Skin rashes that occur during pregnancy can be non-specific (such as due to allergies, medicines, insect bites, skin infections, viral infections, parasites, tumours) or rashes specific to pregnancy called as specific dermatoses (skin disorders) of pregnancy.
The various examples of pregnancy rashes are PUPPP - (pruritic urticarial papules and plaques of pregnancy), papular dermatitis of pregnancy, prurigo gestationis, herpes gestationis and rarely impetigo herpetiformis.
Since you have a childhood history of eczema, it may be a form of eczematous rash in your case or may be prurigo gestationis. The latter occurs in two forms, the early onset where the rash is seen on the upper trunk and upper parts of arms and legs and a late form, which affects the abdomen, usually on striae (stretch marks).
You should consult a doctor for an early advice on diagnosis and treatment of the condition. A skin biopsy may be required sometimes to detect the exact nature of the lesions.