The paper summarizes the results of follow-ups of 40 pregnant women with luteal phase deficiency (LPD) who are treated with a transdermal Progestogel system. Gestagen deficiency during pregnancy causes different breast pathological processes initially at the functional level and then leads to proliferative and dysplastic manifestations in the epithelium of ducts and lobes. Conventional hormone therapy slightly affects breast processes in the patients with LPD. During progestogel treatment, lobar hyperplasia was reversed and disappeared by the beginning of the third trimester in all the patients. The trends in benign breast tumors did not differ in both the women receiving progestogel in combination with gestagens and those treated with only utrogestan.