The Immune System and Infertility

The immune system has two main mechanisms: cellular (type 1) and antibody (type 2). In normal pregnancy, substances produced by the placenta (particularly progesterone) cause a shift in how the mother’s immune system behaves so that it becomes ‘type 2 dominant’. This is because type 1 responses are potentially more dangerous for the pregnancy. This shift means that some autoimmune diseases that are predominantly cellular such as rheumatoid arthritis tend to get better during pregnancy. But it also means that antibody autoimmune diseases such as Lupus (SLE) can get worse, and specific antibodies can have their own harmful effects too – on both the placenta and the foetus.