The antibodies that your body made in your first pregnancy can quickly multiply, cross the placenta and attack the blood cells of your baby (NHS BT 2016, NHS 2018). But it can cause problems if you become pregnant again with another RhD positive baby. Sensitising is not usually harmful if it is your first pregnancy. This is known as a sensitising event, or being sensitised (NHS BT 2016, NHS 2018). It will be treated as a foreign invader and your body will produce antibodies against it (NHS 2018, NICE 2008a). If some of your RhD positive baby's blood enters your bloodstream, your immune system may react to the D antigen on your baby's blood cells. Your baby's dad can have a blood test to check his rhesus status, if he’s not already aware of it from a previous health check, or from being a blood donor (NCCWCH 2008, NHS 2018). Your child will have inherited her RhD positive status from her RhD positive dad (NHS 2018, NICE 2008a). What does it mean if I'm rhesus negative?Rhesus status only matters if you are RhD negative and the baby you’re carrying is RhD positive (NHS BT 2016, NHS 2018). If you’re rhesus negative (RhD negative), you do not have the D antigen on your blood cells.If you're rhesus positive (RhD positive), it means that a protein (D antigen) is found on the surface of your red blood cells.Your rhesus status is fixed by your genes: One of these tests is to find out your blood group (A, B, AB or O) and your rhesus status (positive or negative) (NCCWCH 2008, NHS 2018). What is my rhesus status?When you have your first antenatal appointment your midwife will offer you a number of routine blood tests.

Where does anti-D come from, and is it safe?.

What happens if I already have antibodies in my blood?.

How could my baby's blood get into my blood?.

Is there a way to avoid having an anti-D injection?.

How does rhesus disease affect my baby during pregnancy and after birth?.What does it mean if I'm rhesus negative?.

Rh negative blood