Rhesus Negative Factor in Pregnancy – Rh- Blood

Rhesus factor (rh) is a blood product – it’s a substance found in blood. Approximately 85% of the population has the rhesus factor and the remaining 15% percent do not. It is symbolised by the plus or minus after your blood group, for example, A- is rhesus negative and A+ is rhesus positive.

If you are a mother-to-be with rhesus negative blood (for example O- or A-), there are some things you might like to know if your partner has rhesus positive blood, (for example O+ or A+).

This does not apply to mothers with rhesus positive ( + ) blood or if your partner has rhesus negative blood, which does not pose any problem – you need not worry any further.

What If I Don’t Know Mine Or My Partner’s Blood Group?

When you first find out you are pregnant, your doctor/midwife/obstetrician may prescribe some routine tests. If you don’t know your blood group or if you’re unsure whether the doctor is testing it or not, just ask and this can be easily done.

How Can My Negative Blood Group Be A Problem?

If you are rhesus negative and your partner is rhesus positive, then your unborn child could inherit either negative or positive blood – you wont know until birth. However if the mother is negative and the baby happens to be positive (positive rhesus factor is dominant, negative rhesus factor is recessive), then this may cause problems for any future pregnancies the mother may have. Your first baby will be fine.

Problems can occur if the baby’s positive blood manages to find it’s way into the mother’s bloodstream, either during pregnancy or labour, mixing with her negative blood. If this happens and it is not treated, the mother’s blood can create antibodies to attack any positive blood, since it contains a ‘foreign’ component. This may cause anaemeia or in a worst case scenario, death. This means that any future pregnancies the mother has where the baby is again rhesus positive, her antibodies may cross the placenta and attack the baby’s blood cells.

How Can This Be Prevented?

Your obstetrician or midwife may organise a couple of blood tests throughout your pregnancy to monitor antibodies in your blood. It is important that the hospital where you birth your baby is aware of your rhesus negative blood, so they can test baby’s blood after the birth (from the placenta) to discover baby’s blood type. Should your baby have positive blood, you can choose to be given an “anti-D” injection within a couple of days following the birth. This prevents antibodies from forming.

If you experience any bleeding during pregnancy or if you have an amniocentesis, miscarriage, ectopic pregnancy or termination, you need to make your primary medical carer aware of this as soon as possible, as these may all pose opportunities for the blood of the foetus to mix with that of the mother’s and it will be unclear in most of those cases as to which blood group the baby belonged to. If none of these things happen, in a normal pregnancy, you will not need ‘routine’ anti-D injections until after the birth, should the baby’s placenta come back as rhesus positive – and if you choose to.

Some Obstetricians are now routinely giving Rh- women Anti-D injections without any blood tests to detect antibodies. However you might like to ask your doctor if this is really going to be effective or worthwhile if you have had no indication to suggest you have been bleeding. Not only is the shot of Anti-D a blood product (which involves risks in itself), but the chances that those routine injections (usually 2-3) will be given to you within 72 hours of possible bleeding – as required after possible exposure – which there has been no indication of bleeding anyway, is very slim. Your baby’s circulation is completely separate to yours so in a healthy pregnancy, the chance of the blood mixing is very, very slim.

Being rhesus negative myself and having had two children with my Obstetrician, I didn’t have bleeding during pregnancy so was never given preventative anti-D until after the birth, and everything was fine. I have certainly questioned the recent move to do these routine pregnancy shots.

What if I already have formed antibodies against positive blood?

The anti-D injection may not be able to protect you or your baby if you already have antibodies and you will need to be closely monitored by your obstetrician, possibly requiring specialist care. Discuss with your obstetrician.

If I have the anti-D injection will I be protected for good?

No – with each pregnancy the risk still exists of antibodies forming, should positive and negative blood become mixed. It is therefore important to make sure you continue to communicate your blood group with your future medical carers if you decide to become pregnant again.

Recommended reading on this topic: “Anti-D in Midwifery: Panacea or Paradox,” by Sara Wickham

Last Updated: February 23, 2015


Kelly Winder is the creator of BellyBelly.com.au, a doula, writer and mother to three awesome children. Currently, she's travelling the world for 12 months with her partner and children, and hopes to inspire more families to do the same. Visit aroundtheworldpluskids.com.au for more information.


  1. my comment is a question, and it goes like this, 12years ago I terminated a pregnancy and I am o rhesus(-). just until recently I read about negative rhesus factor in pregnant women and how it affects the un born baby. I just got married recently and believing God to be pregnant. am I at risk because I did not take that medicine to prevent the anti bodies from forming in my blood then because of my ignorance. what do you advice me pls?

  2. If am O-can my baby be O-and will I have a safe birth because my husband is O+ but have terminated a pregnancy before

    1. Your baby could be O negative or O positive. I am O negative and I had a miscarriage before my daughter and didn’t receive anti D injections I didn’t even know my blood type but I did go on to have a successful second pregnancy my daughter is now 3 and has positive blood.

  3. If am O-can my baby be O-and will I have a safe birth because my husband is O+ but have terminated a pregnancy before.

    1. Your baby could be O negative or O positive. I am O negative and I had a miscarriage before my daughter and didn’t receive anti D injections I didn’t even know my blood type but I did go on to have a successful second pregnancy my daughter is now 3 and has positive blood.

  4. I am O negative and have 2 pregnancies my first I miscarried and was unaware of my blood type and didn’t receive the anti D injection with my second I had a successful pregnancy and received anti D injections 3 times once at about 10 weeks due to a bleed due to sex and again between 28-36 weeks and one after my daughter was born with both pregnancies when I had sex I bled and now my boyfriend is afraid to have sex with me I am 13 weeks if I bleed after sex can it mix with my baby’s blood and cause me to form antibodies.

  5. Hi my blood group is b+ and my wife is O- now she is pregnant, will it cause any problem to my wife are my baby will delivery. Please suggest me what I can do to protect.

  6. I m a man of O +’ve and my wife is O -‘ve. We once terminated a pregnancy. Please does my wife needs Anti D or she can get pregnant since it has been some time now.
    Thank you doc

    1. She would need to get a blood test to see if she has any antibodies in her blood. If hers and the baby’s blood mixed, she could have formed antibodies, meaning she will need to be under watchful eye during pregnancy. But if there have been no antibodies, she wont need anything unless bleeding happens during pregnancy, and after the birth.

  7. My blood type is negative,my first baby was not a problem…how will this effect my second child as I am 4+ months pregnant now?

  8. For a woman who has the first pregnancy and she is A- while his husband is A+, after what duration of pregnancy will she be needed to have the anti-D injection ?

  9. Am O+ MY husband is B- ,I received the ant-D with in72 hours after delivery of my first born am now expecting the second baby but i can not afford that injection now becouse of financial crisis were in now,but am woried if my baby is safe

  10. What of people with has rh nagetive and have miscarried or aborted without been treated afterwards. Can they begin d treatment now?plss I really need to Knw.

    1. If they are already sensitised, then unfortunately you cannot reverse it. It requires specialist care for future pregnancies. A blood test will tell if they are or not.

  11. I have my beautiful little girl and I really want to have another child. I am rhesus negative. Is it possible to have a completely normal pregnancy even with the condition or will the baby always have to have blood transfusions and blue lights for jaundice? I also have cerebral palsy and i fell alot with my first child. being that I didn’t have a whole lot of help while I was pregnant and had to take the unleash trained dogs outside by myself and they pulled my down onto my belly. So my third question would be how hard of an impact would you have to have to cause bleeding? I told my ob that i had fallen every time and he never seemed concerned about bleeding. Please give me answers. i would love to have another kid but wouldn’t dream of bringing one into this world if it is just going to suffer.

  12. so I am a+ and my first daughter is being told she is o- she is now pregnant with her first and needs the shots. I don’t know my ex husbands blood type. Iis it possible for her to truly be o-.?

  13. My blood group isO+ and my husband blood is A+ then during pragnency or after child birth will there be any prblm please suggest

  14. I previously had a miscarriage at 6 weeks, almost 2 years ago. I’m now currently 7 weeks pregnant after 1 year of ttc. I only found out today, due to looking at my own baby book with my mum, that my blood type is o negative. I’m not sure what blood type my boyfriend is. I had a small amount of fresh blood bleeding at 6+1, and the midwife put it down to implantation bleeding. My scan showed a strong heartbeat and everything looked ok. Should I now be concerned that I’ve discovered my blood type, given my history of the miscarriage and being pregnant again?

  15. I am o- and my husband is o+. I had miscarriage march this year without any anti-D injection. now I am pregnant (6 wks) but bleeding. what is the cause? can I have a safe baby?

  16. I am 0+ and my husband is o- I hard miscarriage before and I am pregnant now. Is there going to be any need for me to be injected of anti rhesus.

    1. It’s likely the baby’s and your blood didn’t mix, but the easy way to find out is to ask your doctor to test for antibodies in your blood. If you don’t have them, you’re fine, but if you do have antibodies, your doctor will need to monitor the pregnancy.

  17. I’m O- and my boyfriend is O+ I terminated 1 month pregnant 3-4 years back with my ignorance, but I want to marry very soon and I don’t know the step to take in order to know my stand. Please I need your advice.

  18. Hello I need help, Im 25 weeks pregnant and A blood type with rh negative, I had an abortion last year and didn’t get an anti-D since I didn’t know my blood results then.Will my baby going to make it? #confused

Leave a Reply

Your email address will not be published. Required fields are marked *