"I'd had a routine pregnancy blood test when my doctor told me I was 'Rhesus negative'."

When I found out I was pregnant for the first time, I did what I usually do when faced with a new situation: ask five million questions and make sure I have every step-in place to ensure everything can run as smoothly as possible.

As any woman who has been pregnant before would know, early pregnancy involves many tests, particularly of the blood variety.

One of the routine blood tests on the long pathology request form was to determine my blood type.

In my appointment to discuss the results, my obstetrician Dr. Patrick Moloney informed me that my blood type was ‘negative’ (as in its type not that it is was some sort of depressed or dodgy blood) and because we already knew my husband’s type was ‘positive’, it meant I was at risk of ‘Rhesus disease’.

*Cue the mental freak out*

Firstly, WTF (I didn’t say this out loud) is this disease I have never heard of? And why am I at risk of it?

Dr. Moloney explained, “When a Rhesus negative woman has a baby with a Rhesus positive man, the foetus inherits the Rhesus marker (the negative or positive) from the father and is therefore Rhesus positive.

“If a bleed occurs during the pregnancy and some Rhesus positive foetal blood leaks into the mother’s circulation, the mother sees the Rhesus positive cells as ‘foreign’ and develops an immune response against Rhesus positive red cells.”

These are all the things pregnant people never say. Ever.

Video by MMC

All I could hear in my head after this explanation were the words “foreign” and “immune response against”. Alongside these words, my mind envisioned angry faced cells with pitch forks attacking my baby.

Obviously this freak out and over exaggeration was quite evident within my facial expression, so Dr. Moloney was very quick to tell me that it is quite manageable and low risk when following the correct processes.


This natural reaction from the body to fight off anything foreign (thanks for having my back, body) doesn’t actually impact the current pregnancy, but it can with any subsequent ones.

Dr. Moloney said, “by the next pregnancy the mother has developed a mature immune response and her immune system will attack the Rhesus positive red cells in the foetus.

“The baby becomes anaemic and sick and needs careful monitoring and an in-utero blood transfusion can be required in severe cases if the baby is to survive. The baby can also be born anaemic and jaundiced.”

Despite this scenario sounding completely full on and utterly scary, the fact is, only 15 per cent of women are Rhesus negative (lucky me). Although it can potentially have severe implications and has been a “big cause of recurrent pregnancy loss” in the past, this is no longer the case *sigh of relief*.

“In the 1960s, a preventative treatment was developed called Anti-D. This is an injection taken by a Rhesus negative woman in pregnancy that stops her immune system developing an immune response to Rhesus positive cells. This came into widespread use in the 1970s and has largely eliminated Rhesus disease in the developed world,” Dr. Moloney said.

If you are Rhesus negative and your partner is positive, the treatment is pretty easy and straight forward.

“Anti-D injections are given routinely to Rhesus negative women at 28 and 34 weeks of pregnancy. Additional doses are given during the pregnancy if something happens to increase the risk of a bleed from the baby to the mother,” Dr. Moloney said.

“An extra dose is given to the mother after the birth if the baby’s cord blood test confirms the baby is Rhesus positive. All of this will prevent Rhesus disease happening in future pregnancies.”

The good news for Rhesus negative women out there is other than a few extra needle jabs along the way, the likelihood of it impacting you or your pregnancy or future ones is minimal.

Dr. Patrick Moloney is an obstetrician and gynaecologist in Ballarat, Victoria.

Shona Hendley is a regular contributor to Mamamia and a freelance writer from Victoria. Shona has a passion for animal welfare, education and raising her two daughters. You can follow her on Instagram.