What Is the Rhesus Factor?

Blood groups in the Rhesus Factor system.
People with any blood type can receive type O blood.
Article Details
  • Originally Written By: M. Dee Dubroff
  • Revised By: A. Joseph
  • Edited By: Lucy Oppenheimer
  • Last Modified Date: 04 November 2014
  • Copyright Protected:
    2003-2014
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The Rhesus factor, also known as the Rh factor, is an antigen that exists on the surface of red blood cells in most people. People who have the Rhesus factor are considered to have a "positive" (+) blood type, such as A+ or B+. Those who don't are considered to have a "negative" (-) blood type, such as "O-" or "AB-." The Rhesus factor gets its name from experiments conducted in 1937 by scientists Karl Landsteiner and Alexander S. Weiner. Their experiments involved rabbits which, when injected with the Rhesus monkey's red blood cells, produced an antigen that is present in the red blood cells of many humans.

The ABO Blood Grouping System

Although there are at least 30 different systems for grouping blood types, most people are familiar with the ABO system, which groups blood into four general types: A, B, O and AB. Each blood type is usually further labeled as positive or negative, which is a reference to the Rhesus factor of the blood. More than 85% of people are Rh+.

The Rh Factor and Antigens

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The Rh blood grouping system actually involves more than 50 antigens that are found on the surface of red blood cells. These antigens are proteins that, when introduced into a body that does not have the same type, can cause the person's immune system to respond by producing antibodies that attack the proteins. The Rh factor, Rh+ and Rh-, usually refers specifically to the presence or absence of one of these proteins — the D antigen. The D antigen tends to cause an especially strong immune response in people who do not have it.

There are two alleles, or genetic variants, of this antigen: D and d. A person who is Rh- has two recessive variants, dd. Anyone who has at least one DDD or Dd — is Rh+. As with most genetic traits, one allele is inherited from each parent.

Rh Type and Pregnancy

A person's Rh type is generally most relevant with respect to pregnancies. During pregnancy, an Rh+ fetus developing in the womb of an Rh- woman runs the risk of developing Rhesus disease, also called Rh disease or hemolytic disease of the newborn. Only Rh- women risk having children with this disease; an Rh+ woman can carry an Rh- child without developing this condition.

For an Rh- woman to have an Rh+ child, the father must have been Rh+. An Rh+ man has at least a 50% chance of passing on the Rhesus factor to the child; a Dd father could pass either the D or d to his child. If the father is DD, there is a 100% chance that the child will be Rh+.

If the mother is Rh- and the child is Rh+, and if the child's blood enters the woman's bloodstream during pregnancy, labor, or delivery, the woman's immune system might respond by producing antibodies to fight off the child's antigens, which are foreign to the woman's system. That is, the woman's body might naturally produce antibodies that attack the baby's blood, causing the baby's red blood cells to break down. The result of this incompatibility will not affect the health of the mother, but it can affect the child's health. Potential health problems include jaundice, anemia, and brain or heart damage. In severe cases, Rh disease can be fatal to the infant.

Sensitization

To protect itself from the rhesus factor, a Rh- woman's body usually first becomes sensitized to the D antigen. This means that her immune system has been exposed to the protein, and has started to produce antibodies to fight it. Rhesus disease is less likely to affect an Rh- woman's first-born Rh+ child, because the mother and child's blood usually does not mix until labor and delivery. At that time, the mother's body may not have had the time to make enough antibodies to cause serious problems.

Once the woman's immune system has responded to a child's antigens by producing antibodies however, those antibodies will be present in the mother's system for the rest of her life. The potential for Rh disease increases with each subsequent pregnancy, because the antibodies will be present throughout the duration of each pregnancy after they are first produced.

Protecting Against Rh Disease

There are preventative measures to protect against Rhesus disease and its effects. Women should be tested early in their first pregnancies to determine if they are Rh- and if they are sensitized. Sensitization might occur not only through normal pregnancies, but any time a woman and her child's or fetus' blood mix, including miscarriages, ectopic pregnancies and blood transfusions.

If a pregnant woman is Rh- and has not yet been sensitized, she usually will be given an injection of a blood product known as Rh immunoglobulin about seven months into the pregnancy. This should prevent sensitization for the rest of the pregnancy. The Rh immunoglobulin shot seeks to destroy any Rh+ antigens produced by the baby and present in the mother's bloodstream before the mother is able to create antibodies. Additionally, it generally is recommended that the newborn be tested for his or her Rhesus blood type.

When the child is Rh+, the mother is often given another Rh immunoglobulin shot shortly after birth to prevent her from becoming sensitized. Rh immunoglobulin injections last only for a given pregnancy. Subsequent pregnancies will likely require separate Rh immunoglobulin injections. This treatment works to prevent Rh disease in 99% of cases.

If the woman is Rh- and has been sensitized, the injection will not help. Close monitoring of the baby typically is conducted to ensure that Rh disease is not developing. Blood transfusions to replace the damaged blood with healthy blood might be given during or after delivery, depending on the circumstances.

Blood Transfusions

Although the Rh factor is most often discussed in reference to pregnancy, it does play a role in other health matters. Just as a woman's body can develop antibodies that attack her baby's blood, a patient who is Rh- can have a transfusion reaction — an allergic reaction to the blood — if he or she is given blood from an Rh+ positive donor. Such reactions are relatively uncommon because blood is screened for the Rh factor, and Rh- patients receive Rh- blood during a transfusion whenever possible.

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Discussion Comments

anon122167
Post 47

what happens to the male and female baby if both father and mother are o positive or one is negative and one is positive.

anon118281
Post 45

I have a friend that isn't sure if he is the father to their one year old son. she is a- and he is o+ and the baby is a+? can anyone help me out here?

anon103197
Post 44

is it possible to have a RH negative child when both parents are positive?

anon101484
Post 43

I am not sure how this works, but I was wondering if me and my partner have anything to worry about? I am A+ Male and she is a O- female. I know if a female who is O negative has a child with a male with O positive blood then the Rh factor can be a problem but is it still a problem in my situation? If not is there other problems? I am on a slow computer so I have problems searching for things.

juliet
Post 42

we had a child in 2006 and I am find it had to conceive. Last year i had a miscarriage and up until now nothing is happening. We went to the clinic and were told that I'm rh negative while my husband is positive and that it is now too late to take the injection. What do we do?

anon83068
Post 40

I am confused. when i was born they said i was O+, and when i was 22 i became pregnant with my first child and was told that i am actually O-. Both of my parents are O+, and I've been told that it is not possible for your rh factor to change.

Please help me to figure this out. (please know, i am an army brat, so I've been to hospitals in three diff countries. Is it possible for them to all make the same mistake? or is it really possible for my rh factor to change?)

anon68533
Post 38

to thiru: obviously she should go for RhIg injection since she is rh negative. or else if her child will be rh positive so her blood will produce antibodies against the child's antigen which will be harmful for child's health. prevention is better than cure. take care.

anon62213
Post 37

i have five children. the first and third are Rh negative, while the other three are Rh positive. My husband is Rh positive and i am Rh positive. However, i learned that i had an autotransfusion after my birth in 1952 at Manchester when i was a toddler in relation to Rhesus Factor. I don't really understand what happened.

anon57201
Post 36

Are there complications when only the woman is negative or is is vice versa? That is, what if the man is negative and the woman is positive?

anon55041
Post 35

Hi i am rh neg and had 3 miscarriages in the last two years. i am pregnant again and i read everywhere about the rhlg shot and even spoke to my doctor, but it seems that they don't want to give me the shot. i am afraid of losing this baby again.

what should i do and can my baby be born abnormal or what? Please help -- do i have to get the shot or what?

anon53997
Post 34

Can any one help in this? I have B+ve and my wife is B-ve blood group. This is her first pregnancy and she's around two months along.

Will my baby be born with problems because of this Rh factor? do i need to suggest she go for (RHiG) injection during her seventh month of pregnancy? will this rh factor affect my wife's health?

please help me in this..

thanks

Thiru

anon51253
Post 33

To schu: The answer is no. A child is cannot be type o blood if either the parents are not. That's why blood types used to be a main factor in disputes of paternity when testing for DNA was not yet performed. I hoped this helped.

MissJoy
Post 32

I am an A negative female and my partner is O positive. We want to have a baby, but we would also like to know everything we can about our blood types. We would also like to know if we could have more than one healthy child. Any and all answers will be much appreciated! Thank you

chilli
Post 31

I am 0+ male and my fiancee is O- female. i know about the rhesus incompatibility. i would like to know if this can be completely taken care off by proper treatment.

anon44897
Post 30

the only way you could have complications is if the mother is RH - but that is why there are blood tests to determine blood type early in pregnancy so then once you reach 26-28 weeks they give you a shot to keep it from attacking the baby. it is okay to have a RH- and be pregnant.

anon41562
Post 29

what if both parents are positive(father is O and mother is B). is it possible to bear a child who is negative( B-)?

anon41236
Post 28

im rhesus d negative and my partner is rhesus o negative. would that complicate any pregnancies?

anon41199
Post 27

If o+ men marry an A- girl, is there any problem for child?

abena
Post 26

Can a woman with o+ marry a man with o+ without any child bearing problems?

anon35915
Post 25

If me and my husband are A+ will there be any problems in pregnancy

avie
Post 24

i'm rh negative & my husband rh positive. our first baby died; a newborn. it was rh positive. it died of a lung hemorrhage. kindly inform me if the rh factor could be a danger for the next baby. precautions recommended.

premahuja
Post 23

Is it possible for a couple, both of whom are Rh+ to have Rh- child?

Thanks

satishpgoyal
Post 22

I have B negative bld grp and very soon going to marry. She has A positive bld grp. Plz tell me will there b any complication in our child?

anon25317
Post 21

What if the woman is rh+ and the man rh-, what is the result of their children?

anon22904
Post 20

I am O+. After I delivered my third baby, I was told that my body produced antibodies (anti-c)! Which was odd. How is that possible?

markc
Post 19

Hi can anyone help? if my wife is rh o- and i am ab + is it possible to father a child with a- blood

thanks m ...

danielfarina
Post 18

is it possible to change my blood type from ab+ to ab-? if so, how?

anon16055
Post 17

Can a RH-negative father and a RH-positive mother bear children without complications?

Kris3065
Post 16

I am A+, my husbands blood switches between + & -. When my son was born they had to test his blood many times and finally determined that he is a positive donor but a negative receiver. What causes this? Is it likely to cause him any problems?

momma303
Post 15

My daughter is 0- and her husband is +. She had a miscarriage about a year ago and didn't know that she should have been checked for antibodies. She is now pregnant and everything looks good, but the doctor does not want to see her until her 8 to 10 week check-up. Should she insist on being seen earlier and what are the chances that she became sensitive? Her miscarriage was @ 4 to 6 weeks.

olivia
Post 13

There are numerous factors in calculating blood types and unfortunately we can't provide that service here on wiseGEEK. But, if you input "blood type calculator" into your search engine, several easy-to-use choices come up!

malena
Post 12

Here are the possibilities:

If one parent is Rh positive and the other is Rh negative, the child could be either Rh positive or Rh negative. The only way to know is to test the child's blood type.

If both parents are Rh negative, the child will necessarily be Rh negative.

If both parents are Rh positive, the child could be either Rh positive or Rh negative. This is because people have two alleles going to their Rhesus factor. Rh positive people can have two Rh positive alleles, or one positive and one negative while still being classified as positive. If at least one of the positive parents has a negative allele then that negative factor can be passed on to the child. A Rh negative person, on the other hand, necessarily has two Rh negative alleles.

justd2006
Post 10

Can a mother with O- blood and a father with A positive have an O+ child? in school I was told this is not possible- is this true?

Shayna
Post 9

Can two O+ parents have an O- child?

renukrs
Post 7

can a woman with A1 positive marry a man with O negative? will she face any problems with during the pregnancy???

anon1382
Post 5

can a lady who is O negative and shorteye sighted marry a man who is o positive and also short sighted.

what is/are the possible effect on their children?

is it advicale for them to get married?

Dayton
Post 4

Yep, that is certainly possible. If the father's blood type is AO+- (which would appear as an A+), he could give the O- to his child, who would also receive an O- from the mother. The only way to have an O- blood type is OO--.

anon1337
Post 3

If the mother is O- and the father is A+, is it possible to have a child with O-?

Dayton
Post 2

Interestingly enough, that IS possible. Essentially, one parent would have to be AO+- (which would appear as A+), and the other BO+- (which would appear as B+). The child could receive an O and an - from each parent.

Genetics at work!

schu
Post 1

If one person has A positive blood and the other has B positive blood, is it possible for their children to have O negative blood.

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