Is there such thing rash appears on pregnant women that itches an nothing will help?

PUPPP: Pruritic urticarial papules and plaques of pregnancy (puppp), also known as polymorphic eruption of pregnancy, is the most common rash in pregnant women. It normally occurs in first pregnancies during the third trimester with an average onset of 35 weeks. Thankfully, puppp does not usually affect subsequent pregnancies.

Pregnancy rashes: Some pregnancy conditions can be very itchy. Puppp comes at end of 3rd trimester, usually starts in stretchmarks and can have "hives" like rash and small blisters. Pemphigoid gestationis also has "hive" like rash and may have blisters, usually starts in 2nd trimester, may have consequences for baby so must be treated. Cholestasis may not have any rash just itching. See your dermatologist asap.