Steroid hormones levels during pregnancy

Human leukocytes possess alkaline phosphatase (L13, 03, RIO, T6, V3, V4) whose activity parallels the concentration of certain circulating steroids. Thus, during the menstrual cycle, the leukocyte alkaline phosphatase evidences a peak at midcycle corresponding to the higher estrogen level. In the later stages of pregnancy the enzyme level increases. Corti-coid hormones also exert an effect on leukocyte alkaline phosphatase. 

Hormonal contraceptives are less reliable during the use of phenytoin and barbiturates such as phenobarbital and primidone. Intermenstrual breakthrough bleeding and spotting can take place, and pregnancies have occurred. Controlled studies have shown that phenytoin and phenobarbital can reduce contraceptive steroid levels. 

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