Need a reason why science is amazing? I’ve got one for you. In 1940, the blood from Rhesus monkeys helped find a factor in the blood that plays a critical role in maternal and fetal health, greatly increasing the chances of a healthy pregnancy.
It’s called the Rh factor (Rh after rhesus, get it?).
What Is It?
The Rh factor is one of many antigens that protect your blood cells from foreign or internal substances. However, the Rh factor can be a complication in pregnancy.
How Does It Work?
You can either be Rh negative or Rh positive (antigen is not present in your blood vs. antigen present in your blood). You’re tested for this blood factor between 24-28 weeks or if you decide to have an abortion. If you’re Rh positive? You don’t have to worry about it. However, if you’re Rh negative, it’s a problem.
Your Rh negative factor is usually not a problem in your first pregnancy as very little blood between the mother and the fetus is exchanged during the pregnancy. But maternal and fetal blood can be exchanged during the delivery or during an abortion procedure – and that’s where the Rh problems come in.
If you’re Rh negative and your partner is Rh positive, there’s a 50% chance that your fetus is Rh positive. (Scroll down on this link from the Mayo Clinic to see a helpful chart for how this all works.) So, when your Rh negative blood mingles with the fetus’ Rh positive blood, your own blood can produce antibodies that will attempt to repel your next Rh positive pregnancy by treating it as something that will harm you, sometimes resulting in miscarriage or by giving the baby a life-threatening illness, HDN (hemolytic disease of the newborn).
Luckily, we’ve got great medical remedies to solve the Rh problem.
What Can Be Done?
If you’re Rh negative, an injection called RhoGAM is given to you so that your Rh negative blood does not produce antibodies against your potentially Rh positive fetus. You’ll also receive another shot of RhoGAM within 72 hours of delivery if the baby is found to be Rh positive. You will also receive shots of RhoGAM in all of your subsequent pregnancies to make sure the problem is solved.
The Rh factor was once a leading cause of infant mortality, and today the problem’s virtually been eliminated from the developed world.
Isn’t science great?

Unfortunately, if people are not aware of this issue, it does still persist. I have a friend who recently miscarried. Because she was not aware of the Rh factor, she didn’t get the injection within the time frame required. This puts her future pregnancies at risk.
What a shame. At least they now know to look out for it in her future pregnancies, though I admit, that’s little salve on the current wound. -e