NoBlood

A colorless blood corpuscle whose chief function is to protect the body against microorganisms causing disease. These basically fight infection. Normal values 4.6 - 10.2 K/ul

doesit cross from mother to fetus?
if so is it an active transfer like immunoglobulins

No they don't pass from Mom to Fetus.

But they do pass from mom to baby by means of colostrum in the breast milk.Colostrum contains large numbers of antibodies called secretory immunoglobulin. Leukocytes are also present in large numbers; these begin protecting the infant from harmful virus and bacteria.

White blood cells pass through breast milk?

Yes they do ... the types of leukocytes that are common in colostrum are as follows
Neutrophil 50 %
Macrophage 40 %
Lymphocyte 10 %
So the breakdown of major components of colostrum are:
Immunoglobulins, Lactoferrin, Proline-rich polypeptide, Growth factors, Growth hormone, Leukocytes, Enzymes, Cytokines and lymphokines, Vitamins, Minerals, Glycoproteins, or protease inhibitors, Sulfer....etc
Just do a Google search on Colostrum and you can find out more information or go to wikipedia and get an overall view.