Rh Negative Blood Explained: What the + and − Mean
Updated 2026-11-07T00:00:00.000Z
The plus or minus after your blood type is the Rh factor, more precisely the RhD antigen. If your red blood cells carry RhD you are Rh positive (A+, O+…). If not, you are Rh negative.
How common is Rh negative?
| Population | Rh negative (approx.) |
|---|---|
| Europe, US (European descent) | 15% |
| Africa | 3–8% |
| India | ~5% |
| Korea, Japan, China | under 1% |
The Basque population in Spain and France has one of the highest rates in the world, around 25–35%.
How it is inherited
Each person has two Rh genes, one from each parent. The positive gene (D) is dominant, the negative gene (d) is recessive.
- DD or Dd → Rh positive
- dd → Rh negative
So two Rh-positive parents can have an Rh-negative child if both carry a hidden d gene. Two Rh-negative parents will always have an Rh-negative child. Try it in the baby blood type calculator.
Why it matters in pregnancy
If an Rh-negative mother carries an Rh-positive baby, her immune system can make antibodies against RhD, usually after blood mixes at birth. In a later pregnancy those antibodies can cross the placenta and harm an Rh-positive baby, a condition called haemolytic disease of the newborn.
This is now largely preventable. Doctors test blood type early in pregnancy and give Rh-negative mothers an injection of anti-D immunoglobulin when needed. If you are pregnant and Rh negative, your midwife or doctor will explain the schedule.
Transfusions
Rh-negative people should receive Rh-negative red cells. That is why O− is so valuable for emergencies and why blood services often ask Rh-negative donors to give regularly. See the donation compatibility chart.
General information only; ask a health professional about your own situation.