Pregnancy is a challenge for the mother's immune system from the outset. Half of the genes in the foetus are foreign to her body. The immune system has to strike a balance between tolerating the foetus and protecting the mother and foetus from infections. Throughout the pregnancy, an immunological balance takes place between mother and child. At the Norwegian University of Science and Technology's (NTNU) Centre for Molecular Inflammation Research (CEMIR), a research group is engaged in studying inflammation in pregnancy. The group has made findings that shed light on how the immune system behaves during pregnancy. The researchers found that immune activity in normal pregnancies follows a certain pattern, with elevated immune activation in the first three months, then a calmer phase the next three and higher activity in the last three months, especially when childbirth is imminent. Another finding was that women who had given birth previously clearly had higher immune activation at the beginning of their pregnancy, but lower than first-time mothers as labour approached. Women who went over term had particularly strong immune activation, which might indicate stress.