viewed by most OBs as safe during pregnancy. But calcium hydroxide is pickling lime. It doesn't sound terribly healthy, but is also used in Native American cooking, so I don't know honestly. Other mamas might be able to give you more info there.
If you're uncomfortable using either, then I'd try to find something more natural and mint-based (though watch out for products like Sarna lotion, which contain essential oils but also have nasty chems). Or a colloidal oatmeal product.
I've used Benadryl cream during pregnancy. I've never used Calamine lotion during pregnancy because I've never needed to. It's a personal choice though, and when in doubt, call your OB/midwife and ask.
You could also try one of these home remedies:
To reduce itching, mix 1 tsp. of water with 3 tsp. of one of these dry ingredients; cornstarch, baking soda, or oatmeal. Make a paste and apply over the affected skin.
For cooling relief, apply over the itching area aloe vera juice, tofu or watermelon rind; they soothe and dry poison ivy immediately.
Calendula lotion is very good in reducing itching, limiting the spread of the rash and helping the body to heal faster. California Baby and Weleda both make great calendula creams.
You can also check out your local HFS for some homeopathic remedies.
Good luck, mama!