Is it this?

PUPPP
The term "PUPPP" refers to a condition called pruritic urticarial papules and plaques of pregnancy. Occurring in about one of every 150 pregnancies, PUPPP is characterized by itchy, reddish, raised patches on the skin. These usually show up first on the abdomen and often spread to the arms and legs. In some women, the itching can be extreme.

Although PUPPP can be quite uncomfortable for the mother, it does not cause a risk for the baby. It is not known for certain what causes PUPPP, but there appears to be a genetic factor involved because it tends to run in families. Unlike so many of the other symptoms of pregnancy, PUPPP does not seem to be linked to increased hormone levels. When it occurs, it is nearly always in first pregnancies, and it rarely recurs in subsequent ones. Treatment of PUPPP consists of oral medications or anti-itching creams that are applied to the skin. Oatmeal baths or baking soda baths may also provide some relief. The rash-like symptoms of PUPPP will go away after delivery.

hi there i had the same sort of thing. Pinetarsol helps a bit i was given as antihistamine cream and tablets and the combination of all three helped so i could at least function. I had it down my arms legs it started in the stretch marks on my tummy. 5 mins after my bubba boy was born the rash was gone. i wish you the best of luck with ur new bub.