Congratulations on your baby! All life is special and deserves to be celebrated. Antibodies can be a scary thing, but with a little help, everyone can understand them. Let's get started. This page is to teach you about the very basics of testing that will happen to you and your baby. With proper testing and monitoring, and a skilled medical team, you have every chance at a great outcome. If you're looking for something specific to your antibody, check over on the specific antibodies page, but only after you've read and understand this page. Remember to discuss all tests and their results with your health care team. Write down any questions that you have for them in your notebook. 

Prenatal Testing
Basic Prenatal Blood Work

  • No Antibody Found
  • Antibody Found
          Antibodies that ARE associated with hemolytic disease of the newborn

          Antibodies that are NOT associated with hemolytic disease of the newborn

Dad's Blood Work

Baby's Blood Work

NonInvasive Testing
Ultrasound Testing

  • MCA Doppler Assessment
  • Biophysical Profile (BPP)
  • Non-stress Test (NST)
Invasive Testing

Blood Work

Basic Prenatal Blood Work – What it Includes

For me, my basic prenatal blood work (performed at Borgess Hospital in Michigan, USA) included:

  • Blood type ABO type and Rh type to find out what my blood type is (for me it is O+)
  • Antibody screen aka Indirect Coomb's test (not to be confused with the Direct Coomb's that is run on baby after birth). This came back positive so they ran an antibody ID panel.
  • The Antibody ID panel came back positive for Anti-E for me. They ran 2 more tests, a test looking for the antigen E, and another test called an antibody titer.
  • The antibody ID panel, antigen test, and the titer are all isoimmune specific tests. If you don’t test positive for an antibody, you won’t have these tests run.
  • Complete Blood Count (CBC). This checks for how many white and red blood cells you have in general. It also measures Hemoglobin (Hgb), Hematocrit (Hct), and a couple other things. This and the tests that follow are not iso related, but are done to check the general health of the person.
  • An automated differential checking how many of each specific white blood cells I had.
  • The last part of the blood test was for immunology. They wanted to make sure I was indeed immune to rubella. Rubella can cause serious problems if a pregnant woman is exposed to Rubella and is not immune to it.
  • They also tested my urine to see if I was pregnant, had blood cells, mucus, bacteria, protein, sugar, etc. being secreted in my urine.

The most important parts of the blood test for the pregnant woman concerned about Isoimmunization are the blood type (ABO and Rh), Antibody screen, Antibody ID panel, Antigen ID panel, and the Titer. You can find some printables to add to your notebook to help keep track of all your results here.

No antibody found

A negative Indirect Coombs Test (also called an indirect agglutination test) means that your blood is compatible with the baby’s blood or that sensitization has not yet occurred (yay!). It checks to make sure that the pregnant woman has not developed antibodies against any potential antigen-positive blood of her baby. If sensitization has not occurred, in the case of Rh-D negative women, it can be prevented by a shot of Rhogam. See Interventions – Rhogam. This test should be repeated each pregnancy (3).

Antibody found

A positive Indirect Coombs test result means that your blood is incompatible. If you have a positive indirect Coombs test, it means you have already been sensitized and there are antibodies floating around in your blood. In this case, an identification panel and the antibody titer test should be done. The mother can be tested early in pregnancy to check the blood type of her baby by amniocentesis or free floating fetal DNA. If the baby has antigen-positive blood, the mother will be watched closely throughout the pregnancy to prevent problems to the baby's red blood cells. If the mother declines in-utero antigen testing for the baby, she will still be monitored closely throughout the pregnancy just as if the baby was antigen positive (3).

If you have ANY antibody that is not anti-D, and your blood type is A-, AB-, B-, or O-, GET YOUR RHOGAM!

There are many antigens. There is the Rhesus (Rh) group which includes D, c, C, e, E, and is the most clinically relevant (Note: no d antigen, pronounced “little d” exists so you will not find an Anti-d antibody.). However the non-Rh groups such as Kell, MNS, and Kidd have become increasingly more important as the incidence of Rh-D sensitization has decreased. Sensitization with Rh antibodies (c, C, e, E) is still responsible for the largest proportion of hemolytic disease in the newborn (HDN), followed by Anti-K, anti-D, anti-E, anti-Fya , anti-Jka (4).

Once you know which antibodies you have, you can find out if they are associated with hemolytic disease of the newborn (HDN). If an antibody is associated with HDN, additional blood testing occurs. While not all antibodies are included in the table below, these are some of the most common.

Antibodies that ARE associated with HDN

Diego: Dia, Dib

Duffy: Fya, Fyb*

Kell: K1, Kpa, k, Jsa, Jsb

Kidd: Jka, Jkb*
Lewis: Lea*, Leb*

MNS: M, S, s, N

Rh: D, c, C, Cw, e, E

Wright: Wra







PP1Pk (previously known as Tja)




Antibodies that are NOT associated with HDN*

Lutheran: Lua, Lub*

Wright: Wrb

















In the case of Anti-E antibodies, it is advisable to retest at 28 weeks to be sure that Anti-c has not developed.

*There have been cases of these antibodies causing HDN. Though rare, it does happen. Older lists available online will have these antibodies in the Does NOT cause HDN column, however this is no longer the case. Check the specific antibody page for more information.

Mom's Blood Work – Maternal Titers

What is it?
Titers are a measure of expressing the concentration. Your titers will help tell you how much of the antibodies are in your blood.

When is it done?

Depending on doctor preference, titers are done monthly, biweekly, or weekly. Some doctors will only do titers at the beginning and at the end, and will treat baby as affected, especially in the case of an already affected pregnancy. When you have your prenatal blood work, if your indirect Coombs test comes back positive, the lab should automatically titer it for you.

Where is it done?

Titers are done in the lab.

Why is it done?

Titers are done to help tell the doctor about how many antibodies are in your system, however they are not an effective monitoring tool when you have already had an affected baby, or in the case of some antibodies.

How is it done?

A simple blood draw is all that is needed for titers. Usually only 1 vial of blood is taken.

How often is it done?

Titers are drawn anywhere from once or twice per pregnancy, to monthly, biweekly, or weekly. It depends on the doctor's preference.

What do the numbers mean?

Your titers will come as a ratio. Such as 1:less than 1, 1:2, 1:4, 1:8, 1:16, 1:32, 1:1024, etc. This tells you how many times they need to dilute the blood to get rid of the antibodies. The higher the second number, the more likely baby is to be affected.

Large differences in titer can be seen in the same patient between different laboratories, and a newer gel technique produces higher titer results than the older tube method. Therefore, standard tube methodology should be used to determine critical titer, and a change of more than 1 dilution represents a true increase in maternal antibody titer (5).

When to get additional monitoring

You should have additional monitoring whenever you hit critical titer (1:16 for most antibodies, 1:8 for Kell), have a rise in titers, or have an antibody for which titers are not an accurate indicator of anemia.

What else should I know?
Titers can go up and down at random. Just because they are low now doesn't mean they'll stay low. Just because they are high, doesn't mean they'll get higher. Even having a cold can cause your titers to increase. 

Titers do not determine how baby will do after birth. Even moms with low titers, such as 1:2, can have babies at risk for brain damage from high bilirubin. Always get baby tested after birth, regardless of titer levels.

In the US they have now recommended that the 1: be dropped from the titer. So instead of saying 1:16, some places will just say a titer of 16. This is important because Quants (used in the UK and other places) are also shown as a number, but quants can include a decimal. Titers will never include a decimal, and will always be a 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, or 2048. Some places still report titers in the old way of 1:16, so we will continue to show them that way while also making a note about the decision to drop the 1: from the score.


To the left are titer tubes. In order to get the titer, each sample is taken and diluted by half. The last dilution that antibodies were detected in is the "titer". For instance, my antibodies were originally detected in the tube 1:1, but not when diluted by half (1:2), so my titer was originally 1:1. At one point my antibodies were detected in both the first tube and again after dilution, making my titer 1:2.

Dad's Blood Work

Once an antibody that has been associated with HDN has been found in Mom’s blood, paternal testing takes place to see what chance the baby or future children from the couple have of being affected. At our lab this was called the Rh Phenotype test and they only checked to see how many of the genes he had for the specific antigen (E) matching my antibody (Anti-E).

What is it?
An antigen phenotype is a blood test that is run on dad. 

When is it done?
The antigen phenotype can be run at any time, even if mom is not pregnant. This test is only run one time.

Where is it done?
The test is done in an outpatient lab. It can be ordered by any doctor. Dad's general practioner can order it, so can mom's midwife, OB, or the MFM specialist can order it.

Why is it done?

The antigen phenotype is run to find out what antigens dad has. It can help pinpoint the source of mom's antibodies. If mom has had a blood transfusion, this test is especially important because her antibodies may have come from the transfusion, and not from a previous pregnancy with dad. If dad is negative for the antigen that matches mom's antibody, then baby will be safe. 

What do the results mean?

We will use anti-E and the E/e antigens as the example. The results can be written in several ways. It may say E+e-, or homozygous E, or heterozygous. The results tell us if dad will pass on an at risk antigen, and if so, how often (100% of the time, or 50% of the time). The results will also tell us if dad cannot pass on the risk antigen which would mean baby would be safe. 

If Dad is heterozygous (E/e), then there is a 50% chance that the baby or future babies will be affected by that specific antibody. In this case, the fetus can be tested in utero or after birth. They may also say that he has tested positive for both the E antigen and the e antigen.

If Dad is homozygous dominant (E/E) then there is a 100% chance of the baby and future children being affected by that specific antibody. They may also say he tested positive for the E antigen and negative for the e antigen.

If Dad is homozygous recessive (e/e) then there is a 100% chance of the baby and future children NOT being affected by that specific antibody. They may also say that he tested negative for the E antigen and positive for the e antigen. 

Again, if dad is negative for the antigen that matches mom's antibody, then baby will be negative. If baby is negative for the antigen that matches mom's antibody, then baby will be safe. 

Baby's Blood Work

Ok, so this isn't specifically drawn from the baby, but it is about the baby. You can do cell free fetal DNA testing (cffDNA) to find out baby's antigen status. It can be so helpful and is something you can do while you wait to see the MFM specialist, or it is something you can request when you see the specialist. This test looks for small pieces of fetal DNA floating around in Mom’s blood stream. In some places (not common practice everywhere), a simple blood test drawn from Mom can tell about some of baby’s antigens. If baby is negative for the antigen that matches mom's antibody, then baby will be safe.  Unfortunately, cell-free fetal DNA testing for determining the genotype for other red blood cell antigens such as E and Kell is not yet available in United States. Tests are available in the US, UK, Netherlands, Canada, and Australia.  Check out the cffDNA page for more info. 


Noninvasive Tests

Ultrasound Tests - Ultrasound, MCA, and BPP.

Ultrasound Testing

What is it?

Ultrasound is an imaging test that uses sound waves to create a picture of how a baby is developing in the womb. It is also used to check the female pelvic organs during pregnancy (6).

When is it done?

Ultrasound can be done at any point in the pregnancy.

Where is it done?

Ultrasound can be done almost anywhere. It is frequently done in the doctor's office and doesn't require a special trip to the hospital.

Why is it done?

Ultrasound is used early on to establish correct gestational age. This is important for determining what the correct normal lab values are for the baby (amniotic fluid bilirubin levels, size of the baby, etc.). It is also used early to Confirm a normal pregnancy, determine the baby's age, look for problems, such as ectopic pregnancies or the chances for a miscarriage, determine heart rate, look for twins, and to identify problems with the organs (placenta, uterus, cervix, ovaries) (6).

Later on, ultrasounds are used to detect ascites and fetal hydrops. Ascites is the buildup of fluid in the space between the lining of the abdomen and abdominal organs. Fetal Hydrops is the end stage of hemolytic disease of the newborn where the baby has 1/3 normal hemoglobin or less. Both are severe complications from the antibodies and require immediate treatment.

How often is it done?

How often an ultrasound is done depends on the type of ultrasound, and what the doctor is looking for. A simple dating ultrasound, or general anatomy ultrasound is only done once. Doppler ultrasounds or biophysical profile ultrasounds are done more frequently (every couple of days if needed).

How is it done?

Ultrasound is a non-invasive, painless procedure. You will lie on your back on an exam table. The person performing the test will spread a gel on your abdomen and place a wand in the gel. The gel helps the wand transmit sound waves that will bounce off the baby to create a picture on the ultrasound machine. If it is very early in pregnancy, a vaginal ultrasound may be done. The procedure is the same, except that a slim wand is inserted into the vagina.

What do the numbers mean?

Your doctor will go over any numbers with you. Depending on the type of ultrasound you have, there are a variety of number possibilities.

What risks are there?

While most doctors agree that ultrasound is safe, it does carry some slight risks that you should be aware of. For most women with ISO, these risks are nowhere close to the very real risk of the baby dying if not treated appropriately.

Ultrasounds can cause problems with high heat, cavitation, and acoustic streaming9. When fetuses move away from the stream of high-frequency sound waves, they may be feeling vibrations, heat or both. As the FDA warned in 2004, "ultrasound is a form of energy, and even at low levels, laboratory studies have shown it can produce physical effect in tissue, such as jarring vibrations and a rise in temperature." (12) What this means is that the baby does feel the ultrasound waves as vibrations and/or heat. Depending on the energy, they can also be heard by both mom and baby.

Tissues of the central nervous system are sensitive to damage by physical agents, such as heat and ultrasound. Exposure to pulsed spectral Doppler ultrasound can significantly heat biologic tissue because of the relatively high intensities used and the need to hold the beam stationary during examinations. This has significant implications for sensitive neural tissue such as that exposed during spectral Doppler flow studies of fetal cerebral vessels.(13) The amount of ultrasound-induced intracranial heating increases with gestational age and the development of fetal bone; pulsed spectral Doppler ultrasound can produce biologically significant heating in the fetal brain; the rate of heating near bone is rapid, with approximately 75% of the maximum heating occurring within 30 s; blood flow has minimal cooling effect on ultrasound-induced heating of the brain when insonated with narrow focused clinical beams; the threshold for irreversible damage in the developing embryo and fetal brain is exceeded when a temperature increase of 4 degrees C is maintained for 5 min; an ultrasound exposure that produces a temperature increase of up to 1.5 degrees C in 120 s does not elicit measurable electrophysiologic responses in fetal brain; for some exposure conditions, the thermal index (TI), as used in the FDA-approved output display standard, underestimates the extent of ultrasound-induced intracranial temperature increase. (13)

There is also some correlation between Intrauterine Growth Retardation (IGR) and repeated ultrasound usage. In a study between two groups of women, one group (1415 women) had 1 ultrasound at 18 weeks, the others (1419) had 5 ultrasounds total, beginning at 18 weeks. The intensive group had a significantly higher intrauterine growth restriction which showed up as birth weights less than 10th percentile, and birth weights less than 3rd percentile10. A Follow up study was done on these children. Examinations were done at 1, 2, 3, 5, and 8 years of age on children born without congenital abnormalities and from singleton pregnancies (intensive group n=1362, regular group n=1352). The follow-up rate at 1 year was 85% (2310/2714) and at 8 years was 75% (2042/2714). By 1 year of age and thereafter, physical sizes were similar in the two groups. There were no significant differences indicating deleterious effects of multiple ultrasound studies at any age as measured by standard tests of childhood speech, language, behaviour, and neurological development. INTERPRETATION:

Exposure to multiple prenatal ultrasound examinations from 18 weeks' gestation onwards might be associated with a small effect on fetal growth but is followed in childhood by growth and measures of developmental outcome similar to those in children who had received a single prenatal scan. (11)

MCA Doppler Assessment

What is it?

A special type of doppler ultrasound, called a Middle Cerebral Artery (MCA)  scan, is used to detect fetal anemia. This is a doppler assessment of peak velocity in mid cerebral artery.

When is it done?

MCA scans are done before 35 weeks because after 35 weeks there is a higher risk of getting a false positive (saying baby is anemic when he actually isn't). However, new data suggests that MCA scans may be accurate enough to use up to 37 weeks.

Where is it done?

MCA scans can be done anywhere ultrasound scans are done as long as the machine (and technician) are capable.

Why is it done?

It is done to detect fetal anemia.

How often is it done?

How often an MCA is done depends on each individual case. We started out with one per month, but when our MoM numbers went up (see 'What do the numbers mean?'), we had one every 2 days. Some doctors do them every 2 weeks, every week, or twice a week, depending on your MoM values.

How is it done?

MCA scans are done on your belly just like any other ultrasound. There is a certain angle that the technician needs to get to measure the blood flow in the correct artery of the brain. You will probably see red or blue on the screen since the colors indicate blood flow. Not all technicians are as skilled as others, or as the doctor. You can have different numbers from different techs at the same time. It is always a good idea to go with the numbers from the most experienced person (frequently the doctor). They will usually take an average of 3-5 readings to make sure they get a full picture.

What do the numbers mean?

With an MCA scan, you will get PSV values. Ask for them if they aren't given, or look at the screen during the scan. These PSV values are then plugged into a formula to find your MoM number. You can get a great calculator here: . Alternate calculator:

A MoM of 1 is normal. 1.5 is generally considered anemic. More charts and data can be found in the section on Fetal Anemia.

After an intrauterine transfusion (IUT) the characteristics of fetal blood are altered because adult red cells are smaller and less rigid and they display an increased tendency for erythrocyte aggregation. Therefore it became pertinent to examine the usefulness of MCA PSV following IUT. But applying a change in the established cutoff level for MCA PSV from 1.50MoM (multiples of the median) in the fetus never transfused to 1.69MoM in previously transfused fetus may be of help.(16)

What risks are there?

There are no additional risks with an MCA scan. It is important to note that MCA scans are not fully accurate after a transfusion. It is not uncommon to get false high readings after a transfusion. See the section on Fetal Anemia for more information. There is also a greater chance of getting a false high MoM if the baby is moving or over 35 weeks.

Don't forget to get a copy of printable pages for keeping track of your results over on the info page. The printables are a collection of documents you can use to keep track of your own care. Print it out and take it with you to all appointments. It has places to record titers, PSV and MOM values, and more.

MCA scan with the PSV circled.

This contains the formula for how to calculate your MoM score.

Biophysical Profile (BPP)

What is it?

A Biophysical profile (BPP) is a part of the ultrasound that can be added on if the doctor chooses. It takes 30 minutes and looks at 4 main areas: breathing, gross body movements, muscle tone, and amniotic fluid.

When is it done?

Biophysical profiles can be done any time after the age of viability (24 weeks), but usually do not begin until after week 27.

Why is it done?

A biophysical profile is used to evaluate and monitor a baby's health. The goal of a biophysical profile is to prevent pregnancy loss and detect fetal hypoxia — when the baby is deprived of an adequate oxygen supply — early enough so that the baby can be delivered and not sustain permanent damage (7). Since this is always a risk with ISO pregnancies, most women will have at least one done.

How often is it done?

Biophysical profiles can be done once during pregnancy, or more frequently depending on each individual case. Some doctors have them done once a month, every week or twice a week near the end of pregnancy.

How is it done?

A Biophysical profile is done just like a regular ultrasound, except they look for a couple of extra things and assign a score to the baby.

What do the numbers mean?

There are 8 points possible, 2 points are assigned for each category. It is an all or nothing score (2 points or 0 points).

Breathing: 1 or more episodes of fetal breathing lasting at least 30 seconds.

Gross Body Movement: 3 or more discrete body or limb movements.

Fetal Tone: One or more episodes of active extension and flexion of an extremity or opening and closing of the hand.

Amniotic Fluid Volume: A 2 x 2 centimeter pocket of amniotic fluid is present.

In this case, a perfect score is 8. Some places add on an extra category to give a possibility of 10 points. If so, they are adding a Non Stress Test (NST).

NST: 2 or more heart rate increases of at least 15 beats per minute. Each increase lasts 15 seconds or more and is seen with movement8.  

8 to 10 points means that your baby is healthy. A score of 6 to 8 points means that you may need to be retested in 12 to 24 hours. A score of 4 or less may mean the baby is having problems. Further testing will be recommended (8). A low score may mean that you need extra monitoring, early, or immediate delivery (7).

In this photo you can see the BPP results. The top has the pertinent info such as gestational age, estimated due date, etc. The middle contains the measurements of amniotic fluid (in this case, they were low at 8.4). Fetal heart rate is listed, as well as the final BPP results. There were 4 categories included: fetal tone, fetal breathing, fetal movements, and amniotic fluid.

Nonstress Test (NST)

What is it?

A nonstress test is a monitoring tool where they put 2 “buttons” on mom's belly to monitor heart rate and uterine contractions. It is basically just monitoring baby's heart rate for an extended amount of time, usually about 20-30 minutes.

When is it done?

Non-stress tests can be done anytime after 26 weeks.

Where is it done?

NSTs are done in the doctor's office or hospital.

Why is it done?

NSTs are done to monitor baby's heart rate and to see if the baby is reactive or if additional tests are needed to check on baby's health.

How often is it done?

Depending on the doctor and situation, NSTs can be done every 3 days, or only when decreased movement is noticed.

How is it done?

Two sensors are put on the belly and secured with 1 or 2 bands. The sensors are hooked up to a machine that will print out a graph with baby's heart rate, mom's heart rate, baby's movements, and uterine contractions.

What do the numbers mean?

If the line is relatively flat, it is considered nonreactive. This is sometimes referred to as baby sleeping. They will try and wake baby up by having mom drink juice or eat something. They can also use a buzzer on the belly to startle the baby and get movement. In order to pass the NST (reactive), you need 2 or more heart rate increases of at least 15 beats per minute. Each increase lasts 15 seconds or more and is seen with movement8.  

In the photos below, the baby's heart rate is the top line, mom's heart rate is the faint middle line, the dotted line is the baby's movement (more visible in the reactive picture), and the bottom line is the uterine contractions.

Nonreactive or asleep


Additional Info

Because iso babies can gradually become anemic, they can compensate for the anemia. This makes it so that it is possible for baby to still pass an NST and still be anemic. It's important to always pay attention to movement, and notify your care provider and/or labor and delivery if you notice decreased movement.


Invasive Tests


What is it?

Amniocentesis (amnio) is a procedure where they remove some of the fluid from around baby for testing.

When is it done?

Amniocentesis is usually done between 14 and 20 weeks, but can be done earlier or later in ISO cases.

Where is it done?

Amniocentesis is usually done in the hospital, but some doctor's offices and outpatient facilities are able to do it as well.

Why is it done?

Amniocentesis is done to check baby's blood type and to check for antigens. It is also used to measure the level of bilirubin and to check for lung maturity before delivery.

How often is it done?

Amniocentesis is usually done only once. Occasionally a second amnio will be done to check for lung maturity if early delivery is needed.

How is it done?

The doctor will perform an ultrasound to see where the baby is and to guide the needle. He will clean your abdomen and insert a thin, hollow needle into the uterus. A syringe will be used to take a small amount of fluid and the needle will be removed. You will need to stay still during the procedure. You may notice a stinging sensation or some cramping. The procedure usually takes about 20-30 minutes. Afterwards, baby will be monitored for a few minutes to check on heart rate. Talk with your doctor to find out about any physical restrictions and warning signs to watch for.14

What do the numbers mean?

There are 2 different curves used to plot the values for bilirubin.

Lily Curve – there are 2 versions of the lily curve. The original was for after 27 weeks, however since the bili tends to peak at 23-25 weeks' gestation in unaffected fetuses, a modified zone was developed5.

Queenan curve - “Another curve was developed by Queenan for management of pregnancies before 27 weeks' gestation. A recent comparison of the curves found the Queenan curve to be superior to the Liley curve in overall sensitivity, specificity, and accuracy.” (5)

What risks are there?

Amniocentesis has replaced chorionic villus sampling (CVS) in ISO cases. It is considered safer, has a lower risk of increasing antibodies, and more accurately addresses the information that doctors need to know. Amniocentesis carries some risks include miscarriage (1 in 300-500 in the 2nd trimester, possibly higher if done earlier), needle injury (if baby moves into the path of the needle), leaking amniotic fluid, sensitization (if negative for antibodies) or increase in antibodies, and infection.  For some women, the risks of amniocentesis are not worth it. It is possible to work with your doctor to have additional monitoring and treat the pregnancy as if it was affected by ISO and avoid the amnio altogether.

Standard Liley Curve 27-42 Weeks

We know that's a lot to take in, but try not to be overwhelmed. We try to cover as much as possible so you can be informed about both current and past testing options. Individual doctors may or may not use some of these things. They choose the care plan that they (and you) are most comfortable with; we just provide information for your personal understanding about what has been used successfully in the literature.