It sounds like the itchy skin is near stretch mark areas because you said only in pregnant growing areas.
If it is o.k. with your doctor, then try benadryl topical cream for the itching or OTC hydrocortisone cream. they should both stop the itching fairly quickly. I don't know what is on your doctors list of meds that are ok during pregnancy. my doctor was really strict with all OTC, even claritin. You can also try oral benadryl, claritin, or zyrtec. but ask the doctor first. You may not have allerigies but they should help with the itching. the creams should help whether you have any allergies or rash also. you should also try vitamin-e oil. drink plenty of water to keep your skin hydrated. ice packs can also take the itch out. i use those myself when i have a rash. the ice/cold stimuli interupts the itch stimuli to your brain, and the cold numbs the area to boot. but don't leave on for more than 10-15 minutes then break and then do it again. you don't want frost bite. you can also put a large bandaid over irritated chafed skin to give it a break, from say a waistband rubbing and giving you that raw, sun-burned feeling. also don't take HOT showers, only luke-warm. the heat irritates skin sometimes also. oatmeal bath soaks help. olive oil with a couple drops of teatree oil might help also. and I do use RENEW also. it is from a great company. i don't sell the product either, but it is a godsend. i love that stuff. and it works well for contact dermatitis and eczema. and it doesn't burn at all.
hope some of these ideas help. In case you haven't guessed we have alot of skin issues at my house.
good luck.
L.