Altered interleukin 12 and nitric oxide levels in recurrent miscarriage.

The causes of recurrent miscarriage are not fully understood. Recent studies have suggested that whilst a TH 2 type immune response may be associated with a healthy pregnancy, miscarriage may be associated with a TH 1 type response. Serum levels of nitric oxide (NO) and Interleukin 12 (IL 12) were measured in; healthy non-pregnant women; healthy pregnant women; women suffering spontaneous abortion; pregnant women with a history of recurrent miscarriage; non-pregnant women with a history of recurrent miscarriage. Normal pregnancy was associated with a significant decrease in serum levels of nitrite (13.0 vs. 22.0 P < 0.0001). In women admitted with spontaneous abortion there was a significant increase in the levels of nitrite (16.0 vs. 13.0 P < 0.05), but no change in IL 12 compared to normal pregnant women. In pregnant women with a history of recurrent miscarriage levels of nitrite (16.0 vs. 13.0 P < 0.05) and IL 12 (10.0 vs. 6.0 P < 0.0006) were significantly elevated compared to normal pregnancy. When these women were sampled prior to becoming pregnant the levels of NO were found to be significantly lower than those in the non-pregnant control group (13.1 vs. 22.0 P < 0.05) although levels of IL 12 were unchanged. No correlation was found between serum nitrite and IL 12 levels. This report further supports the idea that polarisation of the immune response during pregnancy may predispose to recurrent miscarriage.